Note: This page contains sample records for the topic active geothermal systems from Science.gov.
While these samples are representative of the content of Science.gov,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of Science.gov
to obtain the most current and comprehensive results.
Last update: August 15, 2014.
1

Geothermal systems  

NASA Technical Reports Server (NTRS)

Several tasks of JPL related to geothermal energy are discussed. The major task is the procurement and test and evaluation of a helical screw drive (wellhead unit). A general review of geothermal energy systems is given. The presentation focuses attention on geothermal reservoirs in California, with graphs and charts to support the discussion. Included are discussions on cost analysis, systems maintenance, and a comparison of geothermal and conventional heating and cooling systems.

Mohl, C.

1978-01-01

2

Geothermal materials development activities  

SciTech Connect

This ongoing R&D program is a part of the Core Research Category of the Department of Energy/Geothermal Division initiative to accelerate the utilization of geothermal resources. High risk materials problems that if successfully solved will result in significant reductions in well drilling, fluid transport and energy conversion costs, are emphasized. The project has already developed several advanced materials systems that are being used by the geothermal industry and by Northeastern Electric, Gas and Steam Utilities. Specific topics currently being addressed include lightweight C0{sub 2}-resistant well cements, thermally conductive scale and corrosion resistant liner systems, chemical systems for lost circulation control, elastomer-metal bonding systems, and corrosion mitigation at the Geysers. Efforts to enhance the transfer of the technologies developed in these activities to other sectors of the economy are also underway.

Kukacka, L.E.

1993-06-01

3

Modeling the thermal evolution of an active geothermal system  

NASA Astrophysics Data System (ADS)

Temperature inversions at shallow to moderate depths have been observed commonly in boreholes drilled in geothermal areas. The inversions result from thermal disequilibria generated by steam and/or hydrothermal fluids invading shallow horizontal, or sub-horizontal fractures, or permeable horizons, from a deep vertical, or sub-vertical feeder-fracture. Subsurface distribution of temperatures in Momotombo geothermal area of Nicaragua, Central America, indicates that the anomaly is generated by steam and water, convecting in a narrow feeder-fracture-zone located at the western edge of the field. The north-trending zone of the feeder-fracture is bound on the west by the area of massive, impermeable andesitic rocks, and is capped by an impermeable, approximately 300 m. thick silica-cap, which seals if from the ground surface. The thermal fluids penetrate a system of horizontal, or sub-horizontal fractures, extending east of the feeder-fracture beneath the silica cap. The flow of thermal fluids eastward through the system of the horizontal, or sub-horizontal fractures is generating a plume-like geothermal anomaly, which is expressed by the temperature inversion zone pervasive in the boreholes to the east of the feeder-fracture. A time-dependant model for a semi-infinite half-space (z > 0) in contact with a hot, well stirred, isotropic fluid flowing through an aquifer overlain by a finite space of constant thickness is solved for the data collected from the Momotombo geothermal boreholes. Curve fitting between the simulated and observed temperature/depth profiles suggests that the thermo-tectonic events which caused the present-day Momotombo hydrothermal system occurred approximately 5,500 years ago, following development of vertical, or subvertical fractures along a N5°E trending faultline. Hot fluids emerging from these fractures move eastward through a system of horizontal, or sub-horizontal fractures, with a velocity of 11 to 20 m/yr.

Eckstein, Y.; Maurath, G.; Ferry, R. A.

1985-12-01

4

National Geothermal Data System  

NASA Astrophysics Data System (ADS)

The goal of the U.S. Department of Energy's National Geothermal Data System is to design, build, implement, deploy and populate a national, sustainable, distributed, interoperable network of data and service (application) providers. These providers will develop, collect, serve, and maintain geothermal-relevant data that operates as an integral component of NGDS. As a result the geothermal industry, the public, and policy makers will have access to consistent and reliable data, which in turn, reduces the amount of staff time devoted to finding, retrieving, integrating, and verifying information. With easier access to information, the high cost and risk of geothermal power projects (especially exploration drilling) is reduced. Five separate NGDS projects provide the data support, acquisition, and access to cyber infrastructure necessary to reduce cost and risk of the nation's geothermal energy strategy and US DOE program goals focused on the production and utilization of geothermal energy. The U.S DOE Office of Energy Efficiency and Renewable Energy Geothermal Technologies Program is developing the knowledge and data foundation necessary for discovery and development of large-scale energy production while the Buildings Technology Program is focused on other practical applications such as direct use and residential/commercial ground source heat pumps. The NGDS provides expanded reference and resource data for research and development activities (a subset of the US DOE goals) and includes data from across all fifty states and the nation's leading academic geothermal centers. Thus, the project incorporates not only high-temperature potential but also moderate and low-temperature locations incorporating US DOE's goal of adding more geothermal electricity to the grid. The program, through its development of data integration cyberinfrastructure, will help lead to innovative exploration technologies through increased data availability on geothermal energy capacity. Finally, the project will contribute new data from previously unexplored locations. NGDS is being built using the US Geoscience Information Network (US GIN) data integration framework to promote interoperability across the Earth sciences community and with other emerging data integration and networking efforts.

Anderson, A. F.; Cuyler, D.; Snyder, W. S.; Allison, M. L.; Blackwell, D. D.; Williams, C. F.

2011-12-01

5

Geothermal Activities in Central America.  

National Technical Information Service (NTIS)

The Agency for International Development is funding a new program in energy and minerals for Central America. Geothermal energy is an important component. A country-wide geothermal assessment has started in Honduras, and other assessment activities are in...

J. T. Whetten R. J. Hanold

1985-01-01

6

Origin and Distribution of Thiophenes and Furans in Gas Discharges from Active Volcanoes and Geothermal Systems  

PubMed Central

The composition of non-methane organic volatile compounds (VOCs) determined in 139 thermal gas discharges from 18 different geothermal and volcanic systems in Italy and Latin America, consists of C2–C20 species pertaining to the alkanes, alkenes, aromatics and O-, S- and N-bearing classes of compounds. Thiophenes and mono-aromatics, especially the methylated species, are strongly enriched in fluids emissions related to hydrothermal systems. Addition of hydrogen sulphide to dienes and electrophilic methylation involving halogenated radicals may be invoked for the formation of these species. On the contrary, the formation of furans, with the only exception of C4H8O, seems to be favoured at oxidizing conditions and relatively high temperatures, although mechanisms similar to those hypothesized for the production of thiophenes can be suggested. Such thermodynamic features are typical of fluid reservoirs feeding high-temperature thermal discharges of volcanoes characterised by strong degassing activity, which are likely affected by conspicuous contribution from a magmatic source. The composition of heteroaromatics in fluids naturally discharged from active volcanoes and geothermal areas can then be considered largely dependent on the interplay between hydrothermal vs. magmatic contributions. This implies that they can be used as useful geochemical tools to be successfully applied in both volcanic monitoring and geothermal prospection.

Tassi, Franco; Montegrossi, Giordano; Capecchiacci, Francesco; Vaselli, Orlando

2010-01-01

7

Cordon Caulle: an active volcanic-geothermal extensional system of Southern Andes of Chile  

NASA Astrophysics Data System (ADS)

Cordon Caulle (CC; 40.5° S) is an active volcanic-geothermal system of the Southern Volcanic Zone (SVZ; 37°-44°S). Morphologically, the CC system is a 6 km x 13 km volcanic plateau bordered by NW-trending structures, limited by Puyehue Volcano to the SE and by Caldera Nevada Caldera to the NW. While the SVZ is dominantly basaltic, CC is unique in that it has produced a wide compositional spectrum from basalt to rhyolite. The most recent volcanic activity of Puyehue-CC (last 70 ky) is dominantly silicic, including two historic fissure eruptions (1921-1922; 1960) and a recent central eruption from Puyehue Volcano (2011). Abnormally silicic volcanism was formerly attributed to a localized compression and long-term magma residence and differentiation, resulting from the NW orientation of underlying CC structures with respect to a NE-oriented ?1 (linked to regional strike-slip stress state). However, later studies, including examination of morpho-tectonic features; detailed structural analysis of the 1960 eruption (triggered by Mw 9.5 1960 Chilean Earthquake); InSAR deformation and gravity surveys, point to both historic and long-term extension at CC with ?hmax oriented NNW to NW. The pre-2011 (i.e. Puyehue Volcano eruption) geothermal features of CC included boiling hot springs and geysers (Caldera Nevada) and fumaroles (CC and Puyehue Volcano). Both water and gas chemistry surveys were undertaken to assess the source fluid composition and equilibrium temperature. The combination of water and gas geothermometers led to a conceptual model of a stratified geothermal reservoir, with shallow, low-chloride, steam-heated aquifers equilibrated at temperatures between 150°-180°C, overlying a deeper, possibly dominated reservoir with temperatures in excess of 280°C. Gas chemistry also produced the highest He ratios of the SVZ, in agreement with a relatively pure, undiluted magmatic signature and heat source fueling the geothermal system. Other indicators such as N2/Ar ratios indicated two sources of gases: a geothermal source (i.e. associated with benign, neutral geothermal fluids) at the centre of the CC, and a more volcanic-magmatic (i.e. associated with acidic, oxidising fluids) source towards the SE (Puyehue Volcano), in agreement with the presence of an active volcanic system. The combination of silicic volcanism, extension and high-temperature geothermal activity of CC pose some resemblance to high-temperature geothermal systems of the Taupo Volcanic Zone, North Island, New Zealand. In this setting, recent studies show that rifting (i.e. extension) can be a magma-assisted process. In a similar fashion, I hypothesize that a deep (> 2 km), NW-elongate magma reservoir can account for the development of NW-trending structures at CC, and the existence of central volcanism at both ends of the CC.

Sepulveda, F.

2013-05-01

8

Heat transfer in geothermal systems  

Microsoft Academic Search

Theoretical and experimental investigations of convective heat transfer in geothermal systems are reviewed. The governing equations for such heat transfer in geothermal systems are examined, along with heat transfer in hot-water, water-steam two-phase, and geopressured geothermal systems. Lumped-parameter analyses for predicting averaged reservoir characteristics during production are considered, heat transfer in other geothermal systems (e.g., dry hot rock and magma)

P. Cheng

1978-01-01

9

Geothermal Systems for School.  

ERIC Educational Resources Information Center

Describes an award-winning school heating and cooling system in which two energy-efficient technologies, variable-flow pumping and geothermal heat pumps, were combined. The basic system schematic and annual energy use and cost savings statistics are provided. (GR)

Dinse, David H.

1998-01-01

10

Geothermal activities in Central America  

Microsoft Academic Search

The Agency for International Development is funding a new program in energy and minerals for Central America. Geothermal energy is an important component. A country-wide geothermal assessment has started in Honduras, and other assessment activities are in progress or planned for Costa Rica, El Salvador, Guatemala, and Panama. Instrumentation for well logging has been provided to Costa Rica, and a

J. T. Whetten; R. J. Hanold

1985-01-01

11

Lassen geothermal system  

Microsoft Academic Search

The Lassen geothermal system consists of a central vapor-dominated reservoir underlain by hot water that discharges peripherally at lower elevations. The major thermal upflow at Bumpass Hell (elevation 2500 m) displays numerour superheated fumaroles, one of which in 1976 was 159°C. Gas geothermometers from the fumarole areas and water geothermometers from boiling Cl-bearing waters at Morgan Hot Springs (elevation 1530

L. J. P. Muffler; N. L. Nehring; A. H. Truesdell; C. J. Janik; M. A. Clynne; J. M. Thompson

1982-01-01

12

Geothermal hot water system  

SciTech Connect

Geothermal hot water system including a hot water tank and a warm water tank which are heated independently of each other by a close loop freon system. The closed loop freon system includes a main condenser which heats water for the warm water tank and a super-heated condenser which heats water for the hot water tank, and where the freon passes through a water evaporator which is heated by water such as from a well or other suitable source. The water evaporator in the closed loop freon system passes the water through but no environmental change to the water. An electrical circuit including aquastats in the warm water tank connected therethrough controls operation of the closed loop freon system including respective pumps on the super-heated condenser and main condenser for pumping water. Pumps pump water through the main condenser for the warm tank and through the super-heated condenser for the hot tank. The system provides for energy conservation in that the head pressure of the compressor is kept in the lower operating ranges as determined by the discharge flow of the main condenser which varies by the head pressure and temperature flow control which varies by temperature. The geothermal hot water system uses a least amount of energy in heating the water in the hot tank as well as the warm tank.

Dittell, E.W.

1983-05-10

13

Geothermal heating systems for greenhouses  

Microsoft Academic Search

Ways to utilize low-temperature geothermally heated water for a flow-through system are presented. The geothermal energy used for this system is the waste heat discharged from space heating 500,000 square feet of floor space at Oregon Institute of Technology with geothermal water pumped directly from the campus wells. The information collected and analyzed is from data developed from operating a

J. F. Silva; W. C. Johnson

1980-01-01

14

National Geothermal Data System (NGDS)  

DOE Data Explorer

The National Geothermal Data System (NGDS) is a DOE-funded distributed network of databases and data sites. Much of the risk of geothermal energy development is associated with exploring for, confirming and characterizing the available geothermal resources. The overriding purpose of the NGDS is to help mitigate this up-front risk by serving as a central gateway for geothermal and relevant related data as well as a link to distributed data sources. Assessing and categorizing the nation's geothermal resources and consolidating all geothermal data through a publicly accessible data system will support research, stimulate public interest, promote market acceptance and investment, and, in turn, the growth of the geothermal industry. Major participants in the NGDS to date include universities, laboratories, the Arizona Geological Survey and Association of American State Geologists (Arizona Geological Survey, lead), the Geothermal Resources Council, and the U.S. Geological Survey. The Geothermal Energy Association is collaborating with the NGDS to insure that it meets the needs of the geothermal industry.

15

Earthquake Swarm Activity Beneath the Tokaanu-Waihi Geothermal System, Lake Taupo, New Zealand  

SciTech Connect

The hypocenters of 4 earthquake swarms (total of 54 events), recorded with a local network between 1986 April and 1987 January, occur within upper crustal rocks of the deeper Tokaanu-Waihi geothermal reservoir; all the events had a magnitude M{sub L} {le} 3.2. Most foci are aligned along two NW-trending basement fault structures along which young rhyodacitic extrusions can be found. The swarm activity has been interpreted in terms of injections into basement fractures of magma from deeper chambers (dyke injection swarm activity).

Hochstein, M.P.; Sherburn, S.; Tikku, J.

1995-01-01

16

Reno Industrial Park geothermal district heating system  

SciTech Connect

Ten miles south of Reno, on U.S. 395 near the junction of the road to historic Virginia City, is Steamboat Hot Springs, a popular stop for travelers since the mid-1800s. Legend has it that Mark Twain named the geothermal area because it looked and sounded like a chugging Mississippi River paddle-wheeler. It is said when he first saw the steam rising from the ground he exclaimed, {open_quotes}Behold! A Steamboat in the desert.{close_quotes} Over the years, the area has been used for its relaxing and curative qualities by Indians, settlers, and geothermal experts. Since the mid-1980s five geothermal power plants have been built at Steamboat Springs and in December 1996 it was announced that the proposed largest geothermal district heating system in the U.S. would supply an industrial park in the area. The active geothermal area is located within the north-south trending graben like trough between the Carson and Virginia Ranges at the southern end of Truckee Meadows. Hot springs and other geothermal features occur over an area of about one square mile. The mid-basin location is controlled by faulting more or less parallel to the major mountain-front faults. It is believed that the heat source for the system is a cooling magmatic body at depth. The Steamboat geothermal area consists of a deep, high-temperature (215{degrees}C to 240{degrees} C) geothermal system, a shallower, moderate-temperature (160{degrees}C to 18{degrees} C) system, and a number of shallow low-temperature (30{degrees}C to 80{degrees}C) subsystems. The higher temperature systems are used for electric-power generation. It is proposed that the exit fluids from the electric power plants be used for the geothermal district heating system.

Lienau, P.J.

1997-04-01

17

Arsenic geochemistry in geothermal systems  

Microsoft Academic Search

Arsenic is an important trace constituent in geothermal fluids, ranging in concentration from less than 0.1 to nearly 50 ppm. An evaluation of published fluid analyses from geothermal systems indicates that the As content of the reservoir fluids varies inversely with P\\/sub HâS\\/ and directly with temperature. Aqueous As species occur in two oxidation states, As\\/sup III\\/ and As\\/sup V\\/.

J. M. Ballantyne; J. N. Moore

1988-01-01

18

Reaction modeling in geothermal systems  

NASA Astrophysics Data System (ADS)

Natural volcanic geothermal systems are open systems in term of matter and energy. Such systems are complex to model in terms of fluid chemistry, fluid flow and energy budget. Reaction modeling may be used to gain insight and possibly quantify chemical processes occurring within a system, for example fluid-fluid and fluid-rock interaction. Methods have been developed within the WATCH (Bjarnason, 1994; Arnórsson et al., 2007) and PHREEQC (Parkhurst and Appelo, 1999) programs to simulate reactions of multicomponent and multiphase systems to 300°C. The models include boiling and phase segregation (open system boiling), fluid-fluid mixing and fluid-rock interaction (gas-water-rock interaction). The models have been applied to quantify processes within the Hellisheidi geothermal system, Iceland. Open system boiling and fluid-rock interaction were simulated as a function of temperature, initial fluid composition and extent of reaction (T-X-?). In addition the interactions of magmatic gases with geothermal fluids and rocks were modeled. In this way various component behavior has been traced within the geothermal system and compared with observations of fluid composition and mineralogy. In addition, the reaction models have been used to evaluate the geochemical feasibility and best conditions of gas (CO2 and H2S) and waste water injection into geothermal system.

Stefansson, A.

2012-12-01

19

Lassen geothermal system  

SciTech Connect

The Lassen geothermal system consists of a central vapor-dominated reservoir underlain by hot water that discharges peripherally at lower elevations. The major thermal upflow at Bumpass Hell (elevation 2500 m) displays numerour superheated fumaroles, one of which in 1976 was 159/sup 0/C. Gas geothermometers from the fumarole areas and water geothermometers from boiling Cl-bearing waters at Morgan Hot Springs (elevation 1530 m; 8 km south of Bumpass Hell) and from 176/sup 0/C waters in a well 12 km southeast of Bumpass Hell both indicate 230 to 240/sup 0/C for the deep thermal water. With increasing distance from Bumpass Hell, gases are progressively depleted in H/sub 2/S relative to CO/sub 2/ and N/sub 2/, owing to oxidation of H/sub 2/S to pyrite, sulfur, and sulfates and to dilution with atmospheric N/sub 2/. H/sub 2/O/gas ratios and degree of superheat of fumaroles can be explained by mixing of steam of maximum enthalpy (2804 J g/sup -1/) with near-surface water and with the condensate layer overlying the vapor-dominated reservoir.

Muffler, L.J.P.; Nehring, N.L.; Truesdell, A.H.; Janik, C.J.; Clynne, M.A.; Thompson, J.M.

1982-01-01

20

Investigating Geothermal Activity, Volcanic Systems, and Deep Tectonic Tremor on Akutan Island, Alaska, with Array Seismology  

NASA Astrophysics Data System (ADS)

In addition to hosting one of the most active volcanoes in the Aleutian Arc, Akutan Island, Alaska, is the site of a significant geothermal resource within Hot Springs Bay Valley (HSBV). We deployed 15 broadband (30 s to 50 Hz) seismometers in and around HSBV during July 2012 as part of an effort to establish a baseline for background seismic activity in HSBV prior to geothermal production on the island. The stations recorded data on-site and were retrieved in early September 2012. Additional targets for the array include the tracking of deep tectonic tremor known to occur within the Aleutian subduction zone and the characterization of volcano-tectonic (VT) and deep long period (DLP) earthquakes from Akutan Volcano. Because 13 of the stations in the array sit within an area roughly 1.5 km by 1.5 km, we plan to apply methods based on stacking and beamforming to analyze the waveforms of extended signals lacking clear phase arrivals (e.g., tremor). The average spacing of the seismometers, roughly 350 m, provides sensitivity to frequencies between 2-8 Hz. The stacking process also increases the signal-to-noise ratio of small amplitude signals propagating across the array (e.g., naturally occurring geothermal seismicity). As of August 2012, several episodes of tectonic tremor have been detected in the vicinity of Akutan Island during the array deployment based on recordings from nearby permanent stations operated by the Alaska Volcano Observatory (AVO). This is the first small-aperture array deployed in the Aleutian Islands and the results should serve as a guide for future array deployments along the Aleutian Arc as part of the upcoming EarthScope and GeoPRISMS push into Alaska. We demonstrate the power of array methods based on stacking at Akutan Volcano using a sequence of DLP earthquakes from June 11, 2012 that were recorded on the permanent AVO stations. We locate and characterize the lowest frequency portion of the signals at 0.5 Hz. At these low frequencies, the traditional "sparse" local network at Akutan effectively becomes a small-aperture array relative to the wavelength. We exploit the coherency among the stations and locate the DLPs by using a novel stacking method. The crux of the method involves scanning over all possible source locations and relative polarity combinations between the local stations to find the one that maximizes the stacked power at a well-defined region in the subsurface. As a result, the method is applicable even in the presence of mixed polarities. We discover that two of the stations at Akutan have DLP waveforms with opposite polarities compared to the other stations. Accounting for this polarity variation gives a DLP source location at 10 km depth, to the west-southwest of the Akutan summit caldera. These results give clear evidence for non-isotropic radiation patterns associated with DLPs and show the promise of array methods based on waveform stacking for providing future insights into the origin of volcanic as well as geothermal and tectonic seismicity.

Haney, M. M.; Prejean, S. G.; Ghosh, A.; Power, J. A.; Thurber, C. H.

2012-12-01

21

Evolution of an active magmatic-geothermal system at The Geysers, California  

NASA Astrophysics Data System (ADS)

The Geysers geothermal system initially developed at 1.1 to 1.2 Ma in response to the intrusion of a hypabyssal granitic pluton exceeding 100 km2 in area. The geothermal system, which is developed in Mesozoic metagraywacke and the underlying granite, is currently vapor-dominated and produces only dry steam. Mineralogic, fluid inclusion and isotopic data demonstrate the current vapor-dominated regime evolved from a liquid-dominated system. Within 600 m of the pluton, the rocks were altered to a biotite hornfels that is cut by veins of tourmaline + biotite + actinolite + clinopyroxene + albitic plagioclase. Fluid inclusions trapped in the vein minerals record maximum homogenization temperatures near 380°C and salinities up to 44 wt% NaCl equivalent. With increasing distance from the pluton, the veins are characterized by actinolite + epidote, epidote + chlorite, and finally calcite. Quartz and adularia are commonly observed in these veins. Fluid inclusions trapped at a distance of 1750 m from the intrusion record temperatures up to 305°C and salinities of 5 wt% NaCl equivalent. Whole-rock oxygen isotope data indicates the metagraywacke and granitic reservoir rocks were isotopically exchanged with meteoric water during the liquid dominated phase of the system. The transition from liquid- to vapor-dominated conditions occurred at 0.25 to 0.28 Ma, based on 40Ar/39Ar spectrum dating of adularia. As the liquids boiled off, bladed calcite, chalcedony, quartz and adularia were deposited. Vapor-rich inclusions dominate the fluid inclusion populations of many samples. Low salinity liquid-rich fluid inclusions (0.0 - 0.4 wt% NaCl equivalent), interpreted to consist primarily of steam condensate, suggest that widespread boiling and vapor-dominated convection cells had formed in the upper part of the present-day reservoir by the time temperatures had dropped to approximately 250° - 265°C. Subsequent inflow of relatively cool marginal meteoric waters resulted in the deposition of calcite and the formation of low permeability seals around the reservoir. The present vapor-dominated system at The Geysers consists of two distinct, hydraulically connected steam reservoirs. The upper, normal vapor-dominated reservoir is found throughout the field. Temperatures within this reservoir are isothermal and close to 240°C. The lower high temperature reservoir occurs within the biotite hornfels in the northern half of the field. Measured temperatures follow a conductive gradient and range from about 240°C to 400°C. Pressures are vaporstatic in both reservoirs. The high temperature reservoir in the Northwest Geysers is the youngest part of the system. Here newly formed biotite hornfels is being heated by a recent magmatic intrusion interpreted to have been emplaced between 5,000 and 10,000 y bp. This portion of the deep Northwest reservoir is characterized by low permeabilities and the highest measured temperatures and 3He/4He ratios (~7-9.6Ra) encountered in the field. In contrast to other parts of the system, the biotite hornfels in the Northwest Geysers has not been isotopically exchanged with meteoric water.

Moore, J. N.; Walters, M.

2012-12-01

22

Condensation Processes in Geothermal Systems  

NASA Astrophysics Data System (ADS)

We model condensation processes in geothermal systems to understand how this process changes fluid chemistry. We assume two processes operate in geothermal systems: 1) condensation of a vapor phase derived by boiling an aqueous geothermal fluid into a cool near surface water and 2) condensation of a magmatic vapor by a deep circulating meteoric thermal fluid. It is assumed that the condensation process has two stages. Initially the condensing fluid is under saturated in gaseous species. Condensation of the vapor phase continues until the pressure on the fluid equals the sum of the partial pressures of water and the dissolved gaseous species. At that time bubbles flux through the condensing fluid. In time the fluid and fluxing gas phase come to equilibrium. Calculation shows that during the second stage of the condensation process the liquid phase becomes enriched in more soluble gaseous species like CO2 and H2S, and depleted in less soluble species like CH4 and N2. Stage 2 condensation processes can therefore be monitored by ratios of more and less condensable species like CO2/N2. Condensation of vapor released by boiling geothermal fluids results in liquids with high concentrations of H2S and CO2 like is seen in geothermal system steam-heated waters. Condensation of a magmatic vapor into circulating meteoric water has been proposed, but not well demonstrated. We compare to our models the Cerro Prieto, Mexico gas analysis data set collected over twelve years time by USGS personnel. It was assumed for modeling that the Cerro Prieto geothermal fluids are circulating meteoritic fluids with N2/Ar ratios about 40 to which is added a magmatic vapor with N2/Ar ratio = 400. The Cerro Prieto analyses show a strong correlation between N2/Ar and CO2/N2 as predicted by calculation. Two dimensional image plots of well N2/Ar + CO2/N2 show a bull's-eye pattern on the geothermal field. Image plots of analyses collected over a year or less time show N2/Ar and CO2/N2 hot spots. Plotting data for individual wells show a hysteresis like loops on time vs. CO2/N2 diagrams. Our analysis demonstrates that condensation of magmatic vapor into convecting meteoric waters is a viable process. Condensation explains variations in Cerro Prieto geothermal system gas chemistry and is compatible with helium isotope data. Locally condensation appears to wax and wane over a time periods of about 10 years.

Norman, D. I.; Moore, J. N.

2005-12-01

23

Boise geothermal district heating system  

SciTech Connect

This document describes the Boise geothermal district heating project from preliminary feasibility studies completed in 1979 to a fully operational system by 1983. The report includes information about the two local governments that participated in the project - the City of Boise, Idaho and the Boise Warm Springs Water District. It also discusses the federal funding sources; the financial studies; the feasibility studies conducted; the general system planning and design; design of detailed system components; the legal issues involved in production; geological analysis of the resource area; distribution and disposal; the program to market system services; and the methods of retrofitting buildings to use geothermal hot water for space heating. Technically this report describes the Boise City district heating system based on 170/sup 0/F water, a 4000 gpm production system, a 41,000 foot pipeline system, and system economies. Comparable data are also provided for the Boise Warm Springs Water District. 62 figs., 31 tabs.

Hanson, P.J.

1985-10-01

24

Geothermal Data from the National Geothermal Data System (NGDS)  

DOE Data Explorer

The National Geothermal Data System (NGDS) is a distributed data system providing access to information resources related to geothermal energy from a network of data providers. Data are contributed by academic researchers, private industry, and state and federal agencies. Built on a scalable and open platform through the U.S. Geoscience Information Network (USGIN), NGDS respects data provenance while promoting shared resources.Since NGDS is built using a set of open protocols and standards, relying on the Open Geospatial Consortium (OGC) and International Organization for Standardization (ISO), members of the community may access the data in a variety of proprietary and open-source applications and software. In addition, developers can add functionality to the system by creating new applications based on the open protocols and standards of the NGDS. The NGDS, supported by the U.S. Department of Energy’s Geothermal Technology Program, is intended to provide access to all types of geothermal data to enable geothermal analysis and widespread public use in an effort to reduce the risk of geothermal energy development [copied from http://www.geothermaldata.org/page/about]. See the long list of data contributors at http://geothermaldata.org/page/data-types-and-contributors#data-contributors.

25

The Iceland Deep Drilling Project: (III) Evidence for amphibolite grade contact metamorphism in an active geothermal system  

NASA Astrophysics Data System (ADS)

One of the scientific goals of the Iceland Deep Drilling Project is to reach the depths of transition from greenschist to amphibolite grade metamorphism in an active geothermal system. The deepest borehole to date in the Reykjanes system is RN-17, which was drilled to a depth of 3082 m. This well had been considered as a candidate for deepening by the IDDP until it collapsed during a flow test in November 2005. Temperatures in the lower portion of the borehole were never recorded due to an obstruction at 2100 m depth, but are estimated to be approximately 340°C. Epidote, albite, and actinolite are ubiquitous within pillow basalt, hyaloclastite, and in veins, implying that greenschist grade conditions have been attained throughout much of the well below approximately 1200 m. Intrusive lithologies constitute approximately 50% of the observed cuttings between 2600 and 2700 m. These intrusive rocks have produced small, but recognizable contact metamorphic effects characterized by granoblastic hornfels consisting of amphibolite grade assemblages of quartz + anorthite + diopside + magnetite + titanite. These have, in turn, been locally cut by actinolite veins, presumably reflective of the present-day, thermal state of the hydrothermal system at these depths. Based on their siliceous bulk composition, we believe the hornfels represent the thermally- recrystallized products of earlier-formed, hydrothermal veins consisting of quartz, epidote, and actinolite. The metamorphic plagioclase is distinctly more anorthitic (An90 to An98) than igneous plagioclase in adjacent mafic intrusives (An33 to An80) and also exhibits consistently lower Mg content and higher iron (up to 2.07 wt.% as Fe2O3). Stoichiometry implies that much of the iron in hydrothermal anorthite is Fe3+, which may imply recrystallization from precursor epidote under relatively oxidizing conditions. Diopside compositions (average Wo0.48En0.27Fs0.25) are consistently less calcic than hydrothermal clinopyroxenes found in quartz+epidote+actinolite veins, and are also distinct from igneous clinopyroxene. Their compositions imply that hornfelsic recrystallization may have occurred at temperatures as high as 600-650°C at depths of approximately 2.5 km. If the intrusive activity occurred during the last glaciation, hydrostatic pressures attending amphibolite metamorphism may have been as high as 300 bars. To our knowledge, this is the first time that texturally-equilibrated, amphibolite grade assemblages have been reported from an active geothermal system.

Marks, N.; Schiffman, P.; Zierenberg, R. A.; Franzson, H.

2008-12-01

26

Monitoring Biological Activity at Geothermal Power Plants  

SciTech Connect

The economic impact of microbial growth in geothermal power plants has been estimated to be as high as $500,000 annually for a 100 MWe plant. Many methods are available to monitor biological activity at these facilities; however, very few plants have any on-line monitoring program in place. Metal coupon, selective culturing (MPN), total organic carbon (TOC), adenosine triphosphate (ATP), respirometry, phospholipid fatty acid (PLFA), and denaturing gradient gel electrophoresis (DGGE) characterizations have been conducted using water samples collected from geothermal plants located in California and Utah. In addition, the on-line performance of a commercial electrochemical monitor, the BIoGEORGE?, has been evaluated during extended deployments at geothermal facilities. This report provides a review of these techniques, presents data on their application from laboratory and field studies, and discusses their value in characterizing and monitoring biological activities at geothermal power plants.

Peter Pryfogle

2005-09-01

27

Enhanced Geothermal Systems (EGS) R&D Program, Status Report: Foreign Research on Enhanced Geothermal Systems  

SciTech Connect

This report reviews enhanced geothermal systems (EGS) research outside the United States. The term ''enhanced geothermal systems'' refers to the use of advanced technology to extract heat energy from underground in areas with higher than average heat flow but where the natural permeability or fluid content is limited. EGS covers the spectrum of geothermal resources from low permeability hydrothermal to hot dry rock.

McLarty, Lynn; Entingh, Daniel

2000-09-29

28

Active metasomatism in the Cerro Prieto geothermal system, Baja California, Mexico: A telescoped low-pressure, low-temperature metamorphic facies series  

NASA Astrophysics Data System (ADS)

In the Cerro Prieto geothermal field, carbonate-cemented, quartzofeldspathic sediments of the Colorado River delta are being actively metasomatized into calc-silicate metamorphic rocks by reaction with alkali chloride brines between 200 and 370 °C, at low fluid and lithostatic pressures and low oxygen fugacities. Our petrologic investigations of drill cores and cuttings from more than 50 wells in this field identified a prograde series of zones that include as index minerals wairakite, epidote, prehnite, and clinopyroxene. Associated divariant mineral assemblages are indicative of a very low pressure, low-temperature metamorphic facies series spanning the clay-carbonate, zeolite, greenschist, and amphibolite facies. This hydro-thermal facies series, which is now recognized in other active geothermal systems, is characterized by temperature-telescoped dehydration and decarbonation. Its equivalent can now be sought in fossil hydrothermal systems.

Schiffman, P.; Elders, W. A.; Williams, A. E.; McDowell, S. D.; Bird, D. K.

1984-01-01

29

Fine-grained clay fraction (,0.2 {mu}m): An interesting tool to approach the present thermal and permeability state in active geothermal systems  

SciTech Connect

We have investigated by X-ray diffraction the very fine grained secondary minerals (< 0.2 {micro}m) developed in geothermal systems, in relation with their present thermal and permeability state. Because the smallest particles are the most reactive part of a rock, they are the youngest mineral phases of the geothermal fields. This study has been performed on two active geothermal fields: Milos field, Greece (130 < T < 320 C) and Chipilapa field, Salvador (90 < T < 215 C). In the Milos field, the mineralogical composition of the < 0.2 {micro}m clay fraction observed in the reservoir strongly differs from the overlying altered metamorphic schists in the presence of abundant quantities of saponite and talc/saponite interstratified minerals at unusually high temperature. These phases are considered to be kinetically control-led ''metastable'' minerals which rapidly evolve towards actinolite and talc for present temperatures higher than 300 C. Their occurrence is a good indicator of discharge in highly permeable zones. In the geothermal field of Chipilapa, the mineralogical composition of the < 0.2 {micro}m clay fractions fairly agrees with the temperatures presently measured in the wells, whereas several discrepancies may be pointed out from the compositions of coarser clay fractions (< 5 {micro}m) which contain minerals inherited from higher temperature stages. Permeable zones may be evidenced from an increase of expandable components in the interstratified minerals and a decrease of the coherent domain of the unexpandable clay particles (chlorite).

Patrier, P.; Papapanagiotou, P.; Beaufort, D.; Traineau, H.; Bril, H.

1992-01-01

30

Neutron imaging for geothermal energy systems  

SciTech Connect

Geothermal systems extract heat energy from the interior of the earth using a working fluid, typically water. Three components are required for a commercially viable geothermal system: heat, fluid, and permeability. Current commercial electricity production using geothermal energy occurs where the three main components exist naturally. These are called hydrothermal systems. In the US, there is an estimated 30 GW of base load electrical power potential for hydrothermal sites. Next generation geothermal systems, named Enhanced Geothermal Systems (EGS), have an estimated potential of 4500 GW. EGSs lack in-situ fluid, permeability or both. As such, the heat exchange system must be developed or engineered within the rock. The envisioned method for producing permeability in the EGS reservoir is hydraulic fracturing, which is rarely practiced in the geothermal industry, and not well understood for the rocks typically present in geothermal reservoirs. High costs associated with trial and error learning in the field have led to an effort to characterize fluid flow and fracturing mechanisms in the laboratory to better understand how to design and manage EGS reservoirs. Neutron radiography has been investigated for potential use in this characterization. An environmental chamber has been developed that is suitable for reproduction of EGS pressures and temperatures and has been tested for both flow and precipitations studies with success for air/liquid interface imaging and 3D reconstruction of precipitation within the core.

Bingham, Philip R [ORNL; Anovitz, Lawrence {Larry} M [ORNL; Polsky, Yarom [ORNL

2013-01-01

31

Enhanced Geothermal Systems (EGS) R&D Program: US Geothermal Resources Review and Needs Assessment  

SciTech Connect

The purpose of this report is to lay the groundwork for an emerging process to assess U.S. geothermal resources that might be suitable for development as Enhanced Geothermal Systems (EGS). Interviews of leading geothermists indicate that doing that will be intertwined with updating assessments of U.S. higher-quality hydrothermal resources and reviewing methods for discovering ''hidden'' hydrothermal and EGS resources. The report reviews the history and status of assessment of high-temperature geothermal resources in the United States. Hydrothermal, Enhanced, and Hot Dry Rock resources are addressed. Geopressured geothermal resources are not. There are three main uses of geothermal resource assessments: (1) They inform industry and other interest parties of reasonable estimates of the amounts and likely locations of known and prospective geothermal resources. This provides a basis for private-sector decisions whether or not to enter the geothermal energy business at all, and for where to look for useful resources. (2) They inform government agencies (Federal, State, local) of the same kinds of information. This can inform strategic decisions, such as whether to continue to invest in creating and stimulating a geothermal industry--e.g., through research or financial incentives. And it informs certain agencies, e.g., Department of Interior, about what kinds of tactical operations might be required to support such activities as exploration and leasing. (3) They help the experts who are performing the assessment(s) to clarify their procedures and data, and in turn, provide the other two kinds of users with a more accurate interpretation of what the resulting estimates mean. The process of conducting this assessment brings a spotlight to bear on what has been accomplished in the domain of detecting and understanding reservoirs, in the period since the last major assessment was conducted.

Entingh, Dan; McLarty, Lynn

2000-11-30

32

Sperry Low Temperature Geothermal Conversion System, Phase I and Phase II. Volume IV. Field activities. Final report  

SciTech Connect

This volume describes those activities which took place at the Sperry DOE Gravity Head plant site at the East Mesa Geothermal Reservoir near Holtville, California between February 1980, when site preparation was begun, and November 1982, when production well 87-6 was permanently abandoned. Construction activities were terminated in July 1981 following the liner collapse in well 87-6. Large amounts of program time manpower, materials, and funds had been diverted in a nine-month struggle to salvage the production well. Once these efforts proved futile, there was no rationale for continuing with the site work unless and until sufficient funding to duplicate well 87-6 was obtained. Activities reported here include: plant construction and pre-operational calibration and testing, drilling and completion of well 87-6, final repair effort on well 87-6, abandonment of well 87-6, and performance evaluation of well 87.6. (MHR)

Harvey, C.

1984-01-01

33

Small geothermal electric systems for remote powering  

SciTech Connect

This report describes conditions and costs at which quite small (100 to 1,000 kilowatt) geothermal systems could be used for off-grid powering at remote locations. This is a first step in a larger process of determining locations and conditions at which markets for such systems could be developed. The results suggest that small geothermal systems offer substantial economic and environmental advantages for powering off-grid towns and villages. Geothermal power is most likely to be economic if the system size is 300 kW or greater, down to reservoir temperatures of 100{degree}C. For system sizes smaller than 300 kW, the economics can be favorable if the reservoir temperature is about 120{degree}C or above. Important markets include sites remote from grids in many developing and developed countries. Estimates of geothermal resources in many developing countries are shown.

Entingh, Daniel J.; Easwaran, Eyob.; McLarty, Lynn

1994-08-08

34

Radionuclide mobility in the shallow portion of an active high-temperature geothermal system  

SciTech Connect

Accurate knowledge of the behavior of radionuclides in natural rock-water systems is crucial for the prediction of the consequences of failure of a high-level nuclear waste repository. Work in progress at Argonne National Laboratory involves the detailed geochemical analysis of rock, mineral, and water samples from shallow drill holes in a thermal area of Yellowstone National Park. This study is designed to provide data that will increase our understanding of the behavior of a group of radionuclides in an environment similar to that of the near field of a high-level nuclear waste repository.

Sturchio, N.C.; Seitz, M.G.

1984-01-01

35

New and different geothermal drilling fluids system  

SciTech Connect

The traditional geothermal drilling fluid in Southern California has consisted of sepiolite clay as a viscosifier and a large quantity of lignite as a filtration control agent. Occidental Geothermal Inc., has tried and successfully tested an alternative mud system for Geothermal drilling. Its main components are IML-TEMP additive for high temperature rheological control and either CHEMTROL-X additive or DFE 104 for filtration control. The use of Wyoming bentonite, often avoided because of its tendency to gel excessively at high temperatures, can and should be used in this mud system to promote better wall cake characteristics and filtration control. An examination is made of Occidential's Rutherford No. 1 well in the East Brawley area of Southern California, a geothermal well that successfully used this alternative mud system.

Conners, J.H. II; Otto, M.J.

1980-09-01

36

The Geothermal Field Camp: Capacity building for geothermal energy systems in Indonesia  

NASA Astrophysics Data System (ADS)

In July 2011, the first geothermal field camp was hold on Java/Indonesia near the city Bandung south of the volcanic field Tangkuban Perahu. The course was organized by the Institut Teknologie Bandung (ITB) and International Centre for Geothermal Research (ICGR) of the German Centre of Geosciences (GFZ). The purpose of the Geothermal Field Camp is to combine both field based work and laboratory analysis to ultimately better understand the data collected in field and to integrate data gained by various disciplines. The training belongs to a capacity building program for geothermal energy systems in Indonesia and initially aims to train the trainers. In a later stage, the educational personal trained by the Geothermal Field Camp shall be able to hold their individual Geothermal Field Camp. This is of special interest for Indonesia where the multitude of islands hindered a broad uniform education in geothermal energy systems. However, Indonesia hold the largest geothermal potential worldwide and educated personal is necessary to successfully develop this huge potential scattered over region in future. The interdisciplinary and integrative approach combined with field based and laboratory methodologies is the guiding principle of the Geothermal Field Camp. Tangkuban Perahu was selected because this field allows the integration of field based structural geological analysis, observation and sampling of geothermal manifestations as hot springs and sinters and ultimately of structural geology and surface geochemistry. This innovative training introduces in methods used in exploration geology to study both, fault and fracture systems and fluid chemistry to better understand the selective fluid flow along certain fractures and faults. Field geology covered the systematic measurement of faults and fractures, fault plane and fracture population analysis. In addition, field hydro-geochemistry focused on sampling techniques and field measurements onsite. Subsequent data analysis of the collected data with statistical techniques allowed a reliable interpretation and application of the related software. The course starts with a lecture day reviewing on geothermal exploration, introduction into structural geology, geochemistry and applied volcanology (1st day) and continues with practical work in the Tangkuban Perahu volcano field and surrounding area (2nd - 5th days, from morning until late afternoon). The collected field data are processed and analyzed daily after field work. On the last day, each group of participants gives a presentation related to their field and laboratory investigations and to evidence the lessons learned. In particular, the participants learn practical work in field and laboratory, and theoretical data analysis. Sampling and analysis of self-collected data are fundamental for any interpretation and assessment of reservoir potential. The success of the first Geothermal Field Camp 2011 speaks for a continuation and extension of the training program in 2012 and the following years. Future activity will integrate more collaboration partners and will cover a larger diversity of educational topics and geological-geothermal setting.

Moeck, I.; Sule, R.; Saptadji, N. M.; Deon, F.; Herdianita, N. R.; Jolie, E.; Suryantini, N.; Erbas, K.

2012-04-01

37

Performance of deep geothermal energy systems  

NASA Astrophysics Data System (ADS)

Geothermal energy is an important source of clean and renewable energy. This project deals with the study of deep geothermal power plants for the generation of electricity. The design involves the extraction of heat from the Earth and its conversion into electricity. This is performed by allowing fluid deep into the Earth where it gets heated due to the surrounding rock. The fluid gets vaporized and returns to the surface in a heat pipe. Finally, the energy of the fluid is converted into electricity using turbine or organic rankine cycle (ORC). The main feature of the system is the employment of side channels to increase the amount of thermal energy extracted. A finite difference computer model is developed to solve the heat transport equation. The numerical model was employed to evaluate the performance of the design. The major goal was to optimize the output power as a function of parameters such as thermal diffusivity of the rock, depth of the main well, number and length of lateral channels. The sustainable lifetime of the system for a target output power of 2 MW has been calculated for deep geothermal systems with drilling depths of 8000 and 10000 meters, and a financial analysis has been performed to evaluate the economic feasibility of the system for a practical range of geothermal parameters. Results show promising an outlook for deep geothermal systems for practical applications.

Manikonda, Nikhil

38

High temperature geothermal energy system  

Microsoft Academic Search

A description is given of a method and apparatus for controlling a well providing access to an underground source of high temperature geothermal brine against flashing as the hot brine is delivered upwardly through the well to surface power apparatus. Plugging of the well by precipitated mineral deposits, as well as other operational problems, are thereby eliminated. A pump down

B. C. McCabe; E. Zajac

1977-01-01

39

Exploration of geothermal systems using hyperspectral thermal infrared remote sensing  

NASA Astrophysics Data System (ADS)

Visible near infrared (VNIR), short-wave infrared (SWIR), and thermal infrared (TIR) remote sensing has long been used for geothermal exploration. Specific focus on the TIR region (8-12 ?m) has resulted in major-rock-forming mineral classes being identified and their areal percentages to be more easily mapped due in part to the linear mixing behavior of TIR emission. To understand the mineral compositional and thermal distribution of active geothermal surfaces systems, hyperspectral TIR data from the Spatially Enhanced Broadband Array Spectrograph System (SEBASS) airborne sensor were acquired over the Salton Sea, CA geothermal fields by The Aerospace Corporation on March 26, 2009 and April 6, 2010. SEBASS collects 128 wavelength channels at ~ 1 m spatial resolution. Such high resolution data are rarely available for this type of scientific analysis and enabled the identification of rare mineral assemblages associated with the geothermally-active areas. One surface unit with a unique spectrum, believed to be a magnesium sulfate of unknown hydration state, was identified for the first time in the SEBASS data. The abundance and distribution of this mineral varied between 2009 and 2010 likely due to the precipitation conditions. Data obtained by the SEBASS sensor were also regressed to the 32 channel spectral resolution of the Mineral and Gas Identifier (MAGI) airborne sensor in order to test sensitivity limits. At this lower spectral resolution, all surface minerals were still effectively identified and therefore validated data at MAGI resolution are still very effective for accurate surface compositional mapping. A similar approach used at active geothermal areas in other semi-arid regions around the world has the potential to better characterize transient mineralogy, identify "indicators minerals", understand the influence of surface and ground water, and ultimately to locate new geothermal targets for future exploration. Furthermore, new Mineral and Gas Identification (MAGI) data serve as an excellent precursor for future spaceborne TIR data such as the system proposed for the Hyperspectral Infrared Imager (HyspIRI) instrument.

Reath, Kevin A.; Ramsey, Michael S.

2013-09-01

40

The interplay between fault-fracture networks activity, fluid flow and mineralization in the Andes: A case study in the Tolhuaca geothermal system, southern Chile  

NASA Astrophysics Data System (ADS)

The nature of the interplay between active tectonics and fluid flow is a key feature to better understand the chemical evolution of fluids in geothermal and hydrothermal systems. The prominent hydrothermal, tectonic and volcanic activity of the Southern Andes volcanic zone (SVZ) makes it one of the best natural laboratories to address this issue. In the northern termination of the Liquiñe-Ofqui Fault System (LOFS), tectonic and volcanic processes interact to define the geothermal field of Tolhuaca. The objective of our current research is to assess the nature of the interplay between brittle deformation and chemical evolution of fluids and mineral paragenesis. Tol-1 is a vertical 1.080 m deep borehole which could yield relevant information regarding the evolution of the Tolhuaca geothermal system. The methodology to achieve our objective includes the structural and geochemical analysis of oriented faults, fault-veins and veins -former pathways- in the core. Structural mapping at the regional scale will help to identify the main structural system, which accommodates the regional stresses, and promotes fluid migration, accumulation and arrest. Fluid inclusions analysis by microthermometry, LA-ICP-MS and Raman spectroscopy will allow a better understanding of the feedback between the fluid flow episodes and the mineralization. More than 120 structural measurements of faults, veins and fault-veins were performed (strike, dip, rake -when available-). Forty seven samples were taken for thin & fluid inclusions sections. Detailed mapping of structures including dip and kinematic indicators from mineral sealing was synthesized in a structural log of Tol-1 core. Our preliminary results show that there is a strong correlation between abundance of structures and rock type. Lava intervals exhibit more intense fracturing and veining than tuff and volcaniclastic intervals. In the upper 300 m of the core, structures are primarily steeply dipping with a dominant normal sense of displacement (some dextral component). Below a cataclastic zone at 300 m, structures are more variable in dip and sense of motion, with some reverse faults. Fluid inclusions petrography reveals the periodically feedback between fault-fractures networks activation and mineral mineralization sealing the conduits for fluid flow.

Sanchez, P.; Perez-Flores, P.; Reich, M.; Arancibia, G.; Cembrano, J. M.

2013-05-01

41

Power conversion and systems for recovering geothermal heat  

Microsoft Academic Search

A process for the conversion of geothermal heat energy into electrical power by advantageously combining direct and indirect heat exchange systems and other systems to maximize the power production is presented. Specifically, a process and system is presented for the utilization of geothermal heat from flashed geothermal hot fluids composed of hot liquid and vapor. The heat from the hot

Sheinbaum

1978-01-01

42

Use of U and Th Decay-Series Disequilibrium to Characterize Geothermal Systems: An Example from the Coso Geothermal System  

Microsoft Academic Search

Uranium and thorium decay series isotopes were measured in fluids and solids in the Coso geothermal system to assess the utility and constrain the limitations of the radioisotopic approach to the investigation of rock-water interaction. Fluid radioisotope measurements indicate substantial kilometer-scale variability in chemistry. Between 1988 and 1990, radium isotope activity ratios indicate temporal variability, which is exhibited by apparent

B. W. Leslie; D. Hammond

2007-01-01

43

A Geothermal GIS for Nevada: Defining Regional Controls and Favorable Exploration Terrains for Extensional Geothermal Systems  

USGS Publications Warehouse

Spatial analysis with a GIS was used to evaluate geothermal systems in Nevada using digital maps of geology, heat flow, young faults, young volcanism, depth to groundwater, groundwater geochemistry, earthquakes, and gravity. High-temperature (>160??C) extensional geothermal systems are preferentially associated with northeast-striking late Pleistocene and younger faults, caused by crustal extension, which in most of Nevada is currently oriented northwesterly (as measured by GPS). The distribution of sparse young (160??C) geothermal systems in Nevada are more likely to occur in areas where the groundwater table is shallow (<30m). Undiscovered geothermal systems may occur where groundwater levels are deeper and hot springs do not issue at the surface. A logistic regression exploration model was developed for geothermal systems, using young faults, young volcanics, positive gravity anomalies, and earthquakes to predict areas where deeper groundwater tables are most likely to conceal geothermal systems.

Coolbaugh, M. F.; Taranik, J. V.; Raines, G. L.; Shevenell, L. A.; Sawatzky, D. L.; Bedell, R.; Minor, T. B.

2002-01-01

44

Convective heat transport in geothermal systems  

SciTech Connect

Most geothermal systems under exploitation for direct use or electrical power production are of the hydrothermal type, where heat is transferred essentially by convection in the reservoir, conduction being secondary. In geothermal systems, buoyancy effects are generally important, but often the fluid and heat flow patterns are largely controlled by geologic features (e.g., faults, fractures, continuity of layers) and location of recharge and discharge zones. During exploitation, these flow patterns can drastically change in response to pressure and temperature declines, and changes in recharge/discharge patterns. Convective circulation models of several geothermal systems, before and after start of fluid production, are described, with emphasis on different characteristics of the systems and the effects of exploitation on their evolution. Convective heat transport in geothermal fields is discussed, taking into consideration (1) major geologic features; (2) temperature-dependent rock and fluid properties; (3) fracture- versus porous-medium characteristics; (4) single- versus two-phase reservoir systems; and (5) the presence of noncondensible gases.

Lippmann, M.J.; Bodvarsson, G.S.

1986-08-01

45

Induced seismicity associated with enhanced geothermal system  

SciTech Connect

Enhanced Geothermal Systems (EGS) offer the potential to significantly add to the world energy inventory. As with any development of new technology, some aspects of the technology has been accepted by the general public, but some have not yet been accepted and await further clarification before such acceptance is possible. One of the issues associated with EGS is the role of microseismicity during the creation of the underground reservoir and the subsequent extraction of the energy. The primary objectives of this white paper are to present an up-to-date review of the state of knowledge about induced seismicity during the creation and operation of enhanced geothermal systems, and to point out the gaps in knowledge that if addressed will allow an improved understanding of the mechanisms generating the events as well as serve as a basis to develop successful protocols for monitoring and addressing community issues associated with such induced seismicity. The information was collected though literature searches as well as convening three workshops to gather information from a wide audience. Although microseismicity has been associated with the development of production and injection operations in a variety of geothermal regions, there have been no or few adverse physical effects on the operations or on surrounding communities. Still, there is public concern over the possible amount and magnitude of the seismicity associated with current and future EGS operations. It is pointed out that microseismicity has been successfully dealt with in a variety of non-geothermal as well as geothermal environments. Several case histories are also presented to illustrate a variety of technical and public acceptance issues. It is concluded that EGS Induced seismicity need not pose any threat to the development of geothermal resources if community issues are properly handled. In fact, induced seismicity provides benefits because it can be used as a monitoring tool to understand the effectiveness of the EGS operations and shed light on the mechanics of the reservoir.

Majer, Ernest; Majer, Ernest L.; Baria, Roy; Stark, Mitch; Oates, Stephen; Bommer, Julian; Smith, Bill; Asanuma, Hiroshi

2006-09-26

46

Power producing system employing geothermally heated fluid  

Microsoft Academic Search

A power producing system includes a source of geothermally heated fluid having inorganic salts dissolved therein. The fluid is directed through a first direct contact heat exchanger in heat transfer relation with a working fluid of a type insoluble in a liquid including inorganic salts. The vaporous working fluid thus produced is expanded through a prime mover and then directed

Shields

1977-01-01

47

Use of U and Th Decay-Series Disequilibrium to Characterize Geothermal Systems: An Example from the Coso Geothermal System  

NASA Astrophysics Data System (ADS)

Uranium and thorium decay series isotopes were measured in fluids and solids in the Coso geothermal system to assess the utility and constrain the limitations of the radioisotopic approach to the investigation of rock-water interaction. Fluid radioisotope measurements indicate substantial kilometer-scale variability in chemistry. Between 1988 and 1990, radium isotope activity ratios indicate temporal variability, which is exhibited by apparent mixing relationships observed as a function of time for single wells. Activity ratios of Ra-224/Ra-226 and Ra- 228/Ra-226, and the processes that contribute and remove these radionuclide to and from the fluids, constrain residence times of fluids and may help constrain fluid velocities in the geothermal system. Activity ratios of Ra- 224/Ra-226 > ten were measured. In groundwater and geothermal systems ratios of Ra-224/Ra-226 > ten are limited to zones of thermal upwelling or very young (days to weeks) waters in mountainous areas. Rn-222 results indicate that radon is also an effective tracer for steam velocities within the geothermal system. Analysis of carbon dioxide and Rn-222 data indicates that the residence time of steam (time since separation from the liquid) is short (probably less than four days). Estimates of fluid velocities derived from Rn-222 and radium isotopic measurements are within an order of magnitude of velocities derived from a fluorescein tracer test. Both Rn-222 and Ra-224 activities are higher in single-phase fluids in the northwest as compared to the southeast, indicating a higher rock-surface-area/water-volume ratio in the northwest. Thus, measurements of short-lived radioisotopes and gaseous phase constituents can constrain processes and characteristics of geothermal systems that are usually difficult to constrain (e.g., surface area/volume, residence times). The NRC staff views expressed herein are preliminary and do not constitute a final judgment or determination of the matters addressed or of the acceptability of a license application for a geologic repository at Yucca Mountain.

Leslie, B. W.; Hammond, D.

2007-12-01

48

Materials selection guidelines for geothermal energy utilization systems  

SciTech Connect

This manual includes geothermal fluid chemistry, corrosion test data, and materials operating experience. Systems using geothermal energy in El Salvador, Iceland, Italy, Japan, Mexico, New Zealand, and the United States are described. The manual provides materials selection guidelines for surface equipment of future geothermal energy systems. The key chemical species that are significant in determining corrosiveness of geothermal fluids are identified. The utilization modes of geothermal energy are defined as well as the various physical fluid parameters that affect corrosiveness. Both detailed and summarized results of materials performance tests and applicable operating experiences from forty sites throughout the world are presented. The application of various non-metal materials in geothermal environments are discussed. Included in appendices are: corrosion behavior of specific alloy classes in geothermal fluids, corrosion in seawater desalination plants, worldwide geothermal power production, DOE-sponsored utilization projects, plant availability, relative costs of alloys, and composition of alloys. (MHR)

Ellis, P.F. II; Conover, M.F.

1981-01-01

49

College of Idaho Geothermal System, Caldwell, Idaho  

SciTech Connect

There appears to be a good potential for a 160{sup 0}F resource at the College of Idaho site. Both existing well data and recent geologic and hydrologic investigations suggest that such a temperature should be available at a depth of approximately 3500 feet. Use of a temperature in the 160{sup 0}F range would not permit a 100% displacement of present natural gas use for space and domestic hot water. Because these systems were typically designed for 200{sup 0}F water or low pressure steam (approx. 220{sup 0}F), the performance of the existing equipment would be less than peak building requirements. However, even without major system modifications (the cost of which would be unreasonable), a geothermal system based on the above resource temperature would be capable of displacing about 78% of current natural gas consumption attributable to space and domestic hot water heating. The system outlined in the report would consist of a 3500 foot production well which would supply geothermal fluid to 12 major buildings on campus. Geothermal water would be passed through heat exchangers in each building. The heat exchangers would deliver heat to the existing heating loops. Most buildings would still require a small amount of input from the existing boiler during the coldest periods of the year. After having passed through the system, the geothermal water would then be injected into a disposal well. This is a key factor in the overall economics of the system. The assumption has been made that a full depth (3550 foot) injection well would be required. It is possible, though unclear at this point, that injection could be accomplished at a shallower depth into a similar aquifer. Since the injection well amounts to 24% of the total system capital cost, this is an important factor.

Rafferty, K.

1984-10-01

50

Finite-element solutions for geothermal systems  

NASA Technical Reports Server (NTRS)

Vector potential and scalar potential are used to formulate the governing equations for a single-component and single-phase geothermal system. By assuming an initial temperature field, the fluid velocity can be determined which, in turn, is used to calculate the convective heat transfer. The energy equation is then solved by considering convected heat as a distributed source. Using the resulting temperature to compute new source terms, the final results are obtained by iterations of the procedure. Finite-element methods are proposed for modeling of realistic geothermal systems; the advantages of such methods are discussed. The developed methodology is then applied to a sample problem. Favorable agreement is obtained by comparisons with a previous study.

Chen, J. C.; Conel, J. E.

1977-01-01

51

Forecast of geothermal-drilling activity  

SciTech Connect

The number of geothermal wells that will be drilled to support electric power production in the United States through 2000 A.D. are forecasted. Results of the forecast are presented by 5-year periods for the five most significant geothermal resources.

Mansure, A.J.; Brown, G.L.

1982-07-01

52

The Examination of Afyonkarahisar's Geothermal System Corrosion  

NASA Astrophysics Data System (ADS)

Corrosion and scaling of metal surfaces are the major problems caused by geothermal fluids when metallic structures are used. This article describes a study of corrosion and scaling problems in the Afyonkarahisar Geothermal Heating System (AFJET) in Afyonkarahisar, Turkey. Water analysis, XRD, SEM, EDX, IC, ICP-OES analyses, and electrochemical methods were used in this study. Pentasodium triphosphate (Na5P3O10), maleic anhydride (C4H2O3), and 1,3-benzendisulfonic acid disodium salt (C6H4Na2O6S2) were used as corrosion inhibitors. Tests were carried out using geothermal water from AF11 well. The experimental temperatures were chosen as 298, 333, and 358 K. Inhibitor concentrations were chosen as 1 × 10-1, 1 × 10-2, 1 × 10-3, and 1 × 10-4 mol/dm3. Moreover, mixed inhibitor solutions were prepared using the inhibitor concentrations that showed the best inhibition. The first mixed inhibitor solution showed 96% inhibition. The second mixed inhibitor solution showed 90% inhibition. The tested inhibitors act as anodic inhibitors. XRD analysis shows that there is CaCO3 aragonite scaling in the system. Increasing TDS, alkalinity, and hardness all promote scale formation. The photomicrographs from SEM-EDX and the metallographic microscope show that the tested inhibitors form a protective film on the surface. IC and ICP-OES analyses show that the concentration of Ca2+ is very high, which supports scale formation.

Buyuksagis, A.; Erol, S.

2013-02-01

53

Natural radioactivity levels of geothermal waters and their influence on soil and agricultural activities.  

PubMed

All over the world geothermal sources are used for different purposes. The contents of these waters are important to understand positive/negative effects on human life. In this study, natural radioactivity concentrations of geothermal waters were investigated to evaluate the effect on soils and agricultural activities. Geothermal water samples were collected from the Seferihisar Geothermal Region, and the radon and radium concentrations of these waters were analysed using a collector chamber method. Also soil samples, which are irrigated with geothermal waters, were collected from the surroundings of geothermal areas, and natural radioactivity concentrations of collected samples (U, Th and K) were determined using an NaI(Tl) detector system. The activity concentrations of radon and radium were found to be 0.6-6.0 and 0.1-1.0 Bq l(-1), respectively. Generally, the obtained results are not higher compared with the geothermal waters of the world. The activity concentrations in soils were found to be in the range of 3.3-120.3 Bq kg(-1) for (226)Ra (eU), 0.3-108.5 Bq kg(-1) for (232)Th (eTh), 116.0-850.0 Bq kg(-1) for (40)K (% K). PMID:24026900

Murat Saç, Müslim; Aydemir, Sercan; Içhedef, Mutlu; Kumru, Mehmet N; Bolca, Mustafa; Ozen, Fulsen

2014-01-01

54

Temporary Cementitious Sealers in Enhanced Geothermal Systems  

SciTech Connect

Unlike conventional hydrothennal geothermal technology that utilizes hot water as the energy conversion resources tapped from natural hydrothermal reservoir located at {approx}10 km below the ground surface, Enhanced Geothermal System (EGS) must create a hydrothermal reservoir in a hot rock stratum at temperatures {ge}200 C, present in {approx}5 km deep underground by employing hydraulic fracturing. This is the process of initiating and propagating a fracture as well as opening pre-existing fractures in a rock layer. In this operation, a considerable attention is paid to the pre-existing fractures and pressure-generated ones made in the underground foundation during drilling and logging. These fractures in terms of lost circulation zones often cause the wastage of a substantial amount of the circulated water-based drilling fluid or mud. Thus, such lost circulation zones must be plugged by sealing materials, so that the drilling operation can resume and continue. Next, one important consideration is the fact that the sealers must be disintegrated by highly pressured water to reopen the plugged fractures and to promote the propagation of reopened fractures. In response to this need, the objective of this phase I project in FYs 2009-2011 was to develop temporary cementitious fracture sealing materials possessing self-degradable properties generating when {ge} 200 C-heated scalers came in contact with water. At BNL, we formulated two types of non-Portland cementitious systems using inexpensive industrial by-products with pozzolanic properties, such as granulated blast-furnace slag from the steel industries, and fly ashes from coal-combustion power plants. These byproducts were activated by sodium silicate to initiate their pozzolanic reactions, and to create a cemetitious structure. One developed system was sodium silicate alkali-activated slag/Class C fly ash (AASC); the other was sodium silicate alkali-activated slag/Class F fly ash (AASF) as the binder of temper-try sealers. Two specific additives without sodium silicate as alkaline additive were developed in this project: One additive was the sodium carboxymethyl cellulose (CMC) as self-degradation promoting additive; the other was the hard-burned magnesium oxide (MgO) made from calcinating at 1,000-1,500 C as an expansive additive. The AASC and AASF cementitious sealers made by incorporating an appropriate amount of these additives met the following six criteria: 1) One dry mix component product; 2) plastic viscosity, 20 to 70 cp at 300 rpm; 3) maintenance of pumpability for at least 1 hour at 85 C; 4) compressive strength >2000 psi; 5) self-degradable by injection with water at a certain pressure; and 6) expandable and swelling properties; {ge}0.5% of total volume of the sealer.

Sugama T.; Pyatina, T.; Butcher, T.; Brothers, L.; Bour, D.

2011-12-31

55

Enthalpy restoration in geothermal energy processing system  

DOEpatents

A geothermal deep well energy extraction system is provided of the general type in which solute-bearing hot water is pumped to the earth's surface from a relatively low temperature geothermal source by transferring thermal energy from the hot water to a working fluid for driving a primary turbine-motor and a primary electrical generator at the earth's surface. The superheated expanded exhaust from the primary turbine motor is conducted to a bubble tank where it bubbles through a layer of sub-cooled working fluid that has been condensed. The superheat and latent heat from the expanded exhaust of the turbine transfers thermal energy to the sub-cooled condensate. The desuperheated exhaust is then conducted to the condenser where it is condensed and sub-cooled, whereupon it is conducted back to the bubble tank via a barometric storage tank. The novel condensing process of this invention makes it possible to exploit geothermal sources which might otherwise be non-exploitable.

Matthews, Hugh B. (Boylston, MA)

1983-01-01

56

Geothermal Systems of the Yellowstone Caldera Field Trip Guide  

SciTech Connect

Geothermal studies are proceedings on two fronts in the West Yellowstone area. High-temperature resources for the generation of electricity are being sought in the Island Park area, and lower temperatures resources for direct applications, primarily space heating, are being explored for near the town of West Yellowstone. Potential electric geothermal development in the Island Park area has been the subject of widespread publicity over fears of damage to thermal features in Yellowstone Park. At the time of writing this guide, companies have applied for geothermal leases in the Island Park area, but these leases have not yet been granted by the US Forest Service. The Senate is now discussing a bill that would regulate geothermal development in Island Park; outcome of this debate will determine the course of action on the lease applications. The Island Park area was the site of two cycles of caldera activity, with major eruptions at 2.0 and 1.2 million years ago. The US Geological Survey estimates that 16,850 x 10{sup 18} joules of energy may remain in the system. Geothermal resources suitable for direct applications are being sought in the West Yellowstone vicinity by the Montana Bureau of Mines and Geology, under funding from the US Department of Energy. West Yellowstone has a mean annual temperature of 1-2 C. Research thus far suggests that basement rocks in the vicinity are at a depth of about 600 m and are probably similar to the rocks exposed north of Hebgen Lake, where Precambrian, Paleozoic and Mesozoic rocks have been mapped. A few sites with anomalously warm water have been identified near the town. Work is continuing on this project.

Foley, Duncan; Neilson, Dennis L.; Nichols, Clayton R.

1980-09-08

57

ELVIS: Multi-Electrolyte Aqueous Activity Model for Geothermal Solutions  

NASA Astrophysics Data System (ADS)

High temperature, pressure, and fluid salinities render geochemical modeling of fluid-rock interactions in Enhanced Geothermal Systems a demanding task. Accurate prediction of fluid-mineral equilibria strongly depends on the availability of thermodynamic data and activity models. Typically, the Pitzer activity model is applied for geothermal fluids. A drawback of this model is the large number of parameters required to account for temperature and pressure dependencies, which significantly reduces computational efficiency of reactive transport simulations. In addition, most available parameterizations are valid only at vapor-saturated conditions. As an alternative we implemented the EUNIQUAC local composition model [2] that needs substantially fewer fitting parameters. However, the current EUNIQUAC model design does not include provision for high temperature (>150°C) applications and lacks a formulation for pressure dependence. Therefore, its application to geothermal conditions requires a re-formulation and re-fitting of the model. We developed a new tool termed GEMSFIT that allows generic fitting of activity models (for aqueous electrolyte and non-electrolyte solutions) and equations of state implemented in our geochemical equilibrium solver GEM-Selektor (http://gems.web.psi.ch). GEMSFIT combines a PostgreSQL database for storing and managing the datasets of experimental measurements and interaction parameters, the parallelized genetic algorithm toolbox of MATLAB° for the parameter fitting, and an interface to the numerical kernel of GEM-Selektor to access activity models and perform chemical equilibrium calculations. Benchmarking of the partly re-parameterized EUNIQUAC model against Pitzer revealed that the former is less accurate, which can result in incorrect predictions of mineral precipitation/dissolution. Consequently, we modified the EUNIQUAC model and concurrently introduced a pressure dependence to be able to fit experimental data over wide ranges of pressure, temperature, and composition. The new model, called ELVIS, combines an electrostatic framework developed by Helgeson and coworkers [1] with non- electrostatic concepts derived from the EUNIQUAC model [2]. ELVIS has significantly less fitting parameters than the Pitzer approach, but is sufficiently accurate in predicting mineral solubility within experimental error. Results of first parameterizations of ELVIS to geothermal solutions (dilute to concentrated brines from ambient conditions to ~300°C and ~800bars) will be presented. [1] Helgeson, H. H., Kirkham, D. H., Flowers, G. C. (1981), Am. J. Sc. 281, 1249-1516. [2] Thomsen, K., Rasmussen, P., Gani, R. (1996), Chem. Eng. Sc. 51, 3675-3683.

Hingerl, F. F.; Wagner, T.; Driesner, T.; Kulik, D. A.; Kosakowski, G.

2011-12-01

58

Choosing a Geothermal as an HVAC System.  

ERIC Educational Resources Information Center

Describes the process of selecting and installing geothermal water source heat pumps for new residence halls at Johnson Bible College in Knoxville, Tennessee, including choosing the type of geothermal design, contractors, and interior equipment, and cost and payback. (EV)

Lensenbigler, John D.

2002-01-01

59

GEOTHERMAL ENVIRONMENTAL IMPACT ASSESSMENT: SUBSURFACE ENVIRONMENTAL ASSESSMENT FOR FOUR GEOTHERMAL SYSTEMS  

EPA Science Inventory

This is the second in a series of reports concerning the environmental assessments of effluent extraction, energy conversion, and waste disposal in geothermal systems. This study involves the subsurface environmental impact of the Imperial Valley and The Geysers, California; Klam...

60

A GEOTHERMAL GIS FOR NEVADA: DEFINING REGIONAL CONTROLS AND FAVORABLE EXPLORATION TERRAINS FOR EXTENSIONAL GEOTHERMAL SYSTEMS  

Microsoft Academic Search

Spatial analysis with a GIS was used to evaluate geothermal systems in Nevada using digital maps of geology, heat flow, young faults, young volcanism, depth to groundwater, groundwater geochemistry, earthquakes, and gravity. High-temperature (>160°C) extensional geothermal systems are preferentially associated with northeast-striking late Pleistocene and younger faults, caused by crustal extension, which in most of Nevada is currently oriented northwesterly

Mark F. Coolbaugh; James V. Taranik; Gary L. Raines; Lisa A. Shevenell; Don L. Sawatzky; Richard Bedell; Timothy B. Minor

61

Mantle helium and carbon isotopes in Separation Creek Geothermal Springs, Three Sisters area, Central Oregon: Evidence for renewed volcanic activity or a long term steady state system?  

SciTech Connect

Cold bubbling springs in the Separation Creek area, the locus of current uplift at South Sister volcano show strong mantle signatures in helium and carbon isotopes and CO{sub 2}/{sup 3}He. This suggests the presence of fresh basaltic magma in the volcanic plumbing system. Currently there is no evidence to link this system directly to the uplift, which started in 1998. To the contrary, all geochemical evidence suggests that there is a long-lived geothermal system in the Separation Creek area, which has not significantly changed since the early 1990s. There was no archived helium and carbon data, so a definite conclusion regarding the strong mantle signature observed in these tracers cannot yet be drawn. There is a distinct discrepancy between the yearly magma supply required to explain the current uplift (0.006 km{sup 3}/yr) and that required to explain the discharge of CO{sub 2} from the system (0.0005 km{sup 3}/yr). This discrepancy may imply that the chemical signal associated with the increase in magma supply has not reached the surface yet. With respect to this the small changes observed at upper Mesa Creek require further attention, due to the recent volcanic vent in that area it may be the location were the chemical signal related to the uplift can most quickly reach the surface. Occurrence of such strong mantle signals in cold/diffuse geothermal systems suggests that these systems should not be ignored during volcano monitoring or geothermal evaluation studies. Although the surface-expression of these springs in terms of heat is minimal, the chemistry carries important information concerning the size and nature of the underlying high-temperature system and any changes taking place in it.

van Soest, M.C.; Kennedy, B.M.; Evans, W.C.; Mariner, R.H.

2002-04-30

62

Geothermal activity in Italy: present status and future prospects  

SciTech Connect

In the Italian Peninsula the Apennines separate a relatively cold Po-Adriatic-Ionian ''foredeep'' external belt from a warmer Tyrrhenian ''back-arc'' internal tensional belt. The latter i characterized by high geothermal heat flow together with conspicuous recent or present-day volcani phenomena. In this area, extending from Tuscany to Campania, lie the known steam- and waterdominated fields. Other ''warm'' areas are located on some Tyrrhenian islands. Within the ''cold'' external belt, interesting locations for low enthalpy utilizations can be found in the Po river valley, particularly in the eastern part near Ferrara and Abano. Since 1977 ENEL (National Electri Energy Agency) and AGIP (State Oil Company) have been jointly conducting geothermal activities in Italy, with the exception of the Tuscan geothermal area where ENEL operates on an exclusive basis. At present the areas surveyed cover about 8250 kmS. As of December 1983 the geothermal installed capacity was 456.2 MW (net capacity 340 MW) and low-temperature geothermal resources equivalent to 100,000 OET /yr were being used. The National Energy Plant (PEN), issued on 4 December 1981, forecast for the year 1990 a geothermal power increment of 200 MW /SUB e/ above the 449.1 MW /SUB e/ already installed. The target in the low enthalpy non-electric sector is to save 300,000 OET/yr by 1990. This paper describes the activities carried out from March 1975 to December 1983 and the main projects in progress.

Carella, R.; Palmerini, C.G.; Stefani, G.C.; Verdiani, G.

1985-01-01

63

Application of direct contact heat exchangers in geothermal systems  

Microsoft Academic Search

Two applications of direct-contact heat exchangers (DCHs) used in geothermal systems are examined. The first type of DCH is applied to a binary cycle where a secondary fluid is vaporized in contact with the brine (direct contact evaporator). The second type of DCH is applied to a geothermal power plant operating on water vapor only (direct contact condenser); in this

I. Oliker

1977-01-01

64

Roosevelt Hot Springs geothermal system, Utah - case study  

Microsoft Academic Search

The Roosevelt Hot Springs geothermal system has been undergoing intensive exploration since 1974 and has been used as a natural laboratory for the development and testing of geothermal exploration methods by research organizations. This paper summarizes the geological, geophysical, and geochemistry data which have been collected since 1974, and presents a retrospective strategy describing the most effective means of exploration

H. P. Ross; D. L. Nielson; J. N. Moore

1982-01-01

65

3rd Quarterly technical progress report for geothermal system temperature-depth database  

SciTech Connect

At the Southern Methodist University Geothermal Laboratory in Dallas, Texas, the Earth`s surface and internal temperature are studied. With financial support from the U.S. Department of Energy, a data base containing geothermal temperature well information for the United States is being developed. During this calendar quarter, activity with this project has continued involving several different tasks: planning and development of the geothermal system thermal-well data base and temperature-depth data, and development of a World Wide Web home page.

Blackwell, D.D.

1997-10-31

66

Fluid-inclusion gas composition from an active magmatic-hydrothermal system: a case study of The Geysers, California geothermal field  

SciTech Connect

Hydrothermal alteration and the active vapor-dominated geothermal system at The Geysers, CA are related to a composite hypabyssal granitic pluton emplaced beneath the field 1.1 to 1.2 million years ago. Deep drill holes provide a complete transect across the thermal system and samples of the modem-day steam. The hydrothermal system was liquid-dominated prior to formation of the modem vapor-dominated regime at 0.25 to 0.28 Ma. Maximum temperatures and salinities ranged from 440 C and 44 wt. percent NaCl equivalent in the biotite hornfels adjacent to the pluton to 305 C and 5 wt. percent NaCl equivalent at distances of 1730 m from the intrusive contact. The major, minor, and noble gas compositions of fluid inclusions in the hydrothermally altered rocks were integrated with microthermometric and mineralogic data to determine their sources and the effects of mixing and boiling. Major and minor gaseous species were released from the inclusions by crushing or thermal decrepitation; noble gases were released by crushing. The samples were analyzed by mass spectrometry. The analyses document the presence of magmatic, crustal, and meteoric components in the trapped fluids. Hydrothermal fluids present during the liquid-dominated phase of the system contained gaseous species derived mainly from crustal and magmatic sources. At The Geysers, N-2/Ar ratios greater than 525 and He-3/He-4 ratios of 6-10.7 Ra are diagnostic of a magmatic component. Crustal gas has CO2/CH4 ratios less than 4, N-2/Ar ratios between 45 and 525, and low 3He/4He ratios (0.5 Ra). Meteoric fluids have CO2/CH4 ratios greater than 4 and N2/Ar ratios between 38 (air-saturated water) and 84 (air). However, N-2/Ar ratios between 15 and 110 can result from boiling. Ratios less than 15 reflect the incorporation of N-2 into NH3-bearing clay minerals. In the central Geysers, the incursion of meteoric fluids occurred during the transition from the liquid- to vapor-dominated regime. Variations in the relative CH4, CO2, and H-2 contents of the gas analyses demonstrate that boiling took place under open-system conditions. The gas data indicate that the inclusions have remained closed to the diffusion of He and H-2 since their formation.

Moore, Joseph N.; Norman, David I.; Kennedy, B. Mack.

2001-03-01

67

3D characterization of a Great Basin geothermal system: Astor Pass, NV  

NASA Astrophysics Data System (ADS)

The Great Basin exhibits both anomalously high heat flow (~75±5 mWm-2) and active faulting and extension resulting in robust geothermal activity. There are ~430 known geothermal systems in the Great Basin, with evidence suggesting that undiscovered blind geothermal systems may actually represent the majority of geothermal activity. These systems employ discrete fault intersection/interaction areas as conduits for geothermal circulation. Recent studies show that steeply dipping normal faults with step-overs, fault intersections, accommodation zones, horse-tailing fault terminations and transtensional pull-aparts are the most prominent structural controls of Great Basin geothermal systems. These fault geometries produce sub-vertical zones of high fault and fracture density that act as fluid flow conduits. Structurally controlled fluid flow conduits are further enhanced when critically stressed with respect to the ambient stress conditions. The Astor Pass blind geothermal system, northwestern Nevada, lies along the boundary between the Basin and Range to the east and the Walker Lane to the west. Along this boundary, strain is transferred from dextral shear in the Walker Lane to west-northwest directed extension in the Basin and Range. As such, the Astor Pass area lies in a transtensional setting consisting of both northwest-striking, left-stepping dextral faults and more northerly striking normal faults. The Astor Pass tufa tower implies the presence of a blind geothermal system. Previous studies suggest that deposition of the Astor Pass tufa was controlled by the intersection of a northwest-striking dextral normal fault and north-northwest striking normal fault. Subsequent drilling (to ~1200 m) has revealed fluid temperatures of ~94°C, confirming the presence of a blind geothermal system at Astor Pass. Expanding upon previous work and employing additional detailed geologic mapping, interpretation of 2D seismic reflection data and analysis of well cuttings, a 3-dimensional geologic model of the Astor Pass blind geothermal system was constructed. The 3D structural framework indicates that the Pleistocene tufa is associated with three discrete fault zones whose intersections plunge moderately to steeply NW-NNW. These critically stressed fault intersections act as conduits for upwelling geothermal fluids.

Siler, D. L.; Mayhew, B.; Faulds, J. E.

2012-12-01

68

United Nations geothermal activities in developing countries  

SciTech Connect

The United Nations implements technical cooperation projects in developing countries through its Department of Technical Cooperation for Development (DTCD). The DTCD is mandated to explore for and develop natural resources (water, minerals, and relevant infrastructure) and energy - both conventional and new and renewable energy sources. To date, the United Nations has been involved in over 30 geothermal exploration projects (completed or underway) in 20 developing countries: 8 in Africa (Djibouti, Ethiopia, Kenya, Madagascar); 8 in Asia (China, India, Jordan, Philippines, Thailand); 9 in Latin America (Bolivia, Chile, El Salvador, Honduras, Mexico, Nicaragua, Panama) and 6 in Europe (Greece, Romania, Turkey, Yugoslavia). Today, the DTCD has seven UNDP geothermal projects in 6 developing countries. Four of these (Bolivia, China, Honduras, and Kenya) are major exploration projects whose formulation and execution has been possible thanks to the generous contributions under cost-sharing arrangements from the government of Italy. These four projects are summarized.

Beredjick, N.

1987-07-01

69

Evaluation of Geothermal Heat Pump Systems under Various Conditions  

NASA Astrophysics Data System (ADS)

Experimental and numerical test were accomplished to evaluate the relations between the geothermal system and the hydrogeological condition. Sand tank experiment was designed. Combinations of different gradients and temperature gradients were applied for testing the real-time monitoring performance. Numerical modeling results were compared with the experimental data. Water injection-system imitating open- and closed-loop geothermal heat pumps were applied to estimate the change of the distribution of ambient groundwater temperature. The experimental results of different settings were used to estimate the effects of shallow depth geothermal energy utilization on the groundwater system.

Lee, S.; Bae, G.; Lee, K.

2006-12-01

70

Geothermal Energy.  

National Technical Information Service (NTIS)

The discussions cover six areas of geothermal resource utilization: (1) concept and potential of the resource; (2) natural geothermal systems; (3) artifically stimulated, dry hot rock geothermal systems; (4) energy utilization alternatives; (5) power cycl...

J. W. Tester S. L. Milora

1975-01-01

71

Double-diffusive convection in geothermal systems: the salton sea, California, geothermal system as a likely candidate  

USGS Publications Warehouse

Much has been published about double-diffusive convection as a mechanism for explaining variations in composition and temperature within all-liquid natural systems. However, relatively little is known about the applicability of this phenomenon within the heterogeneous rocks of currently active geothermal systems where primary porosity may control fluid flow in some places and fractures may control it in others. The main appeal of double-diffusive convection within hydrothermal systems is-that it is a mechanism that may allow efficient transfer of heat mainly by convection, while at the same time maintaining vertical and lateral salinity gradients. The Salton Sea geothermal system exhibits the following reservoir characteristics: (1) decreasing salinity and temperature from bottom to top and center toward the sides, (2) a very high heat flow from the top of the system that seems to require a major component of convective transfer of heat within the chemically stratified main reservoir, and (3) a relatively uniform density of the reservoir fluid throughout the system at all combinations of subsurface temperature, pressure, and salinity. Double-diffusive convection can account for these characteristics very nicely whereas other previously suggested models appear to account either for the thermal structure or for the salinity variations, but not both. Hydrologists, reservoir engineers, and particularly geochemists should consider the possibility and consequences of double-diffusive convection when formulating models of hydrothermal processes, and of the response of reservoirs to testing and production. ?? 1990.

Fournier, R. O.

1990-01-01

72

Geothermal wells: a forecast of drilling activity  

SciTech Connect

Numbers and problems for geothermal wells expected to be drilled in the United States between 1981 and 2000 AD are forecasted. The 3800 wells forecasted for major electric power projects (totaling 6 GWe of capacity) are categorized by type (production, etc.), and by location (The Geysers, etc.). 6000 wells are forecasted for direct heat projects (totaling 0.02 Quads per year). Equations are developed for forecasting the number of wells, and data is presented. Drilling and completion problems in The Geysers, The Imperial Valley, Roosevelt Hot Springs, the Valles Caldera, northern Nevada, Klamath Falls, Reno, Alaska, and Pagosa Springs are discussed. Likely areas for near term direct heat projects are identified.

Brown, G.L.; Mansure, A.J.; Miewald, J.N.

1981-07-01

73

Investigation of Induced Seismicity from a Geothermal System, Neal Hot Springs, Eastern Oregon  

NASA Astrophysics Data System (ADS)

Newly acquired geophysical data from an eleven-seismometer network surrounding the Neal Hot Springs (NHS) Geothermal Power Plant in eastern Oregon was analyzed for induced seismicity and geothermal fluid flow. Major faults associated with the Oregon-Idaho Graben and the western Snake River Plain provides pathways for deep geothermal fluid flow for the NHS hot-water system. Our short-period seismic stations, can detect regional events not in published earthquake catalogs. These stations have been collecting seismic data from the initiation of the geothermal system's development through fluid injection tests this past summer. Background seismic values were acquired before plant production to measure natural geothermal fluid activity, but no natural fluid flow seismicity was identified. Two local events located less than 10 km to the northeast of NHS along with a catalogued, 2.8 M regional event 200 km away were identified in the data set, verifying the sensitivity and capability of the passive seismic network to capture events that were to occur at NHS. We monitored seismic activity from production and development with 4-8 hour durations for the past 15 months. We identify repeated signals at approximately 2 Hz that likely represent fluid injection or drilling cycles. However, induced earthquakes were not identified during production activities. The lack of microseismic events could be the result of the shallow depth of the geothermal resource, approximately 850 m below the earth surface. Future studies include a receiver function analysis to determine crustal boundaries beneath NHS, along with further monitoring of induced seismicity due to geothermal fluid flow as the geothermal power plant comes online.

Brenn, G. R.; Liberty, L. M.; Van Wijk, K.; Shaltry, D.; Colwell, C.

2012-12-01

74

Evaluation of Geothermal Heat Pump Systems under Various Conditions  

Microsoft Academic Search

Experimental and numerical test were accomplished to evaluate the relations between the geothermal system and the hydrogeological condition. Sand tank experiment was designed. Combinations of different gradients and temperature gradients were applied for testing the real-time monitoring performance. Numerical modeling results were compared with the experimental data. Water injection-system imitating open- and closed-loop geothermal heat pumps were applied to estimate

S. Lee; G. Bae; K. Lee

2006-01-01

75

Active Volcanoes and Their Relation to Geothermal Energy.  

National Technical Information Service (NTIS)

By the use of slides depicting active volcanism, particularly that of Cerro Negro in Nicaragua, an attempt is made to illustrate that volcanism is the result of endogenic process which can be exploited as geothermal energy. (ERA citation 03:044569)

J. G. Viramonte

1976-01-01

76

Engineered geothermal power systems for Singapore  

Microsoft Academic Search

Singapore has a high geothermal gradient (?35°C\\/km) as evidenced by hot springs (70°C) and high heat flow (estimated to be about 130 mW\\/m). In this study, ground water models are presented based on AUTOUGH–2 computer modelling. The models show a freshwater lens up to 4.8 km depth under Singapore's land area, whose temperature increases with depth up to 192°C. Three geothermal

G. J. H. Oliver; A. C. Palmer; H. Tjiawi; F. Zulkefli

2011-01-01

77

Technical support for geopressured-geothermal well activities in Louisiana  

SciTech Connect

Continuous recording microearthquake monitoring networks have been established around US Department of Energy (DOE) geopressured-geothermal design wells in southwestern Louisiana and southeastern Texas since summer 1980 to assess the effects well development may have had on subsidence and growth-fault activation. This monitoring has shown several unusual characteristics of Gulf Coast seismic activity. The observed activity is classified into two dominant types, one with identifiable body phases (type 1) and the other with only surface-wave signatures (type 2). During this reporting period no type 1 or body-wave events were reported. A total of 230 type 2 or surface-wave events were recorded. Origins of the type 2 events are still not positively understood; however, little or no evidence is available to connect them with geopressured-geothermal well activity. We continue to suspect sonic booms from military aircraft or some other human-induced source. 37 refs., 16 figs., 6 tabs.

Not Available

1991-07-01

78

Passive Seismic Monitoring of Mine-scale Geothermal Activity: A Trial at Lihir Open Pit Mine  

NASA Astrophysics Data System (ADS)

The Lihir open pit mine in Papua New Guinea is located inside an old volcano where geothermal activity is strongly present. Outbursts of hot water and steam into the mining areas were a major safety concern. Passive seismic monitoring was carried out at the mine to investigate whether the geothermal activities could be detected and located using microseismic techniques in a mining environment. In this trial, sixteen triaxial geophones which can withstand temperature up to 200°C were used and installed in four deep boreholes inside the pit. The microseismic events were discriminated using the STA/LTA triggering criterion. During 6 weeks of monitoring, more than 17,000 events were recorded. Approximately 12% of the events showed harmonic vibration characteristics similar to those observed in other geothermal and volcanic areas, suggesting that the geothermal activity inside the pit was captured by the microseismic monitoring system. More than 75% of the events present both P and S waves and they were interpreted to be associated with rock fracturing due to stress release near the bottom of the pit. Many geothermal-type events were located in areas where shear events occurred, implying that the detected geothermal events were not far from the mining area below the pit and they may also be associated with mining. The borehole installation of the geophones significantly reduced the interference of mining noise and achieved good observation of the seismic events. However, equipment installation requires great attention as the geophones may be destroyed due to unexpected rising temperature within the boreholes.

Luo, X.; Creighton, A.; Gough, J.

2010-02-01

79

The Newcastle geothermal system, Iron County, Utah  

SciTech Connect

Geological, geophysical and geochemical studies contributed to conceptual hydrologic model of the blind'' (no surface expression), moderate-temperature (greater than 130{degree}C) Newcastle geothermal system, located in the Basin and Range-Colorado Plateau transition zone of southwestern Utah. Temperature gradient measurements define a thermal anomaly centered near the surface trace of the range-bounding Antelope Range fault with and elongate dissipative plume extending north into the adjacent Escalante Valley. Spontaneous potential and resistivity surveys sharply define the geometry of the dominant upflow zone (not yet explored), indicating that most of the thermal fluid issues form a short segment along the Antelope Range fault and discharges into a gently-dipping aquifer. Production wells show that this aquifer lies at a depth between 85 and 95 meter. Electrical surveys also show that some leakage of thermal fluid occurs over a 1.5 km (minimum) interval along the trace of the Antelope Range fault. Major element, oxygen and hydrogen isotopic analyses of water samples indicate that the thermal fluid is a mixture of meteoric water derived from recharge areas in the Pine Valley Mountains and cold, shallow groundwater. A northwest-southeast trending system of faults, encompassing a zone of increased fracture permeability, collects meteoric water from the recharge area, allows circulation to a depth of 3 to 5 kilometers, and intersects the northeast-striking Antelope Range fault. We postulate that mineral precipitates form a seal along the Antelope Range fault, preventing the discharge of thermal fluids into basin-fill sediments at depth, and allowing heated fluid to approach the surface. Eventually, continued mineral deposition could result in the development of hot springs at the ground surface.

Blackett, R.E.; Shubat, M.A.; Bishop, C.E. (Utah Geological and Mineral Survey, Salt Lake City, UT (USA)); Chapman, D.S.; Forster, C.B.; Schlinger, C.M. (Utah Univ., Salt Lake City, UT (USA). Dept. of Geology and Geophysics)

1990-03-01

80

Seismic Activity at tres Virgenes Volcanic and Geothermal Field  

NASA Astrophysics Data System (ADS)

The volcanic and geothermal field Tres Virgenes is in the NE portion of Baja California Sur State, Mexico, between -112°20'and -112°40' longitudes, and 27°25' to 27°36' latitudes. Since 2003 Power Federal Commission and the Engineering Institute of the National Autonomous University of Mexico (UNAM) initiated a seismic monitoring program. The seismograph network installed inside and around the geothermal field consisted, at the beginning, of Kinemetrics K2 accelerometers; since 2009 the network is composed by Guralp CMG-6TD broadband seismometers. The seismic data used in this study covered the period from September 2003 - November 2011. We relocated 118 earthquakes with epicenter in the zone of study recorded in most of the seismic stations. The events analysed have shallow depths (?10 km), coda Magnitude Mc?2.4, with epicentral and hypocentral location errors <2 km. These events concentrated mainly below Tres Virgenes volcanoes, and the geothermal explotation zone where there is a system NW-SE, N-S and W-E of extensional faults. Also we obtained focal mechanisms for 38 events using the Focmec, Hash, and FPFIT methods. The results show normal mechanisms which correlate with La Virgen, El Azufre, El Cimarron and Bonfil fault systems, whereas inverse and strike-slip solutions correlate with Las Viboras fault. Additionally, the Qc value was obtained for 118 events. This value was calculated using the Single Back Scattering model, taking the coda-waves train with window lengths of 5 sec. Seismograms were filtered at 4 frequency bands centered at 2, 4, 8 and 16 Hz respectively. The estimates of Qc vary from 62 at 2 Hz, up to 220 at 16 Hz. The frequency-Qc relationship obtained is Qc=40±2f(0.62±0.02), representing the average attenuation characteristics of seismic waves at Tres Virgenes volcanic and geothermal field. This value correlated with those observed at other geothermal and volcanic fields.

Antayhua, Y. T.; Lermo, J.; Quintanar, L.; Campos-Enriquez, J. O.

2013-05-01

81

Occurence of ore metals in some terrestrial geothermal systems  

SciTech Connect

Drilling programs and the study of active geothermal systems have shown that the reservoir rocks in many fields contain minor quantities of base and precious metals. Commonly, base-metal sulfides occur in the subsurface but, where present, Au, Ag, Hg, As, Tl and Sb rich precipitates deposit near, or at, the surface. Although in some fields (Geysers, Larderello, Tongonan) some of the ore minerals (and others) are relict, there is evidence that they are now depositing in a few systems. Recent work on active hydrothermal systems in New Zealand shows that: (1) Sphalerite, galena, chalcopyrite (forming veins and disseminated discrete crystals) plus rare pentlandite, cobaltite and arsenopyrite, occur at Broadlands, NZ. Rare quantities of base-metal sulfides also occur in cores and cuttings from the geothermal fields of Waiotapu, Kawerau, Tauhara, and Ngawha. Further, Kakimoto (1983) has identified cassiterite, native silver, and trace gold in cores from Tauhara, in the south-eastern part of the Wairakei field. Bore temperatures at the depths from which these minerals were recovered are mostly between 220/sup 0/ and 300/sup 0/C, but at Broadlands are locally as low as 120/sup 0/C. The host rocks are Quaternary calc-alkali, silicic lavas and pyroclastic rocks, andesites, dacite and deep Mesozoic greywackes and argillites; however, there is no obvious relationship between mineralization and stratigraphy, permeability or well output. The deposition of amorphous precious metal precipitates (Au, Ag, Hg, As, Sb, Tl) from hot springs and well discharges has taken place at Broadlands, Waiotapu and Rotokawa; it also occurs at Kawerau. Water discharging from Frying Pan Lake, Waimangu, is presently depositing siliceous sinter containing up to 4.1% tungsten.

Browne, P.

1984-02-01

82

Geothermal direct applications hardware systems development and testing. 1979 summary report  

SciTech Connect

Activities performed during calendar year 1979 for the hardware system development and testing task are presented. The fluidized bed technology was applied to the drying of potato by-products and to the exchange of heat to air in the space heating experiment. Geothermal water was flashed to steam and also used as the prime energy source in the steam distillation of peppermint oil. Geothermal water temperatures as low as 112.8/sup 0/C were utilized to distill alcohol from sugar beet juice, and lower temperature water provided air conditioning through an absorption air conditioning system. These experiments are discussed.

Keller, J.G.

1980-03-01

83

Marketing the Klamath Falls Geothermal District Heating system  

Microsoft Academic Search

The Klamath Falls Geothermal District Heating system was completed in 1981 and, until 1992, there was no formal marketing plan for the system. This lack of marketing and the system history of poor availability combined to reduce or eliminate interest in connecting on the part of local building owners and it served only the original 14 government buildings connected at

Rafferty

1993-01-01

84

Three dimensional images of geothermal systems: local earthquake P-wave velocity tomography at the Hengill and Krafla geothermal areas, Iceland, and The Geysers, California  

USGS Publications Warehouse

Local earthquake tomography - the use of earthquake signals to form a 3-dimensional structural image - is now a mature geophysical analysis method, particularly suited to the study of geothermal reservoirs, which are often seismically active and severely laterally inhomogeneous. Studies have been conducted of the Hengill (Iceland), Krafla (Iceland) and The Geysers (California) geothermal areas. All three systems are exploited for electricity and/or heat production, and all are highly seismically active. Tomographic studies of volumes a few km in dimension were conducted for each area using the method of Thurber (1983).

Julian, B. R.; Prisk, A.; Foulger, G. R.; Evans, J. R.

1993-01-01

85

Community Geothermal Technology Program: Bottom heating system using geothermal power for propagation. Final report, Phases 1 and 2  

Microsoft Academic Search

The objective is to develop and study a bottom-heating system in a greenhouse utilizing geothermal energy to aid germination and speed growth of palms. Source of heat was geothermal brine from HGP-A well. The project was successful; the heat made a dramatic difference with certain varieties, such as Areca catechu (betelnut) with 82% germination with heat, zero without. For other

1990-01-01

86

A chlorite solid solution geothermometer the Los Azufres (Mexico) geothermal system  

Microsoft Academic Search

Chlorite constitutes a major hydrothermal alteration product of metamorphism of andesites, in the active geothermal system of Los Azufres (Mexico). Electron microprobe analyses performed on a set of crystals from each sample show wide variations in composition. Correlation coefficients among chemical constituents were calculated. It is shown that the tetrahedral charge is positively correlated with the octahedral vacancy and negatively

Michel Cathelineau; David Nieva

1985-01-01

87

Geobotanical characterization of a geothermal system using hyperspectral imagery: Long Valley Caldera, CA  

Microsoft Academic Search

We have analyzed hyperspectral Airborne Visible-Infrared Imaging System (AVIRIS) imagery taken in September of 1992 in Long Valley Caldera, CA, a geothermally active region expressed surficially by hot springs and fumaroles. Geological and vegetation mapping are attempted through spectral classification of imagery. Particular hot spring areas in the caldera are targeted for analysis. The data is analyzed for unique geobotanical

M R Carter; S A Cochran; B A Martini; W L Pickles; D C Potts; R E Priest; E A Silver; B A Wayne; W T White

1998-01-01

88

Geomechanics of Hydraulic Stimulation in Geothermal Systems: Designing and Implementing a Successful Enhanced Geothermal System at Desert Peak, Nevada  

NASA Astrophysics Data System (ADS)

Creation of an Enhanced Geothermal System (EGS) in hot but low-permeability rocks involves hydraulic stimulation of fracture permeability to develop a complex heat exchange system with low hydraulic impedance. An integrated study of stress, fractures and rock mechanical properties was conducted to develop the geomechanical framework for a multi-stage EGS stimulation in Desert Peak well 27-15, located at the low-permeability margins of an active geothermal field. The stimulation targeted silicified tuffs and metamorphosed mudstones at depths of 0.9 to 1.8 km and temperatures ~180 to 210° C. Drilling-induced tensile fractures in image logs from well 27-15 show that the least horizontal principal stress (Shmin) is consistent with normal faulting on ESE- and WNW-dipping fractures mapped at the surface and seen in the image logs. A hydraulic fracturing stress measurement indicates that the magnitude of Shmin at ~0.93 km depth is 0.61 of the calculated vertical stress. Coulomb failure calculations using these stresses together with measurements of friction and permeability on core predict that dilatant shear failure should be induced on pre-existing conjugate normal faults once pore pressures are increased ~2.5 MPa or more above ambient values, generating a zone of enhanced permeability elongated in the direction toward active geothermal wells ~0.5 km to the SSW. Hydraulic stimulation of well 27-15 began in September 2010 by injecting water into the open-hole interval between the casing shoe at 0.9 km depth and a temporary cement plug at 1.1 km. Stimulation was monitored by combined surface and down-hole seismic monitoring, inter-well tracer testing and periodic pressure-temperature-flowmeter logging. An initial stage of low-pressure (shear) stimulation was conducted for ~100 days at a series of pressure steps Shmin and injection rates up to 2800 l/min, resulting in an additional 6-fold increase in injectivity. Numerous microearthquakes induced during this high-pressure stage along with tracer testing demonstrated growth of the stimulated volume and establishment of a strong hydrologic connection between well 27-15 and geothermal production wells to the SSW. After drilling out the cement plug and opening up the stimulation zone to the total depth of the well (1.8 km), additional stages of low- and high-pressure stimulation were carried out in early 2013. This full-hole stimulation was characterized by continued growth of the microseismic cloud in the NNE - SSW direction and strong tracer returns to the main geothermal field. A cumulative 175-fold injectivity gain was achieved in well 27-15 over the entire EGS project, which exceeded project goals. The Desert Peak geomechanical model predicted both the approximate initiation criteria and directional characteristics of the injection-induced shear and tensile failure and resulting permeability gains that led to success of this EGS project.

Hickman, S. H.; Davatzes, N. C.; Zemach, E.; Chabora, E.; Lutz, S.; Rose, P.; Majer, E. L.; Robertson-Tait, A.

2013-12-01

89

Variation in sericite composition from fracture zones within the Coso Hot Sprints geothermal system  

SciTech Connect

Two types of white micas are found in drill hole samples within the geothermal system at Coso Hot Springs. Low-permeability zones of the crystalline basement contain coarse-grained relict muscovite, whereas rock alteration near fracture zones at temperatures > 150/sup 0/C is characterized by abundant fine-grained sericite in association with secondary calcite and quartz and unaltered relict microcline. In this hydrothermal sericite there is an increase in interlayer K, octahedral Mg + Fe/sub total/ and tetrahedral Al with increasing temperature between approx. 215/sup 0/ to >250/sup 0/C. Thermodynamic activity of the Al/sub 2/Si/sub 4/O/sub 10/(OH)/sub 2/ component of sericites, calculated using site-mixing approximations of HELGESON and AAGAARD (1985), decreases with increasing temperature between approx. 215/sup 0/ and >250/sup 0/C. Although the compositions of hydrothermal sericites are a complex function of temperature, pressure and geothermal fluid composition, compositional relations observed at Coso together with published compositions of hydrothermal dioctahedral layer-silicates from the Salton Sea geothermal system demonstrates that elemental compositions of interlayer K and tetrahedral Al increase systematically with increasing temperature despite the dramatic differences in fluid compositions between these two geothermal systems. This suggests that the observed variations in interlayer and tetrahedral site occupancy is largely dependent on the enthalpy of hydrolysis reactions representing equilibrium between sericite solid solutions and the geothermal reservoir fluids.

Bishop, B.P.; Bird, D.K.

1987-05-01

90

Documentation of the status of international geothermal power plants and a list by country of selected geothermally active governmental and private sector entities  

SciTech Connect

This report includes the printouts from the International Geothermal Power Plant Data Base and the Geothermally Active Entity Data Base. Also included are the explanation of the abbreviations used in the power plant data base, maps of geothermal installations by country, and data base questionnaires and mailing lists.

Not Available

1992-10-01

91

A market survey of geothermal wellhead power generation systems  

NASA Technical Reports Server (NTRS)

The market potential for a portable geothermal wellhead power conversion device is assessed. Major study objectives included identifying the most promising applications for such a system, the potential impediments confronting their industrialization, and the various government actions needed to overcome these impediments. The heart of the study was a series of structured interviews with key decision-making individual in the various disciplines of the geothermal community. In addition, some technical and economic analyses of a candidate system were performed to support the feasibility of the basic concept.

Leeds, M. W.

1978-01-01

92

Variation in sericite compositions from fracture zones within the Coso Hot Springs geothermal system  

NASA Astrophysics Data System (ADS)

Two types of white micas are found in drillhole samples within the geothermal system at Coso Hot Springs. Low-permeability zones of the crystalline basement contain coarse-grained relict muscovite, whereas rock alteration near fracture zones at temperatures > 150°C is characterized by abundant finegrained sericite in association with secondary calcite and quartz and unaltered relict microcline. In this hydrothermal sericite there is an increase in interlayer K, octahedral Mg + Fetotal and tetrahedral Al with increasing temperature between ~215° to >250°C. Thermodynamic activity of the Al 2Si 4O 10(OH) 2 component of serielles, calculated using site-mixing approximations of HELGESON and AAGAARD (1985), decreases with increasing temperature between ~215° and >250°C. As a consequence of the observed variations in the interlayer, octahedral and tetrahedral site occupancies, the activity of KAl 2(AlSi 3O 10(OH) 2 is essentially constant in the Coso seriates over this temperature range. The calculated equilibrium distribution of aqueous species in the hydrothermal solutions produced from well 16-8, together with cation-activity phase diagrams that account for variations in sericite composition, requires a pH of ~6.7-6.8 at temperatures between 236° and 250°C. Comparison of predicted and observed phase relations with fluid compositions indicate that seriates are in local equilibrium with the geothermal reservoir fluid, whereas relict metamorphic muscovites are metastable. Although the compositions of hydrothermal sericites are a complex function of temperature, pressure and geothermal fluid composition, compositional relations observed at Coso together with published compositions of hydrothermal dioctahedral layer-silicates from the Salton Sea geothermal system demonstrates that elemental compositions of interlayer K and tetrahedral Al increase systematically with increasing temperature despite the dramatic differences in fluid compositions between these two geothermal systems. This suggests that the observed variations in interlayer and tetrahedral site occupancy is largely dependent on the enthalpy of hydrolysis reactions representing equilibrium between sericite solid solutions and the geothermal reservoir fluids.

Bishop, Barbara P.; Bird, Dennis K.

1987-05-01

93

Reno Industrial Park geothermal district heating system  

Microsoft Academic Search

Ten miles south of Reno, on U.S. 395 near the junction of the road to historic Virginia City, is Steamboat Hot Springs, a popular stop for travelers since the mid-1800s. Legend has it that Mark Twain named the geothermal area because it looked and sounded like a chugging Mississippi River paddle-wheeler. It is said when he first saw the steam

Paul J. Lienau

1997-01-01

94

Mathematical modeling of the behavior of geothermal systems under exploitation  

SciTech Connect

Analytical and numerical methods have been used in this investigation to model the behavior of geothermal systems under exploitation. The work is divided into three parts: (1) development of a numerical code, (2) theoretical studies of geothermal systems, and (3) field applications. A new single-phase three-dimensional simulator, capable of solving heat and mass flow problems in a saturated, heterogeneous porous or fractured medium has been developed. The simulator uses the integrated finite difference method for formulating the governing equations and an efficient sparse solver for the solution of the linearized equations. In the theoretical studies, various reservoir engineering problems have been examined. These include (a) well-test analysis, (b) exploitation strategies, (c) injection into fractured rocks, and (d) fault-charged geothermal reservoirs.

Bodvarsson, G.S.

1982-01-01

95

Recent Development of HFR Geothermal Reservoir System in Australia  

NASA Astrophysics Data System (ADS)

Since the 1970's, a number of research programmes have worked towards developing Hot Dry Rock technology (HDR) for geothermal energy which has been renamed as Hot Fractured Rock (HFR) in Australia. The HFR energy resource has the potential to supply base-load power with no greenhouse gas emissions. This paper will introduce the recent development of HFR geothermal reservoir system in Australia and focus on our related outcomes on numerical software development and field site operation as follows: (1). Geodynamics Limited is continuing to develop a world-class, high-grade geothermal energy resource contained in high temperature granites beneath the Cooper Basin in NE South Australia, which represents the largest known geothermal resource in the world and has the potential to supply 1000's MWe of low cost power to the national grid. The first deep well has reached a depth of over 4,400m, with temperatures exceeding 250ºC. Subsequent to drilling the well, a hydraulic stimulation programme resulted in the development of a large underground heat exchanger(reservoir). The encountered conditions of the hot granite are more favourable than expected. The economic feasibility of extracting heat from this reservoir will be established through a circulation test at 4,500m with the drilling of the production well. (2) Geothermal reservoir system as above involves the thermal, fluid and mechanical behaviour of geo-materials and natural seismic events, and potential geological perturbations to the geothermal reservoir. With the ARC Linkage grant, a 3D finite element based computational model and software for simulating a multi-scale highly coupled thermo-hydro-mechanical geo-mechanical system on the parallel supercomputer are being developed and preliminarily applied to analyze the Cooper Basin based on the available filed site data as above.

Xing, H.; Wyborn, D.; Xu, H.; Yin, C.; Mora, P.

2006-12-01

96

Prediction of Reinjection Effects on the Cerro Prieto Geothermal System.  

National Technical Information Service (NTIS)

The response of the Cerro Prieto geothermal field to different reinjection schemes is predicted using a two-dimensional vertical reservoir model with single- or two-phase flow. The advance of cold fronts and pressure changes in the system associated with ...

C. F. Tsang D. C. Mangold C. Doughty M. J. Lippmann

1982-01-01

97

Chemical and structural dynamics of a geothermal system  

Microsoft Academic Search

In an ongoing project to relate surface hydrothermal alteration to structurally controlled geothermal aquifers, we mapped a 16 km swath of the eastern front of the Stillwater Range using Hyperspectral fault and mineral mapping techniques. The Dixie Valley Fault system produces a large fractured aquifer heating Pleistocene aged groundwater to a temperature of 285° C at 5-6 km. Periodically over

T. Kennedy-Bowdoin; E. A. Silver; B. A. Martini; W. L. Pickles

2004-01-01

98

Tectonic and Structural Controls of Geothermal Activity in the Great Basin Region, Western USA  

NASA Astrophysics Data System (ADS)

We are conducting a thorough inventory of structural settings of geothermal systems (>400 total) in the extensional to transtensional Great Basin region of the western USA. Most of the geothermal systems in this region are not related to upper crustal magmatism and thus regional tectonic and local structural controls are the most critical factors controlling the locations of the geothermal activity. A system of NW-striking dextral faults known as the Walker Lane accommodates ~20% of the North American-Pacific plate motion in the western Great Basin and is intimately linked to N- to NNE-striking normal fault systems throughout the region. Overall, geothermal systems are concentrated in areas with the highest strain rates within or proximal to the eastern and western margins of the Great Basin, with the high temperature systems clustering in transtensional areas of highest strain rate in the northwestern Great Basin. Enhanced extension in the northwestern Great Basin probably results from the northwestward termination of the Walker Lane and the concomitant transfer of dextral shear into west-northwest directed extension, thus producing a broad transtensional region. The capacity of geothermal power plants also correlates with strain rates, with the largest (hundreds of megawatts) along the Walker Lane or San Andreas fault system, where strain rates range from 10-100 nanostrain/yr to 1,000 nanostrain/yr, respectively. Lesser systems (tens of megawatts) reside in the Basin and Range (outside the Walker Lane), where local strain rates are typically < 10 nanostrain/yr. Of the 250+ geothermal fields catalogued, step-overs or relay ramps in normal fault zones serve as the most favorable setting, hosting ~32% of the systems. Such areas have multiple, overlapping fault strands, increased fracture density, and thus enhanced permeability. Other common settings include a) intersections between normal faults and strike-slip or oblique-slip faults (27%), where multiple minor faults connect major structures and fluids can flow readily through highly fractured, dilational quadrants, and b) normal fault terminations or tip-lines (22%), where horse-tailing generates closely-spaced faults and increased permeability. Other settings include accommodation zones (i.e., belts of intermeshing, oppositely dipping normal faults; 8%), major range-front faults (5-6%), and pull-aparts in strike-slip faults (4%). In addition, Quaternary faults lie within or near most systems. The relative scarcity of geothermal systems along displacement-maxima of major normal faults may be due to reduced permeability in thick zones of clay gouge and periodic release of stress in major earthquakes. Step-overs, terminations, intersections, and accommodation zones correspond to long-term, critically stressed areas, where fluid pathways are more likely to remain open in networks of closely-spaced, breccia-dominated fractures. These findings may help guide future exploration efforts, especially for blind geothermal systems, which probably comprise the bulk of the geothermal resources in the Great Basin.

Faulds, J. E.; Hinz, N.; Kreemer, C. W.

2012-12-01

99

The importance of COâ on freezing point measurements of fluid inclusions: evidence from active geothermal systems and implications for epithermal ore deposition  

Microsoft Academic Search

The authors show how the melting point of ice may be calculated for a fluid of known composites. Fluid inclusion ice-melting data from New Zealand geothermal fields correlate well with values calculated using the equation presented and the measured compositions of discharges from wells from which the inclusion samples were obtained. Loss of the dominant dissolved gas, COâ during boiling

J. W. Hedenquist; R. W. Henley

1985-01-01

100

COTHERM: Geophysical Modeling of High Enthalpy Geothermal Systems  

NASA Astrophysics Data System (ADS)

In recent years geothermal heating and electricity generation have become an attractive alternative energy resource, especially natural high enthalpy geothermal systems such as in Iceland. However, the financial risk of installing and operating geothermal power plants is still high and more needs to be known about the geothermal processes and state of the reservoir in the subsurface. A powerful tool for probing the underground system structure is provided by geophysical techniques, which are able to detect flow paths and fracture systems without drilling. It has been amply demonstrated that small-scale features can be well imaged at shallow depths, but only gross structures can be delineated for depths of several kilometers, where most high enthalpy systems are located. Therefore a major goal of our study is to improve geophysical mapping strategies by multi-method geophysical simulations and synthetic data inversions, to better resolve structures at greater depth, characterize the reservoir and monitor any changes within it. The investigation forms part of project COTHERM - COmbined hydrological, geochemical and geophysical modeling of geoTHERMal systems - in which a holistic and synergistic approach is being adopted to achieve multidisciplinary cooperation and mutual benefit. The geophysical simulations are being performed in combination with hydrothermal fluid flow modeling and chemical fluid rock interaction modeling, to provide realistic constraints on lithology, pressure, temperature and fluid conditions of the subsurface. Two sites in Iceland have been selected for the study, Krafla and Reykjanes. As a starting point for the geophysical modeling, we seek to establish petrophysical relations, connecting rock properties and reservoir conditions with geophysical parameters such as seismic wave speed, attenuation, electrical conductivity and magnetic susceptibility with a main focus on seismic properties. Therefore, we follow a comprehensive approach involving three components: (1) A literature study to find relevant, existing theoretical models, (2) laboratory determinations to confirm their validity for Icelandic rocks of interest and (3) a field campaign to obtain in-situ, shallow rock properties from seismic and resistivity tomography surveys over a fossilized and exhumed geothermal system. Theoretical models describing physical behavior for rocks with strong inhomogeneities, complex pore structure and complicated fluid-rock interaction mechanisms are often poorly constrained and require the knowledge about a wide range of parameters that are difficult to quantify. Therefore we calibrate the theoretical models by laboratory measurements on samples of rocks, forming magmatic geothermal reservoirs. Since the samples used in the laboratory are limited in size, and laboratory equipment operates at much higher frequency than the instruments used in the field, the results need to be up-scaled from the laboratory scale to field scale. This is not a simple process and entails many uncertainties.

Grab, Melchior; Maurer, Hansruedi; Greenhalgh, Stewart

2014-05-01

101

Numerical modeling of geothermal systems with applications to Krafla, Iceland and Olkaria, Kenya  

SciTech Connect

The use of numerical models for the evaluation of the generating potential of high temperature geothermal fields has increased rapidly in recent years. In the present paper a unified numerical approach to the modeling of geothermal systems is discussed and the results of recent modeling of the Krafla geothermal field in Iceland and the Olkaria, Kenya, are described. Emphasis is placed on describing the methodology using examples from the two geothermal fields.

Bodvarsson, G.S.

1987-08-01

102

Life-cycle analysis results for geothermal systems in comparison to other power systems: Part II.  

SciTech Connect

A study has been conducted on the material demand and life-cycle energy and emissions performance of power-generating technologies in addition to those reported in Part I of this series. The additional technologies included concentrated solar power, integrated gasification combined cycle, and a fossil/renewable (termed hybrid) geothermal technology, more specifically, co-produced gas and electric power plants from geo-pressured gas and electric (GPGE) sites. For the latter, two cases were considered: gas and electricity export and electricity-only export. Also modeled were cement, steel and diesel fuel requirements for drilling geothermal wells as a function of well depth. The impact of the construction activities in the building of plants was also estimated. The results of this study are consistent with previously reported trends found in Part I of this series. Among all the technologies considered, fossil combustion-based power plants have the lowest material demand for their construction and composition. On the other hand, conventional fossil-based power technologies have the highest greenhouse gas (GHG) emissions, followed by the hybrid and then two of the renewable power systems, namely hydrothermal flash power and biomass-based combustion power. GHG emissions from U.S. geothermal flash plants were also discussed, estimates provided, and data needs identified. Of the GPGE scenarios modeled, the all-electric scenario had the highest GHG emissions. Similar trends were found for other combustion emissions.

Sullivan, J.L.; Clark, C.E.; Yuan, L.; Han, J.; Wang, M. (Energy Systems)

2012-02-08

103

COTHERM: Modelling fluid-rock interactions in Icelandic geothermal systems  

NASA Astrophysics Data System (ADS)

Mineralogical alteration of reservoir rocks, driven by fluid circulation in natural or enhanced geothermal systems, is likely to influence the long-term performance of geothermal power generation. A key factor is the change of porosity due to dissolution of primary minerals and precipitation of secondary phases. Porosity changes will affect fluid circulation and solute transport, which, in turn, influence mineralogical alteration. This study is part of the Sinergia COTHERM project (COmbined hydrological, geochemical and geophysical modeling of geotTHERMal systems) that is an integrative research project aimed at improving our understanding of the sub-surface processes in magmatically-driven natural geothermal systems. We model the mineralogical and porosity evolution of Icelandic geothermal systems with 1D and 2D reactive transport models. These geothermal systems are typically high enthalphy systems where a magmatic pluton is located at a few kilometers depth. The shallow plutons increase the geothermal gradient and trigger the circulation of hydrothermal waters with a steam cap forming at shallow depth. We investigate two contrasting geothermal systems: Krafla, for which the water recharge consists of meteoritic water; and Reykjanes, for which the water recharge mainly consists of seawater. The initial rock composition is a fresh basalt. We use the GEM-Selektor geochemical modeling package [1] for calculation of kinetically controlled mineral equilibria between the rock and the ingression water. We consider basalt minerals dissolution kinetics according to Palandri & Kharaka [2]. Reactive surface areas are assumed to be geometric surface areas, and are corrected using a spherical-particle surface/mass relationship. For secondary minerals, we consider the partial equilibrium assuming that the primary mineral dissolution is slow, and the secondary mineral precipitation is fast. Comparison of our modeling results with the mineralogical assemblages observed in the field by Gudmundsson & Arnorsson [3] and by Icelandic partners of the COTHERM project suggests that the concept of partial equilibrium with instantaneous precipitation of secondary minerals is not sufficient to satisfactorily describe the experimental data. Considering kinetic controls also for secondary minerals appears as indispensable to properly describe the geothermal system evolution using a reactive transport modelling approach [4]. [1] Kulik D.A., Wagner T., Dmytrieva S.V., Kosakowski G., Hingerl F.F., Chudnenko K.V., Berner U., 2013. GEM-Selektor geochemical modeling package: revised algorithm and GEMS3K numerical kernel for coupled simulation codes. Computational Geosciences 17, 1-24. http://gems.web.psi.ch. [2] Palandri, J.L., Kharaka, Y.K., 2004. A compilation of rate parameters of water-mineral interaction kinetics for application to geochemical modelling. U.S.Geological Survey, Menlo Park, CA, pp. 1-64. [3] Gudmundsson B.T., Arnorsson S., 2005. Secondary mineral-fluid equilibria in the Krafla and Namafjall geothermal systems, Iceland. Applied Geochememistry 20, 1607-1625. [4] Kosakowski, G., & Watanabe, N., 2013. OpenGeoSys-Gem: A numerical tool for calculating geochemical and porosity changes in saturated and partially saturated media. Physics and Chemistry of the Earth, Parts A/B/C. doi:10.1016/j.pce.2013.11.008

Thien, Bruno; Kosakowski, Georg; Kulik, Dmitrii

2014-05-01

104

Direct utilization of geothermal heat in cascade application to aquaculture and greenhouse systems at Navarro College. Final report, March 1, 1979September 30, 1984  

Microsoft Academic Search

This final report documents the Navarro College geothermal use project, which is one of nineteen direct-use geothermal projects funded principally by DOE. The six-year project encompassed a broad range of technical, institutional, and economic activities including: resource and environmental assessment; well drilling and completion; system design, construction, and monitoring; economic analysis; and public awareness programs. Some of the project conclusions

1984-01-01

105

Evaluating Geothermal Potential in Germany by Numerical Reservoir Modeling of Engineered Geothermal Systems  

NASA Astrophysics Data System (ADS)

We model hypothetical Engineered Geothermal System (EGS) reservoirs by solving coupled partial differential equations governing fluid flow and heat transport. Building on EGS's strengths of inherent modularity and storage capability, it is possible to implement multiple wells in the reservoir to extend the rock volume accessible for circulating water in order to increase the heat yield. By varying parameters like flow rates and well-separations in the subsurface, this study looks at their long-term impacts on the reservoir development. This approach allows us to experiment with different placements of the engineered fractures and propose several EGS layouts for achieving optimized heat extraction. Considering the available crystalline area and accounting for the competing land uses, this study evaluates the overall EGS potential and compares it with those of other used renewables in Germany. There is enough area to support 13450 EGS plants, each with six reversed-triplets (18 wells) and an average electric power of 35.3MWe. When operated at full capacity, these systems can collectively supply 4155TWh of electric energy in one year which would be roughly six times the electric energy produced in Germany in the year 2011. Engineered Geothermal Systems make a compelling case for contributing towards national power production in a future powered by a sustainable, decentralized energy system.

Jain, Charitra; Vogt, Christian; Clauser, Christoph

2014-05-01

106

Engineered Geothermal Systems Energy Return On Energy Investment  

SciTech Connect

Energy Return On Investment (EROI) is an important figure of merit for assessing the viability of energy alternatives. Too often comparisons of energy systems use â??efficiencyâ? when EROI would be more appropriate. For geothermal electric power generation, EROI is determined by the electricity delivered to the consumer compared to the energy consumed to construct, operate, and decommission the facility. Critical factors in determining the EROI of Engineered Geothermal Systems (EGS) are examined in this work. These include the input energy embodied into the system. Embodied energy includes the energy contained in the materials, as well as, that consumed in each stage of manufacturing from mining the raw materials to assembling the finished system. Also critical are the system boundaries and value of the energy â?? heat is not as valuable as electrical energy. The EROI of an EGS depends upon a number of factors that are currently unknown, for example what will be typical EGS well productivity, as well as, reservoir depth, temperature, and temperature decline rate. Thus the approach developed is to consider these factors as parameters determining EROI as a function of number of wells needed. Since the energy needed to construct a geothermal well is a function of depth, results are provided as a function of well depth. Parametric determination of EGS EROI is calculated using existing information on EGS and US Department of Energy (DOE) targets and is compared to the â??minimumâ? EROI an energy production system should have to be an asset rather than a liability.

Mansure, A J

2012-12-10

107

Community Geothermal Technology Program: Bottom heating system using geothermal power for propagation. Final report, Phases 1 and 2  

SciTech Connect

The objective is to develop and study a bottom-heating system in a greenhouse utilizing geothermal energy to aid germination and speed growth of palms. Source of heat was geothermal brine from HGP-A well. The project was successful; the heat made a dramatic difference with certain varieties, such as Areca catechu (betelnut) with 82% germination with heat, zero without. For other varieties, germination rates were much closer. Quality of seed is important. Tabs, figs.

Downing, J.C.

1990-01-01

108

GEOLOGIC SETTING OF THE CHENA HOT SPRINGS GEOTHERMAL SYSTEM, ALASKA  

Microsoft Academic Search

A belt of moderate-temperature geothermal activity runs east-west across central Alaska. Chena Hot Springs (CHS) is one of several Interior Alaskan hot springs in or near 55 Ma granites within Paleozoic metamorphic rocks. CHS is located within the CHS pluton, a composite body of quartz diorite, tonalite, granodiorite, and granite of both mid-Cretaceous and Early Tertiary ages. 40Ar\\/39Ar step heat

Amanda Kolker; Rainer Newberry; Jessica Larsen; Paul Layer; Patrick Stepp

2007-01-01

109

Direct utilization of geothermal heat in cascade application to aquaculture and greenhouse systems at Navarro College. Final report, March 1, 1979-September 30, 1984  

SciTech Connect

This final report documents the Navarro College geothermal use project, which is one of nineteen direct-use geothermal projects funded principally by DOE. The six-year project encompassed a broad range of technical, institutional, and economic activities including: resource and environmental assessment; well drilling and completion; system design, construction, and monitoring; economic analysis; and public awareness programs. Some of the project conclusions are that: (1) the 130/sup 0/F Central Texas geothermal resource can support additional geothermal development; (2) private sector economic incentives currently exist which encourage commercial development of this geothermal resource; (3) potential uses for this geothermal resource include water and space heating, aquacultural and agricultural heating uses, and fruit and vegetable dehydration; (4) high maintenance costs arising from the geofluids' scaling and corrosion characteristics can be avoided through proper analysis and design.

Smith, K.

1984-09-01

110

Thermally conductive cementitious grout for geothermal heat pump systems  

DOEpatents

A thermally conductive cement-sand grout for use with a geothermal heat pump system. The cement sand grout contains cement, silica sand, a superplasticizer, water and optionally bentonite. The present invention also includes a method of filling boreholes used for geothermal heat pump systems with the thermally conductive cement-sand grout. The cement-sand grout has improved thermal conductivity over neat cement and bentonite grouts, which allows shallower bore holes to be used to provide an equivalent heat transfer capacity. In addition, the cement-sand grouts of the present invention also provide improved bond strengths and decreased permeabilities. The cement-sand grouts can also contain blast furnace slag, fly ash, a thermoplastic air entraining agent, latex, a shrinkage reducing admixture, calcium oxide and combinations thereof.

Allan, Marita (Old Field, NY)

2001-01-01

111

High Temperature Components of Magma-Related Geothermal Systems: An Experimental and Theoretical Approach  

SciTech Connect

This summarizes select components of a multi-faceted study of high temperature magmatic fluid behavior in shallow, silicic, volcano-plutonic geothermal systems. This work built on a foundation provided by DOE-supported advances made in our lab in understanding the physics and chemistry of the addition of HCI and other chlorides into the high temperature regions of geothermal systems. The emphasis of this project was to produce a model of the bolatile contributions from felsic magmatic systems to geothermal systems

Philip A. Candela; Philip M. Piccoli

2004-03-15

112

Geothermal district heating system feasibility analysis, Thermopolis, Wyoming  

SciTech Connect

The purpose of this study is to determine the technical and economic feasibility of constructing and operating a district heating system to serve the residential, commercial, and public sectors in Thermopolis. The project geothermal resource assessment, based on reviews of existing information and data, indicated that substantial hot water resources likely exist in the Rose Dome region 10 miles northeast of Thermopolis, and with quantities capable of supporting the proposed geothermal uses. Preliminary engineering designs were developed to serve the space heating and hot water heating demands for buildings in the Thermopolis-East Thermopolis town service area. The heating district design is based on indirect geothermal heat supply and includes production wells, transmission lines, heat exchanger units, and the closed loop distribution and collection system necessary to serve the individual customers. Three options are presented for disposal of the cooled waters-reinjection, river disposal, and agricultural reuse. The preliminary engineering effort indicates the proposed system is technically feasible. The design is sized to serve 1545 residences, 190 businesses, and 24 public buildings. The peak design meets a demand of 128.2 million Btu at production rates of 6400 gpm.

Goering, S.W.; Garing, K.L.; Coury, G.; Mickley, M.C.

1982-04-26

113

Geothermal Energy.  

ERIC Educational Resources Information Center

Major activities, programs, and conferences in geothermal energy during 1982 are highlighted. These include first comprehensive national assessment of U.S. low-temperature geothermal resources (conducted by U.S. Geological Survey and Department of Energy), map production by U.S. Geological Survey, geothermal plant production, and others. (JN)

Bufe, Charles Glenn

1983-01-01

114

Geothermal Energy Program overview  

SciTech Connect

The mission of the Geothermal Energy Program is to develop the science and technology necessary for tapping our nation's tremendous heat energy sources contained with the Earth. Geothermal energy is a domestic energy source that can produce clean, reliable, cost- effective heat and electricity for our nation's energy needs. Geothermal energy -- the heat of the Earth -- is one of our nation's most abundant energy resources. In fact, geothermal energy represents nearly 40% of the total US energy resource base and already provides an important contribution to our nation's energy needs. Geothermal energy systems can provide clean, reliable, cost-effective energy for our nation's industries, businesses, and homes in the form of heat and electricity. The US Department of Energy's (DOE) Geothermal Energy Program sponsors research aimed at developing the science and technology necessary for utilizing this resource more fully. Geothermal energy originates from the Earth's interior. The hottest fluids and rocks at accessible depths are associated with recent volcanic activity in the western states. In some places, heat comes to the surface as natural hot water or steam, which have been used since prehistoric times for cooking and bathing. Today, wells convey the heat from deep in the Earth to electric generators, factories, farms, and homes. The competitiveness of power generation with lower quality hydrothermal fluids, geopressured brines, hot dry rock, and magma ( the four types of geothermal energy) still depends on the technical advancements sought by DOE's Geothermal Energy Program.

Not Available

1991-12-01

115

Development of Exploration Methods for Engineered Geothermal Systems  

NASA Astrophysics Data System (ADS)

The principle objective of an exploration program is to identify exploration drilling targets that will advance a prospect towards development and full-scale production or relinquish interest in the prospect. Engineered Geothermal Systems (EGS) exploration key geoscience parameters are temperature, lithology, and stress state at an economically feasible target depth. Our project tests the hypothesis that our proposed exploration methodology will identify potential EGS drilling targets at Dixie Valley. Dixie Valley was chosen as the test calibration site because it is a highly characterized geothermal resource was a sufficiently large database in the public domain. U.S. Department of Energy Geothermal Technologies Program under the American Recovery and Reinvestment Act has awarded funding to AltaRock to develop exploration methods for EGS by integrating geophysical, geological, and geochemical data sets. New seismic, gravity, magnetotellurics (MT), and geochemical data will be collected and integrated into the model to improve model coverage and resolution. Other model inputs will include geology, fault-kinematics, fracture-characterization, and earthquake fault-plane solutions to provide information on stress state. Where appropriate, additional geochemical measurements will be made to model geo-thermal temperatures at depth. The resulting integrated data model will be used to predict the EGS parameters of interest (temperature, lithology and stress state) with greater certainty and a "higher degree of non-uniqueness” across the test area. We hypothesize that successful EGS drilling targets will be identifiable through integration of existing and new geoscience data coupled with geostatictical and Subject Matter Expertise. Both the existing and the existing plus new data will be integrated into separate data models on a 5x5km grid with 1 km depth slices. The results of each data model will be evaluated for the degree of improvement relative to the parameters of interest.

Iovenitti, J. L.; Tibuleac, I. M.; Hopkins, D.; Cladouhos, T.; Karlin, R. E.; Wannamaker, P. E.; Kennedy, B. M.; Blackwell, D. D.; Clyne, M.

2010-12-01

116

Hydrocarbon anomaly in soil gas as near-surface expressions of upflows and outflows in geothermal systems  

SciTech Connect

A variety of hydrocarbons, C1 - C12, have been found in volcanic gases (fumarolic) and in geothermal waters and gases. The hydrocarbons are thought to have come from products of pyrolysis of kerogen in sedimentary rocks or they could be fed into the geothermal system by the recharging waters which may contain dissolved hydrocarbons or hydrocarbons extracted by the waters from the rocks. In the hot geothermal zone, 300°+ C, many of these hydrocarbons are in their critical state. It is thought that they move upwards due to buoyancy and flux up with the upflowing geothermal fluids in the upflow zones together with the magmatic gases. Permeability which could be provided by faults, fissures, mini and micro fractures are thought to provide pathways for the upward flux. A sensitive technique (Petrex) utilizing passive integrative adsorption of the hydrocarbons in soil gas on activated charcoal followed by desorption and analysis of the hydrocarbons by direct introduction mass spectrometry allows mapping of the anomalous areas. Surveys for geothermal resources conducted in Japan and in Indonesia show that the hydrocarbon anomaly occur over known fields and over areas strongly suspected of geothermal potential. The hydrocarbons found and identified were n-paraffins (C7-C9) and aromatics (C7-C8). Detection of permeable, i.e. active or open faults, parts of older faults which have been reactivated, e.g. by younger intersecting faults, and the area surrounding these faulted and permeable region is possible. The mechanism leading to the appearance of the hydrocarbon in the soil gas over upflow zones of the geothermal reservoir is proposed. The paraffins seems to be better pathfinders for the location of upflows than the aromatics. However the aromatics may, under certain circumstances, give better indications of the direction of the outflow of the geothermal system. It is thought that an upflow zone can be defined when conditions exist where the recharging waters containing the hydrocarbons feed into the geothermal kitchen. The existence of open and active faults, fissures, mini and micro fractures allow sufficient permeability for the gases to flux up and express themselves at the surface as hydrocarbon anomaly in the soil gas. When any of the requirements is absent, i.e. in the absence of the recharging waters, hydrocarbons, temperature, or permeability, no anomaly can be expected. It assumes a dynamic convective system, i.e. recharging waters, upflow and outflow. The anomalies however can define to a certain extent, regions of geothermal upflow, buoyant transport of gases, and frequently down-gradient of cooling waters.

Ong, H.L.; Higashihara, M.; Klusman, R.W.; Voorhees, K.J.; Pudjianto, R.; Ong, J

1996-01-24

117

Seismic ambient noise study at Bouillante geothermal system, French Antilles  

NASA Astrophysics Data System (ADS)

Seismic ambient noise analyses have been shown to be able to image structural features of the crust and to monitor underground changes of seismic wave ground velocity. We present results of cross-correlation techniques at Bouillante geothermal field, French Antilles, the largest French high-enthalpy geothermal system exploited for electrical power from 3 collocated productive wells. Two power plants generate electricity and fluid extraction rate varies with time and wells are sometimes closed for equipment maintenance. Under the support of the French Environment and Energy Management Agency (ADEME) and the French Research Agency (ANR), BRGM has been analyzing seismic data from a network comprising 5 broadband seismological stations set-up at Bouillante area since 2004. Amongst the large number of earthquakes recorded, we show that no single earthquake could be related to the fluid exploitation. Instead, they are due to the intense regional seismicity. Despite the small number of stations, surface wave travel times computed from ambient noise cross-correlation for about a year suggest that the velocity structure is consistent with the conceptual model of hot (250°C) and permeable (fractured) geothermal reservoir of Bouillante. We show at several instances that changes of the fluid extraction rate have spatial and temporal slight perturbations on medium wave velocity. For example, when the production stops for maintenance, velocity increases by several percent and with larger amplitude at stations within 1 km distance from the production wells and lower amplitudes (by more than 50 %) at stations further than 2 km from the production wells. In addition, we note that velocity perturbations have a delay of at most 1 day at further stations. We discuss several mechanisms to explain those observations like pressure and stress variations in the geothermal system. The results suggest that the inferred velocity changes, owing the fine sensibility of the inter-correlation method, do not produce stress changes strong enough to trigger micro-seismicity in the Bouillante area. The perturbation (e.g., due to phase change in the hot fluid, change in porosity and fracture closure) would propagate through the fracture system with a speed depending on its structural features. More observations using additional stations would allow us to increase our knowledge of the velocity structure around the geothermal field and understand physical mechanisms behind those controlled perturbations.

Jousset, Philippe; Bitri, Adnan; Loiseau, Justine; Bouchot, Vincent

2010-05-01

118

Thermal Infrared Remote Sensing of the Yellowstone Geothermal System  

NASA Astrophysics Data System (ADS)

The Yellowstone National Park (YNP) geothermal system is one of the largest in the world, with thousands of individual thermal features ranging in size from a few centimeters to tens of meters across, (e.g., fumaroles, geysers, mud pots and hot spring pools). Together, large concentrations of these thermal features make up dozens of distinct thermal areas, characterized by sparse vegetation, hydrothermally altered rocks, and usually either sinter, travertine, or acid sulfate alteration. The temperature of these thermal features generally ranges from ~30 to ~93 oC, which is the boiling temperature of water at the elevation of Yellowstone. In-situ temperature measurements of various thermal features are sparse in both space and time, but they show a dynamic time-temperature relationship. For example, as geysers erupt and send pulses of warm water down slope, the warm water cools rapidly and is then followed by another pulse of warm water, on time scales of minutes. The total heat flux from the Park’s thermal features has been indirectly estimated from chemical analysis of Cl- flux in water flowing from Yellowstone’s rivers. We are working to provide a more direct measurement, as well as estimates of time variability, of the total heat flux using satellite multispectral thermal infrared (TIR) remote sensing data. Over the last 10 years, NASA’s orbiting ASTER and MODIS instruments have acquired hundreds and thousands of multispectral TIR images, respectively, over the YNP area. Compared with some volcanoes, Yellowstone is a relatively low-temperature geothermal system, with low thermal contrast to the non-geothermal surrounding areas; therefore we are refining existing techniques to extract surface temperature and thermal flux information. This task is complicated by issues such as, during the day, solar heated surfaces may be warmer than nearby geothermal features; and there is some topographic (elevation) influence on surface temperatures, even at night. Still we have been able to obtain temperature and heat flux values from small scale geothermal features with ASTER and some larger scale thermal areas with MODIS. The latest results of this study will be presented; including MODIS time-series data and examples of using higher spatial resolution ASTER data for identifying hot spots.

Vaughan, R. G.; Keszthelyi, L. P.; Heasler, H.; Jaworowski, C.; Lowenstern, J. B.; Schneider, D. J.

2009-12-01

119

I/S and C/S mixed layers, some indicators of recent physical-chemical changes in active geothermal systems: The case study of Chipilapa (El Salvador)  

SciTech Connect

I/S and C/S mixed layers from the geothermal field of Chipilapa (El Salvador) have been studied in details in order to reevaluate their potential use as indicator of the thermodynamic conditions in which they were formed. It is funded that overprinting of clay bearing alteration stages is common. For a given alteration stage, the spatial variation of I/S and C/S mixed layer ininerals is controlled by kinetics of mixed layer transformation and not only by temperature. Clay geo-thermometers cannot give reliable results because the present crystal-chemical states of the I/S and C/S mixed layers is not their initial state, it was aquired during the overall hydrothermal history which post dated the nucleation of smectitic clay material at high temperature. Occurrences of smectites or smectite-rich mixed layers at high temperature in reservoirs is a promising guide for reconstruct the zones in which boiling or mixing of non isotherinal fluids occurred very recently or still presently.

Beaufort, D.; Papapanagiotou, P.; patrier, P.; Fouillac, A.M.; Traineau, H.

1996-01-24

120

Is it only CO 2 that matters? A life cycle perspective on shallow geothermal systems  

Microsoft Academic Search

Shallow geothermal systems such as open and closed geothermal heat pump (GHP) systems are considered to be an efficient and renewable energy technology for cooling and heating of buildings and other facilities. The numbers of installed ground source heat pump (GSHP) systems, for example, is continuously increasing worldwide. The objective of the current study is not only to discuss the

Dominik Saner; Ronnie Juraske; Markus Kübert; Philipp Blum; Stefanie Hellweg; Peter Bayer

2010-01-01

121

National Geothermal Data System: State Geological Survey Contributions to Date  

NASA Astrophysics Data System (ADS)

In collaboration with the Association of American State Geologists the Arizona Geological Survey is leading the effort to bring legacy geothermal data to the U.S. Department of Energy's National Geothermal Data System (NGDS). NGDS is a national, sustainable, distributed, interoperable network of data and service (application) providers entering its final stages of development. Once completed the geothermal industry, the public, and policy makers will have access to consistent and reliable data, which in turn, reduces the amount of staff time devoted to finding, retrieving, integrating, and verifying information. With easier access to information, the high cost and risk of geothermal power projects (especially exploration drilling) is reduced. This presentation focuses on the scientific and data integration methodology as well as State Geological Survey contributions to date. The NGDS is built using the U.S. Geoscience Information Network (USGIN) data integration framework to promote interoperability across the Earth sciences community and with other emerging data integration and networking efforts. Core to the USGIN concept is that of data provenance; by allowing data providers to maintain and house their data. After concluding the second year of the project, we have nearly 800 datasets representing over 2 million data points from the state geological surveys. A new AASG specific search catalog based on popular internet search formats enables end users to more easily find and identify geothermal resources in a specific region. Sixteen states, including a consortium of Great Basin states, have initiated new field data collection for submission to the NGDS. The new field data includes data from at least 21 newly drilled thermal gradient holes in previously unexplored areas. Most of the datasets provided to the NGDS are being portrayed as Open Geospatial Consortium (OGC) Web Map Services (WMS) and Web Feature Services (WFS), meaning that the data is compatible with a variety of visualization software. Web services are ideal for the NGDS data for a number of reasons including that they preserve data ownership in that they are read only and new services can be deployed to meet new requirements without modifying existing applications.

Patten, K.; Allison, M. L.; Richard, S. M.; Clark, R.; Love, D.; Coleman, C.; Caudill, C.; Matti, J.; Musil, L.; Day, J.; Chen, G.

2012-12-01

122

Development of Geothermal-Well-Completion Systems. Final Report.  

National Technical Information Service (NTIS)

Results of a three year study concerning the completion of geothermal wells, specifically cementing, are reported. The research involved some specific tasks: (1) determination of properties an adequate geothermal well cement must possess; (2) thorough eva...

E. B. Nelson

1979-01-01

123

Prediction of reinjection effects on the Cerro Prieto geothermal system  

SciTech Connect

The response of the Cerro Prieto geothermal field to different reinjection schemes is predicted using a two-dimensional vertical reservoir model with single- or two-phase flow. The advance of cold fronts and pressure changes in the system associated with the inection operations are computed, taking into consideration the geologic characteristics of the field. The effects of well location, depth, and rates of injection are analyzed. Results indicate that significant pressure maintenance effects may be realized in a carefully designed reinjection operation.

Tsang, C.F.; Mangold, D.C.; Doughty, C.; Lippmann, M.J.

1982-08-10

124

Geothermal pump down-hole energy regeneration system  

DOEpatents

Geothermal deep well energy extraction apparatus is provided of the general kind in which solute-bearing hot water is pumped to the earth's surface from a subterranean location by utilizing thermal energy extracted from the hot water for operating a turbine motor for driving an electrical power generator at the earth 3 s surface, the solute bearing water being returned into the earth by a reinjection well. Efficiency of operation of the total system is increased by an arrangement of coaxial conduits for greatly reducing the flow of heat from the rising brine into the rising exhaust of the down-well turbine motor.

Matthews, Hugh B. (Boylston, MA)

1982-01-01

125

Long-term predictions of minewater geothermal systems heat resources  

NASA Astrophysics Data System (ADS)

Abandoned underground mines usually flood due to the natural rise of the water table. In most cases the process is relatively slow giving the mine water time to equilibrate thermally with the the surrounding rock massif. Typical mine water temperature is too low to be used for direct heating, but is well suited to be combined with heat pumps. For example, heat extracted from the mine can be used during winter for space heating, while the process could be reversed during summer to provide space cooling. Altough not yet widely spread, the use of low temperature geothermal energy from abandoned mines has already been implemented in the Netherlands, Spain, USA, Germany and the UK. Reliable reservoir modelling is crucial to predict how geothermal minewater systems will react to predefined exploitation schemes and to define the energy potential and development strategy of a large-scale geothermal - cold/heat storage mine water systems. However, most numerical reservoir modelling software are developed for typical environments, such as porous media (a.o. many codes developed for petroleum reservoirs or groundwater formations) and cannot be applied to mine systems. Indeed, mines are atypical environments that encompass different types of flow, namely porous media flow, fracture flow and open pipe flow usually described with different modelling codes. Ideally, 3D models accounting for the subsurface geometry, geology, hydrogeology, thermal aspects and flooding history of the mine as well as long-term effects of heat extraction should be used. A new modelling approach is proposed here to predict the long-term behaviour of Minewater geothermal systems in a reactive and reliable manner. The simulation method integrates concepts for heat and mass transport through various media (e.g., back-filled areas, fractured rock, fault zones). As a base, the standard software EPANET2 (Rossman 1999; 2000) was used. Additional equations for describing heat flow through the mine (both through open pipes and from the rock massif) have been implemented. Among others, parametric methods are used to bypass some shortcomings in the physical models used for the subsurface. The advantage is that the complete geometry of the mine workings can be integrated and that computing is fast enough to allow implementing and testing several scenarios (e.g. contributions from fault zones, different assumptions about the actual status of shafts, drifts and mined out areas) in an efficient way (Ferket et al., 2011). EPANET allows to incorporate the full complexity of the subsurface mine structure. As a result, the flooded mine is considered as a network of pipes, each with a custom-defined diameter, length and roughness.

Harcout-Menou, Virginie; de ridder, fjo; laenen, ben; ferket, helga

2014-05-01

126

One-dimensional model of vapor-dominated geothermal systems  

NASA Astrophysics Data System (ADS)

A one-dimensional model of vapor-dominated geothermal systems in the natural state is developed in order to study the ranges of the heat and mass transport and flow resistance at which a system is capable of existing in the vapor-dominated state. The model consists of a near-surface condensate layer lying above a two-phase counterflow region with rising steam and descending water in a porous saturated medium. Examination of models with condensate layers several hundred meters thick and reservoir temperatures near 513 K, characteristic of real systems, reveals them to have net mass flow rate/thermal conductivity ratios less than about 2.5 x 10 to the -7th K sec-squared/cu m and permeability/thermal conductivity ratios greater than 4.5 x 10 to the -17th m sec-cubed K/kg. Application of the model to the temperature and pressure data for the main reservoir of the Kawah Kamojang geothermal system in West Java indicates a permeability/thermal conductivity ratio between 10 to the -15th and 10 to the -14th m sec-cubed K/kg, or a permeability between 4 and 40 mdarcy for a thermal conductivity of 4 J/m per sec per K. Results also require the existence of a lower permeability cap overlying the higher permeability main reservoir in order to stabilize the water layer above the steam region.

Straus, J. M.; Schubert, G.

1981-10-01

127

Geothermal progress monitor report No. 6  

SciTech Connect

Geothermal Progress Monitor Report No. 6 presents a state-by-state summary of the status of geothermal leasing, exploration, and development in major physiographic regions where geothermal resource potential has been identified. Recent state-specific activities are reported at the end of each state status report, while recent activities of a more general nature are summarized briefly in Part II of the report. A list of recent publications of potential interest to the geothermal community and a directory of contributors to the geothermal progress monitoring system are also included.

Not Available

1982-06-01

128

Initial investigation of soil mercury geochemistry as an aid to drill site selection in geothermal systems  

Microsoft Academic Search

A mercury-in-soil survey was conducted at the Roosevelt Hot Springs Known Geothermal Resource Area (KGRA), Utah, to evaluate mercury soil geochemistry as a method of selecting exploration well sites in a hot-water geothermal system. Samples of -80 mesh soil were collected at 30.5 m intervals along traverses crossing known structures, surficial geothermal alteration, and exploration well sites, and were analyzed

R. M. Capuano; R. W. Bamford

1978-01-01

129

Design procedure for a greenhouse space heating system utilizing geothermal warm water  

Microsoft Academic Search

Tal, A., Segal, I., Regev, R., Steinfeld, A., Cohen, S. and Zer, I., 1987. Design procedure for a greenhouse space heating system utilizing geothermal warm water. Energy Agric., 6: 27-34. Utilization of warm geothermal water (40 ° -60 ° C) supplied from deep wells for heating of win- ter crops is being pursued in the Arava region of Israel. Systems

A. TAL; I. SEGAL; R. REGEV; A. STEINFELD; S. COHEN; I ZER

1987-01-01

130

Simulation of water–rock interaction in the Yellowstone geothermal system using TOUGHREACT  

Microsoft Academic Search

The Yellowstone geothermal system provides an ideal opportunity to test the ability of reactive transport models to simulate the chemical and hydrological effects of water–rock interaction. Previous studies of the Yellowstone geothermal system have characterized water–rock interaction through analysis of rocks and fluids obtained from both surface and downhole samples. Fluid chemistry, rock mineralogy, permeability, porosity, and thermal data obtained

Patrick F Dobson; Sonia Salah; Nicolas Spycher; Eric L Sonnenthal

2004-01-01

131

Proceedings of a Topical Meeting On Small Scale Geothermal Power Plants and Geothermal Power Plant Projects  

SciTech Connect

These proceedings describe the workshop of the Topical Meeting on Small Scale Geothermal Power Plants and Geothermal Power Plant Projects. The projects covered include binary power plants, rotary separator, screw expander power plants, modular wellhead power plants, inflow turbines, and the EPRI hybrid power system. Active projects versus geothermal power projects were described. In addition, a simple approach to estimating effects of fluid deliverability on geothermal power cost is described starting on page 119. (DJE-2005)

None

1986-02-12

132

[Geothermal system temperature-depth database and model for data analysis]. 4. quarterly technical progress report  

SciTech Connect

The activities that have been carried out this quarter include continued planning and development of the geothermal system thermal-well data-base that will be one of the main contract results. The authors are continuing to modify the specifications of the database and continuing initial input. They have added several additional areas to their inventory of the geothermal areas for which data are available in the literature (published and open file) and on open file as described in the third quarterly report. A map was enclosed with the second quarterly report that gave the preliminary location of sites of various categories of wells. They will include a revised map with the next quarterly report when all of the sites, including the new ones described below, have been located and added to the index map. In particular in the last quarter the authors have added about 100 wells in west Texas in the transPecos region from a previously proprietary report that they recently obtained. In addition they have made arrangements to obtain thermal data collected by AMAX Geothermal during their exploration activities. The number of wells is large, several hundred, and the sites are spread throughout the western US from New Mexico and Colorado to California and Oregon.

Blackwell, D.D.

1998-02-19

133

Implications of measured commercial building loads on geothermal system sizing  

SciTech Connect

This paper presents measured building load data from four commercial geothermal and water loop heat pump systems and discusses the implications for sizing ground loop heat exchangers. The four buildings include two Wisconsin office buildings with water loop heat pumps, a geothermal hotel in Upstate New York, and a geothermal high school in Eastern Tennessee. The buildings all use multiple heat pumps and range in size from 27,000 to 161,600 square feet (2,500 to 15,000 m{sup 2}). Monitored data at all four buildings were collected for more than 12 months. The data show that all buildings have significant amount of load diversity, with only 38% to 57% of the installed heat pumps operating simultaneously at peak cooling conditions. The high amount of diversity in the building loads implies that loop designs based on rules of thumb that consider the installed tonnage instead of the peak diversified or block loads will be oversized. The data from these buildings also confirm that cooling loads drive the loop sizing requirements, since the peak heat rejection loads were at least 70% greater than the heat extraction loads. The measured heat rejection loads on a peak, monthly and annual basis, normalized for floor area, were shown to be surprisingly similar despite the wide variation in the building application and geographic location. Peak heat rejection loads on a 4-hour basis ranged from 15 to 30 Btu/h-ft{sup 2} (550 to 1,110 W/m{sup 2}). Annual heat rejection loads for the offices and hotel ranged from 25,200 to 27,300 Btu/year-ft{sup 2} (286 to 310 MJ/year-m{sup 2}). At the high school, where cooling loads were light during the summer when classes were not in session, the annual heat rejection load was 14,800 Btu/year-ft{sup 2} (168 MJ/year-m{sup 2}).

Henderson, H.I. Jr.

1999-07-01

134

Development of geothermal logging systems in the United States  

SciTech Connect

Logging technologies developed for hydrocarbon resource evaluation have not migrated into geothermal applications even though data so obtained would strengthen reservoir characterization efforts. Two causative issues have impeded progress: (1) there is a general lack of vetted, high-temperature instrumentation, and (2) the interpretation of log data generated in a geothermal formation is in its infancy. Memory-logging tools provide a path around the first obstacle by providing quality data at a low cost. These tools feature on-board computers that process and store data, and newer systems may be programmed to make decisions. Since memory tools are completely self-contained, they are readily deployed using the slick line found on most drilling locations. They have proven to be rugged, and a minimum training program is required for operator personnel. Present tools measure properties such as temperature and pressure, and the development of noise, deviation, and fluid conductivity logs based on existing hardware is relatively easy. A more complex geochemical tool aimed at a quantitative analysis of (potassium, uranium and thorium) is in the calibration phase, and it is expandable into all nuclear measurements common in the hydrocarbon industry. A fluid sampling tool is in the design phase. All tools are designed for operation at conditions exceeding 400 C, and for deployment in the slim holes produced by mining-coring operations. Partnerships are being formed between the geothermal industry and scientific drilling programs to define and develop inversion algorithms relating raw tool data to more pertinent information. These cooperative efforts depend upon quality guidelines such as those under development within the international Ocean Drilling Program.

Lysne, P.

1994-04-01

135

A geochemical reconnaissance of the Alid volcanic center and geothermal system, Danakil depression, Eritrea  

USGS Publications Warehouse

Geological and geochemical studies indicate that a high-temperature geothermal system underlies the Alid volcanic center in the northern Danakil depression of Eritrea. Alid is a very late-Pleistocene structural dome formed by shallow intrusion of rhyolitic magma, some of which vented as lavas and pyroclastic flows. Fumaroles and boiling pools distributed widely over an area of ~10 km2 on the northern half of Alid suggest that an active hydrothermal system underlies much of that part of the mountain. Geothermometers indicate that the fumarolic gases are derived from a geothermal system with temperatures >225??C. The isotopic composition of condensed fumarolic steam is consistent with these temperatures and implies that the source water is derived primarily from either lowland meteoric waters or fossil Red Sea water, or both. Some gases vented from the system (CO2, H2S and He) are largely magmatic in origin. Permeability beneath the volcanic center may be high, given the amount of intrusion-related deformation and the active normal faulting within the Danakil depression.Geological and geochemical studies indicate that a high-temperature geothermal system underlies the Alid volcanic center in the northern Danakil depression of Eritrea. Alid is a very late-Pleistocene structural dome formed by shallow intrusion of rhyolitic magma, some of which vented as lavas and pyroclastic flows. Fumaroles and boiling pools distributed widely over an area of approx. 10 km2 on the northern half of Alid suggest that an active hydrothermal system underlies much of that part of the mountain. Geothermometers indicate that the fumarolic gases are derived from a geothermal system with temperatures >225??C. The isotopic composition of condensed fumarolic steam is consistent with these temperatures and implies that the source water is derived primarily from either lowland meteoric waters or fossil Red Sea water, or both. Some gases vented from the system (CO2, H2S and He) are largely magmatic in origin. Permeability beneath the volcanic center may be high, given the amount of intrusion-related deformation and the active normal faulting within the Danakil depression.

Lowenstern, J. B.; Janik, C. J.; Fournier, R. O.; Tesfai, T.; Duffield, W. A.; Clynne, M. A.; Smith, J. G.; Woldegiorgis, L.; Weldemariam, K.; Kahsai, G.

1999-01-01

136

Summary of geothermal exploration activity in the State of Washington from 1978 to 1983. Final report  

SciTech Connect

Project activity is summarized with references to the publications produced. Project findings are reported as they relate to specific geothermal resource target areas. Some major projects of the goethermal exploration program are: thermal and mineral spring chemistry, heat flow drilling, temperature gradient measurements, Cascade Range regional gravity, geohydrology study of the Yakima area, low temperature geothermal resources, geology, geochemistry of Cascade Mountains volcanic rocks, and soil mercury studies. (MHR)

Korosec, M.A.

1984-01-01

137

Gravity and magnetic features and their relationship to the geothermal system in southwestern South Dakota  

SciTech Connect

An attempt is made to determine the sources that are responsible for producing geothermal anomalies observed within the southern Black Hills region. Lithologic and structural boundaries residing in the upper crust and their relationship to the geothermal system are discussed. A regional gravity survey was supplemented by a regional aeromagnetic survey.

Hildenbrand, T.G.; Kucks, R.P.

1981-01-01

138

Technical and cost analysis of rock-melting systems for producing geothermal wells. [GEOWELL  

Microsoft Academic Search

The drilling of wells makes up a large fraction of the costs of geothermal energy-extraction plants, and billions of dollars for wells will be needed before geothermal energy is nationally significant. Technical and economic systems studies are summarized regarding the application of the Subterrene concept, i.e., excavating and penetrating rocks or soils by melting, to the production of deep wells

Altseimer

1976-01-01

139

Floating power optimization studies for the cooling system of a geothermal power plant  

Microsoft Academic Search

The floating power concept was studied for a geothermal power plant as a method of increasing the plant efficiency and decreasing the cost of geothermal power. The stored cooling concept was studied as a method of reducing the power fluctuations of the floating power concept. Parametric and optimization studies were conducted for a variety of different types of cooling systems

C. J. Shaffer

1977-01-01

140

Laboratory testing and modeling to evaluate perfluorocarbon compounds as tracers in geothermal systems  

SciTech Connect

The thermal stability and adsorption characteristics of three perfluorinated hydrocarbon compounds were evaluated under geothermal conditions to determine the potential to use these compounds as conservative or thermally-degrading tracers in Engineered (or Enhanced) Geothermal Systems (EGS). The three compounds tested were perfluorodimethyl-cyclobutane (PDCB), perfluoromethylcyclohexane (PMCH), and perfluorotrimethylcyclohexane (PTCH), which are collectively referred to as perfluorinated tracers, or PFTs. Two sets of duplicate tests were conducted in batch mode in gold-bag reactors, with one pair of reactors charged with a synthetic geothermal brine containing the PFTs and a second pair was charged with the brine-PFT mixture plus a mineral assemblage chosen to be representative of activated fractures in an EGS reservoir. A fifth reactor was charged with deionized water containing the three PFTs. The experiments were conducted at {approx}100 bar, with temperatures ranging from 230 C to 300 C. Semi-analytical and numerical modeling was also conducted to show how the PFTs could be used in conjunction with other tracers to interrogate surface area to volume ratios and temperature profiles in EGS reservoirs. Both single-well and cross-hole tracer tests are simulated to illustrate how different suites of tracers could be used to accomplish these objectives. The single-well tests are especially attractive for EGS applications because they allow the effectiveness of a stimulation to be evaluated without drilling a second well.

Reimus, Paul W [Los Alamos National Laboratory

2011-01-21

141

The application of unmanned aerial systems (UAS) in geophysical investigations of geothermal systems  

NASA Astrophysics Data System (ADS)

Investigations of geothermal systems typically involve ground-based geological and geophysical studies in order to map structures that control and facilitate fluid flow. The spatial extent of ground-based investigations can be limited, however, by surficial hot springs, dense foliage, and roadless or private lands. This can result in data gaps in key areas, particularly around active hydrothermal springs. Manned aircraft can provide access to these areas and can yield broad and uniform data coverage, but high-resolution surveys are costly and relatively inflexible to changes in the survey specifications that may arise as data are collected. Unmanned aerial systems (UAS) are well suited for conducting these surveys, but until recently, various factors (scientific instrumentation requirements, platform limitations, and size of the survey area) have required the use of large UAS platforms, rendering unmanned aerial surveys unsuitable for most investigations. We have developed and tested a new cesium magnetometer system to collect magnetic data using two different small-platform UAS that overcomes many of the challenges described above. We are deploying this new system in Surprise Valley, CA, to study the area's active geothermal field. Surprise Valley is ideally suited to testing UAS due to its low population density, accessible airspace, and broad playa that provides ample opportunity to safely land the aircraft. In combination with gravity and topographic data, magnetic data are particularly useful for identifying buried, intra-basin structures, especially in areas such as Surprise Valley where highly magnetic, dense mafic volcanic rocks are interbedded with and faulted against less magnetic, less dense sedimentary rock. While high-resolution gravity data must be collected at point locations on the ground, high-resolution magnetic data can be obtained by UAS that provide continuous coverage. Once acquired, the magnetic data obtained by the UAS will be combined with high-resolution airborne lidar data in order to correlate subsurface structures with subtle surface features, to identify possible conduits for, or barriers to, geothermal fluid circulation. Our September 2012 mission will deploy NASA's SIERRA UAS platform to perform a reconnaissance survey of the entire valley. Results from ground and flight tests indicate that magnetic "noise" from the SIERRA platform is low, and can be effectively compensated to provide data comparable with high-resolution commercial methods. A second mission will be flown in summer 2013 using the SWIFT platform, which will analyze data from its onboard sensors to continuously optimize its flight path in real-time to autonomously investigate regions of interest such as steep magnetic gradients or abrupt changes in anomaly amplitudes and wavelengths. The SWIFT also has the advantage that it can be flown as a glider, further reducing magnetic noise of the platform arising from the engine. This innovative use of UAS and intelligent automation in geophysical investigations offers the ability to obtain higher-resolution and more comprehensive and targeted data at a lower cost than is presently possible, expanding our ability to explore a wide variety of geothermal systems.

Glen, J. M.; Egger, A. E.; Ippolito, C.; Phelps, G. A.; Berthold, R.; Lee, R.; Spritzer, J. M.; Tchernychev, M.

2012-12-01

142

Geochemical exploration of a promissory Enhanced Geothermal System (EGS): the Acoculco caldera, Mexico.  

NASA Astrophysics Data System (ADS)

The Acoculco caldera (Puebla, Mexico) has been identified by the Mexican Federal Electricity Company (in Spanish 'Comisión Federal de Electricidad', CFE) as a potential Enhanced Geothermal System (EGS) candidate. Two exploration wells were drilled and promising temperatures of ~300° C have been measured at a depth of 2000 m with a geothermal gradient of 11oC/100m, which is three times higher than the baseline gradient measured within the Trans-Mexican Volcanic Belt. As usually observed in Hot Dry Rock systems, thermal manifestations in surface are scarce and consist in low-temperature bubbling springs and soil degassing. The goals of this study were to identify the origin of these fluids, to estimate the soil degassing rate and to explore new areas for a future detailed exploration and drilling activities. Water and gas samples were collected for chemical and isotopic analysis (?18O, ?D, 3He/4He, 13C, 15N) and a multi-gas (CO2, CH4, H2S) soil survey was carried out using the accumulation chamber method. Springs' compositions indicate a meteoric origin and the dissolution of CO2 and H2S-rich gases, while gas compositions reveal a MORB-type origin mixed with some arc-type contribution. Gas geothermometry results are similar to temperatures measured during well drilling (260° C-300° C). Amongst all measured CO2 fluxes, only 5% (mean: 5543 g m-2 day-1) show typical geothermal values, while the remaining fluxes are low and correspond to biogenic degassing (mean: 18 g m-2 day-1). The low degassing rate of the geothermal system is a consequence of the intense hydrothermal alteration observed in the upper 800 m of the system which acts as an impermeable caprock. Highest measured CO2 fluxes (above > 600 g m-2 day-1) have corresponding CH4/CO2 flux ratios similar to mass ratios of sampled gases, which suggest an advective fluid transport. To represent field conditions, a numerical model was also applied to simulate the migration of CO2 towards the surface through a shallow aquifer under fully saturated conditions. By changing some of the aquifer properties (i.e., depth, permeability and porosity), it was found how geothermal CO2 fluxes can show values similar to a biogenic background flux. Future field work at Acoculco will include ?13C analysis together with soil flux measurements for a better discrimination of the degassing origin, and a thinner flux measurement grid will be defined for a better detection of any possible gas flux anomaly.

Peiffer, Loic; Romero, Ruben Bernard; Pérez-Zarate, Daniel; Guevara, Mirna; Santoyo Gutiérrez, Edgar

2014-05-01

143

Thermal and chemical evolution of The Geysers geothermal system, California  

SciTech Connect

Fluid inclusions and mineral assemblages provide a reward of the thermal and chemical changes that occurred during the evolution of The Geysers geothermal system. The data document the presence of an extensive liquid dominated geothermal system that developed in response to felsite intrusion and its evolution to a vapor-dominated regime. Temperatures within the early liquid-dominated system ranged from 175 C at a distance of 7200 feet from the felsite to more than 350 C near the contact while salinities varied from 5 equivalent weight percent NaCl (at a distance of 5500 feet) to more than 26 weight percent NaCl. As temperatures around the felsite declined, the liquid-dominated system collapsed upon itself. Downward migration of the low salinity waters resulted in dilution of the fluids present in regions now occupied by the caprock and normal vapor-dominated reservoir. In contrast, dilution was minor in rocks now hosting the high-temperature vapor-dominated reservoir. This suggests that low permeabilities are the primary reason for the development of the high-temperature reservoir. Boiling within the caprock produced late-stage veins of calcite and quartz. As the fluid boiled off, condensate was trapped as low salinity fluid inclusions. Within the main body of the reservoir, a liquid phase with salinities of up to 7 equivalent weight percent NaCl persisted to temperatures between 250 and 270 C. However, except for the presence of vapor-rich inclusions, little evidence of boiling within the reservoir rocks was preserved.

Moore, J.N.

1992-01-01

144

High Fluoride and Geothermal Activities In Continental Rift Zones, Ethiopia  

NASA Astrophysics Data System (ADS)

The Central Main Ethiopian Rift basin is a continental rift system characterized by volcano-tectonic depression endowed with huge geothermal resource and associated natural geochemical changes on groundwater quality. Chemical composition of groundwater in the study area showed a well defined trend along flow from the highland and escarpment to the rift floor aquifer. The low TDS (< 500mg/l) Ca-Mg-HCO3 dominated water at recharge area in the highlands and escarpments evolve progressively into Ca-Na-HCO3 and Na-Ca-HCO3 type waters along the rift ward groundwater flow paths. These waters finally appear as moderate TDS (mean 960mg/l) Na-HCO3 type and as high TDS (> 1000 mg/l) Na-HCO3-Cl type in volcano-lacustrine aquifers of the rift floor. High concentrations of fluoride (up to 97.2 mg/l) and arsenic (up to 98?g/l) are recognized feature of groundwaters which occur mostly in the vicinity of the geothermal fields and the rift lakes in the basin. Fluoride and arsenic content of dry volcaniclastic sediments close to these areas are in the range 666-2586mg/kg and 10-13mg/kg respectively. The relationship between fluoride and calcium concentrations in groundwaters showed negative correlation. Near-equilibrium state attained between the mineral fluorite (CaF2) and the majority of fluoride-rich (>30mg/l) thermal groundwater and shallow cold groundwater. This indicated that the equilibrium condition control the high concentration of fluoride in the groundwaters. Whereas undersaturation state of fluorite in some relatively low-fluoride (<30mg/l) thermal waters indicated a dilution by cold waters. Laboratory batch leaching experiments showed that fast dissolution of fluoride from the sediment samples suddenly leached into the interacting water at the first one hour and then remain stable throughout the experiment. The concentrations of leached fluoride from the hot spring deposits, the lacustrine sediments, and the pyroclastic rock are usually low (1% of the total or less than the content in the sediment or rock) but strongly correlated with the concentrations in groundwaters in the local vicinity. The readily leachable hot spring deposits and local lacustrine sediments, which were leached easily as high as three fold of other sediments leachability, are considered as the reservoir for the potential fluoride contamination of the rift groundwater. Leaching of fluoride in the sub-surface system is simulated with sediment-packed column leached by flowing water and applying temporary interruption of flow during the experiment. The result indicated that a sharp increase of fluoride concentration (up to 58mg/kg) observed in leachates before one pore-volume of water eluted from the column. The concentration of leached fluoride consequently declined with the increased flowing pore-volume of water and finally the lowest concentrations of leached fluoride occurred in the end of the experiment. Flow interruption during column leaching experiment causes a noticeable fluoride concentration perturbation due to the heterogeneity of the sediment.

Weldesenbet, S. F.; Wohnlich, S.

2012-12-01

145

Fluoride and Geothermal Activities In Continental Rift Zones, Ethiopia  

NASA Astrophysics Data System (ADS)

The Central Main Ethiopian Rift basin is a continental rift system characterized by volcano-tectonic depression endowed with huge geothermal resource and associated natural geochemical changes on groundwater quality. Chemical composition of groundwater in the study area showed a well defined trend along flow from the highland and escarpment to the rift floor aquifer. The low TDS (< 500mg/l) Ca-Mg-HCO3 dominated water at recharge area in the highlands and escarpments evolve progressively into Ca-Na-HCO3 and Na-Ca-HCO3 type waters along the rift ward groundwater flow paths. These waters finally appear as moderate TDS (mean 960mg/l) Na-HCO3 type and as high TDS (> 1000 mg/l) Na-HCO3-Cl type in volcano-lacustrine aquifers of the rift floor. High concentrations of fluoride (up to 97.2 mg/l) and arsenic (up to 98?g/l) are recognized feature of groundwaters which occur mostly in the vicinity of the geothermal fields and the rift lakes in the basin. Fluoride and arsenic content of dry volcaniclastic sediments close to these areas are in the range 666-2586mg/kg and 10-13mg/kg respectively. The relationship between fluoride and calcium concentrations in groundwaters showed negative correlation. Near-equilibrium state attained between the mineral fluorite (CaF2) and the majority of fluoride-rich (>30mg/l) thermal groundwater and shallow cold groundwater. This indicated that the equilibrium condition control the high concentration of fluoride in the groundwaters. Whereas undersaturation state of fluorite in some relatively low-fluoride (<30mg/l) thermal waters indicated a dilution by cold waters. Laboratory batch leaching experiments showed that fast dissolution of fluoride from the sediment samples suddenly leached into the interacting water at the first one hour and then remain stable throughout the experiment. The concentrations of leached fluoride from the hot spring deposits, the lacustrine sediments, and the pyroclastic rock are usually low (1% of the total or less than the content in the sediment or rock) but strongly correlated with the concentrations in groundwaters in the local vicinity. The readily leachable hot spring deposits and local lacustrine sediments, which were leached easily as high as three fold of other sediments leachability, are considered as the reservoir for the potential fluoride contamination of the rift groundwater. Leaching of fluoride in the sub-surface system is simulated with sediment-packed column leached by flowing water and applying temporary interruption of flow during the experiment. The result indicated that a sharp increase of fluoride concentration (up to 58mg/kg) observed in leachates before one pore-volume of water eluted from the column. The concentration of leached fluoride consequently declined with the increased flowing pore-volume of water and finally the lowest concentrations of leached fluoride occurred in the end of the experiment. Flow interruption during column leaching experiment causes a noticeable fluoride concentration perturbation due to the heterogeneity of the sediment.

Weldesenbet, S. F.

2012-12-01

146

Endolithic Phototrophs from an Active Geothermal Region in New Zealand  

Microsoft Academic Search

Endolithic photosynthetic communities in geothermal siliceous rocks in the area of Rotorua, New Zealand, were analysed using traditional microbiological and molecular biology techniques. Rock surface temperatures varied between 40°C and 60°C. Major endoliths included cyanobacteria of subsections I, II and V. Few subsection IV organisms were found and subsection III (filamentous, non-heterocystous) cyanobacteria were present only as epiliths or chasmoendoliths.

Peter Michael Gaylarde; Anne-Dorothee Jungblut; Christine Claire Gaylarde; Brett Anthony Neilan

2006-01-01

147

Low Temperature Geothermal Electricity Generation: Google Earth Virtual Field Trip Activity  

NSDL National Science Digital Library

This exploration takes students to Chena Hot Springs Resort in Alaska where they will learn how to produce low temperature geothermal electricity. Teacher's guide, activity sheet and PowerPoint presenation included. The 2008 ATEEC Fellows Institute brought 18 environmental science community college and high school instructors to Alaska. They created virtual field trips using Google Earth. In the activity, explore Chena Hot Springs Resort in Alaska to learn about low temperature geothermal electricity generation. Chena Hot Springs runs their entire facility on renewable energy. Learn how they do it why they do it and the engineering challenges along the way. This activity includes numerous turnkey teaching resources such as a PowerPoint presentation explaining the geothermal heat exchanging process, video interviews with environmental engineers, a teacher's guide and student activity. Users must create a free login to access this resource.

2013-06-06

148

Economic Analysis of Heating Systems using Geothermal Heat Pump  

Microsoft Academic Search

This paper presents profitability evaluation of geothermal heat pumps as an alternative, non-polluting solution for heating of modern buildings and well-insulated houses. The investment into geothermal heat pump is much higher than for heating stations with fossil fuels, more than four times as for earth gas and more than three times than for light fuel oil, but the operating costs

E. TORHAC; L. C. LIPUS; J. KROPE; D. GORICANEC; A. SALJNIKOV; R. STIPIC; Ð. KOZIC

149

Coniform stromatolites from geothermal systems, North Island, New Zealand  

USGS Publications Warehouse

Coniform stromatolites are found in several sites in the Tokaanu and Whakarewarewa geothermal areas of North Island, New Zealand. At Tokaanu, silicification of these stromatolites is taking place in Kirihoro, a shallow hot springfed pool. At Whakarewarewa, subfossil silicified coniform stromatolites are found on the floor of "Waikite Pool" on the discharge apron below Waikite Geyser, and in an old sinter succession at Te Anarata. The microbes in the coniform stromatolites from Tokaanu, Waikite Pool, and Te Anarata have been well preserved through rapid silicification. Nevertheless, subtle differences in the silicification style induced morphological variations that commonly mask or alter morphological features needed for identification of the microbes in terms of extant taxa. The coniform stromatolites in the New Zealand hotspring pools are distinctive because (1) they are formed of upward tapering (i.e., conical) columns, (2) neighboring columns commonly are linked by vertical sheets or bridges, (3) internally, they are formed of alternating high- and low-porosity laminae that have a conical vertical profile, and (4) Phormidium form more than 90% of the biota. As such, they are comparable to modern coniform mats and stromatolites found in the geothermal systems of Yellowstone National Park and ice-covered lakes in Antarctica. Formation of the coniform stromatolites is restricted to pools that are characterized by low current energy and a microflora that is dominated by Phormidium. These delicate and intricate stromatolites could not form in areas characterized by fast flowing water or a diverse microflora. Thus, it appears that the distribution of these distinctive stromatolites is controlled by biological constraints that are superimposed on environmental needs.

Jones, B.; Renaut, R. W.; Rosen, M. R.; Ansdell, K. M.

2002-01-01

150

Characterization of hot dry rock geothermal energy extraction systems  

NASA Astrophysics Data System (ADS)

The engineering of heat exchange systems by which geothermal heat can be efficiently extracted from hot impermeable rocks is studied. The system currently under investigation at Fenton Hill, New Mexico consists of a network of large fractures created through the hydraulic pressurization of a well penetrating hot basement rocks and subsequently intersected by a second well drilled to form a flow-thru system. Cool water pumped into the fractures through one well, once heated in the reservoir, returns to the surface through the second well, is cooled, and then recirculated. While much is known about the performance parameters of the fracture network from short-term flow tests, little is understood concerning the spatial dimensions and geometrical relationship of individual fractures comprising the network. Ultimately, the success one has in estimating the long-term performance of such a system where commercialization is an issue, and in engineering future systems with optimal performance, depends on the success in characterizing the flow-thru fracture networks.

Albright, J. N.; Newton, C. A.

1981-04-01

151

Local Magmatic Episodes and Heat Sources for Hydrothermal Activity in the Kawerau Geothermal Field, Taupo Volcanic Zone, New Zealand  

NASA Astrophysics Data System (ADS)

Kawerau Geothermal Field is the most northeasterly of the major, high-temperature geothermal fields in the central Taupo Volcanic Zone (TVZ, New Zealand), an intensely active Quaternary arc locus of rhyolitic volcanism and thermal output. Kawerau is situated at a transition where the voluminous silicic volcanism and associated magmatism of the central TVZ merge into the andesite-dacite dominated northern TVZ. Structurally, the Kawerau system lies within the southern part of the northeast-trending Whakatane Graben, in a zone where the active TVZ rift structures intersect the north-trending strike-slip faults of the North Island Shear Belt. The field is hosted in 600-1000 m of volcanic rocks and sediments overlying faulted Mesozoic basement greywacke. Fractured coherent rhyolite lava bodies occur between 0 and -1000 m below sea level, with several bodies intersected by drilling. These rhyolites represent local upper-crustal sources of magma, which could have provided heat input for past geothermal systems. Differentiating these rhyolites is important in deciphering the timing of past thermal events, and whether the modern field is long-lived or episodically rejuvenated. Age determinations obtained from samples of the rhyolite using single-crystal U-Pb dating on zircon (Secondary Ion Mass Spectrometry, using the SHRIMP-RG instrument) show the rhyolite bodies to belong to two periods of eruptive activity, one around 360 ka, the other around 140 ka. The older, more voluminous episode is represented by two petrographic magma types, each sampled as a buried surficial lava dome, and one or more buried intersections of sills. The younger episode is represented by modern surficial domes and by two intersections of dike feeders within the greywacke basement. Previous interpretations of the current Kawerau Geothermal Field as a long-lived system are now questioned, as it is apparent that only at long-spaced intervals is there evidence of magma at shallow enough crustal levels beneath the field to generate vigorous hydrothermal activity (as at the present day). The contrast between earlier sill emplacement and later diking is taken as reflecting a change in orientation of the principal stress axes at the field from ?3 vertical around 360 ka, to ?3 horizontal and orientated northwest-southeast (i.e., the modern TVZ orientation) by ca. 140 ka. The age data have provided key insights into the temporal evolution of rhyolitic magmatic activity at Kawerau, with the intrusive complexes representing past heat sources that have given rise to temporally discrete, geographically coincident 'Kawerau geothermal systems'.

Milicich, S. D.; Wilson, C. J.; Bignall, G.; Pezaro, B.

2012-12-01

152

Geothermal Energy.  

ERIC Educational Resources Information Center

This curriculum unit describes geothermal energy in the context of the world's energy needs. It addresses renewable and nonrenewable energy sources with an in-depth study of geothermal energy--its geology, its history, and its many uses. Included are integrated activities involving science, as well as math, social studies, and language arts.…

Nemzer, Marilyn; Page, Deborah

153

Faults and gravity anomalies over the East Mesa hydrothermal-geothermal system  

SciTech Connect

Detailed interpretations of gravity anomalies over geothermal systems may be extremely useful for mapping the fracture or fault systems that control the circulation of the thermal waters. This approach seems to be particularly applicable in areas like the Salton Trough where reactions between the thermal waters and the porous sediments produce authigenic-hydrothermal minerals in sufficient quantity to cause distinct gravity anomalies at the surface. A 3-D inversion of the residual Bouguer gravity anomaly over the East Mesa geothermal field was made to examine the densified volume of rock. We show that the data not only resolve a north-south and an intersecting northwest structure, but that it may be possible to distinguish between the active present-day hydrothermal system and an older and cooler part of the system. The densified region is compared spatially to self-potential, thermal and seismic results and we find a good concordance between the different geophysical data sets. Our results agree with previous studies that have indicated that the main feeder fault recharging the East Mesa reservoir dips steeply to the west.

Goldstein, N.E.; Carle, S.

1986-05-01

154

Method for inhibiting silica precipitation and scaling in geothermal flow systems  

DOEpatents

A method for inhibiting silica scaling and precipitation in geothermal flow systems by on-line injection of low concentrations of cationic nitrogen-containing compounds, particularly polymeric imines, polymeric amines, and quaternary ammonium compounds.

Harrar, Jackson E. (Castro Valley, CA); Lorensen, Lyman E. (Orinda, CA); Locke, Frank E. (Lafayette, CA)

1982-01-01

155

Method for inhibiting silica precipitation and scaling in geothermal flow systems  

DOEpatents

A method for inhibiting silica scaling and precipitation in geothermal flow systems by on-line injection of low concentrations of cationic nitrogen-containing compounds, particularly polymeric imines, polymeric amines, and quaternary ammonium compounds is described.

Harrar, J.E.; Lorensen, L.E.; Locke, F.E.

1980-06-13

156

Design, fabrication, delivery, operation and maintenance of a geothermal power conversion system  

NASA Technical Reports Server (NTRS)

The design, fabrication, delivery, operation and maintenance of an Hydrothermal Power Company 1250 KVA geothermal power conversion system using a helical screw expander as the prime mover is described. Hydrostatic and acceptance testing are discussed.

1980-01-01

157

Helium isotopes in geothermal systems: Iceland, The Geysers, Raft River and Steamboat Springs  

NASA Astrophysics Data System (ADS)

Helium isotope ratios have been measured in geothermal fluids from Iceland, The Geysers, Raft River, Steamboat Springs and Hawaii. These ratios have been interpreted in terms of the processes which supply He in distinct isotopic ratios ( i.e. magmatic He, ~10 R a; atmospheric He, R a; and crustal He, ~0.1 R a) and in terms of the processes which can alter the isotopic ratio (hydrologic mixing, U-Th series alpha production and weathering release of crustal He, magma aging and tritiugenic addition of 3He). Using this interpretational scheme, Iceland is found to be an area of hot-spot magmatic He implying an active volcanic source although the data are suggestive of high-temperature weathering release of crustal He incorporated in the geothermal fluids. By comparison to fumarolic gases from Hawaii and Juan De Fuca and Cayman Trench basaltic glass samples, The Geysers contains MOR type magmatic He again implying an active volcanic source possibly a "leaky" transform related to the San Andreas Fault System. Raft River contains only crustal He indicating no active volcanic sources. Steamboat Springs He isotope ratios are distinctly less than typical plate margin volcanics but must still have a magmatic source. A preliminary assessment of the cause for this low ratio is made assuming an "aging" magma source.

Torgersen, T.; Jenkins, W. J.

1982-05-01

158

Geothermal Reservoir Dynamics - TOUGHREACT  

SciTech Connect

This project has been active for several years and has focused on developing, enhancing and applying mathematical modeling capabilities for fractured geothermal systems. The emphasis of our work has recently shifted towards enhanced geothermal systems (EGS) and hot dry rock (HDR), and FY05 is the first year that the DOE-AOP actually lists this project under Enhanced Geothermal Systems. Our overall purpose is to develop new engineering tools and a better understanding of the coupling between fluid flow, heat transfer, chemical reactions, and rock-mechanical deformation, to demonstrate new EGS technology through field applications, and to make technical information and computer programs available for field applications. The objectives of this project are to: (1) Improve fundamental understanding and engineering methods for geothermal systems, primarily focusing on EGS and HDR systems and on critical issues in geothermal systems that are difficult to produce. (2) Improve techniques for characterizing reservoir conditions and processes through new modeling and monitoring techniques based on ''active'' tracers and coupled processes. (3) Improve techniques for targeting injection towards specific engineering objectives, including maintaining and controlling injectivity, controlling non-condensable and corrosive gases, avoiding scale formation, and optimizing energy recovery. Seek opportunities for field testing and applying new technologies, and work with industrial partners and other research organizations.

Pruess, Karsten; Xu, Tianfu; Shan, Chao; Zhang, Yingqi; Wu,Yu-Shu; Sonnenthal, Eric; Spycher, Nicolas; Rutqvist, Jonny; Zhang,Guoxiang; Kennedy, Mack

2005-03-15

159

Geochemical characterizationof geothermal systems in the Great Basin: Implications for exploration exploitation and environmental issues  

Microsoft Academic Search

Abstract ,The objective of this ongoing ,project is the development ,of a representative geochemical database for a comprehensive range of elemental and isotopic parameters (i.e., beyond the typical data suite) for a range of geothermal systems in the Great Basin. Development,of this database is one of the first steps in understanding the nature of geothermal,systems in the Great Basin. Of

Greg B. Arehart; Mark F. Coolbaugh; Simon R. Poulson

160

The origin of high-temperature zones in vapor-dominated geothermal systems  

SciTech Connect

Vapor-dominated geothermal systems are proposed to originate by downward extension (by the ''heat pipe'' mechanism) into hot dry fractured rock above a large cooling igneous intrusion. High temperature zones found by drilling are shallow parts of the original hot dry rock where the penetration of the vapor reservoir was limited, and hot dry rock may extend under much of these reservoirs. An earlier hot water geothermal system may have formed during an early phase of the heating episode.

Truesdell, Alfred H.

1991-01-01

161

Simulation of water-rock interaction in the yellowstone geothermal system using TOUGHREACT  

Microsoft Academic Search

The Yellowstone geothermal system provides an ideal opportunity to test the ability of reactive transport models to accurately simulate water-rock interaction. Previous studies of the Yellowstone geothermal system have characterized water-rock interaction through analysis of rocks and fluids obtained from both surface and downhole samples. Fluid chemistry, rock mineralogy, permeability, porosity, and thermal data obtained from the Y-8 borehole in

Patrick F. Dobson; Sonia Salah; Nicolas Spycher; Eric L. Sonnenthal

2003-01-01

162

Geothermics and the deep flow-system of the Hungarian Basin  

NASA Astrophysics Data System (ADS)

The Hungarian Basin is a large depression. The deep multilayer flow-system of this basin represents a thermal circulation in equilibrium under natural conditions. The terrestrial heat-flow of the basin can be considered balanced, therefore, any geothermal anomaly is of convective origin. Negative geothermal anomaly and low salinity of the water characterize the recharge area and positive anomaly and high salinity the discharge belt. All is proved by geothermal, hydrochemical and hydrodynamic maps of the thermal water aquifer. Deep flow through thick and highly permeable deposits of the main recharge area cause strong negative anomaly and very low salinity. Extreme anomalies are of tectonic origin.

Erdélyi, M.

1985-12-01

163

Enhanced Geothermal System Development of the AmeriCulture Leasehold in the Animas Valley  

SciTech Connect

Working under the grant with AmeriCulture, Inc., and its team of geothermal experts, assembled a plan to apply enhanced geothermal systems (EGS) techniques to increase both the temperature and flow rate of the geothermal waters on its leasehold. AmeriCulture operates a commercial aquaculture facility that will benefit from the larger quantities of thermal energy and low cost electric power that EGS technology can provide. The project brought together a team of specialists that, as a group, provided the full range of expertise required to successfully develop and implement the project.

Duchane, David V; Seawright, Gary L; Sewright, Damon E; Brown, Don; Witcher, James c.; Nichols, Kenneth E.

2001-03-02

164

Multi-Use Geothermal Energy System with Augmentation for Enhanced Utilization. Non-Electric Application of Geothermal Energy in Susanville, California. Final Report.  

National Technical Information Service (NTIS)

Aeroject Energy Conversion Company has completed a site specific engineering and economic study of multi-use, augmented geothermal space/water heating and cooling systems in cooperation with the City of Susanville, California. The overall benefits to the ...

G. K. Olsonn D. L. Benner-Drury G. R. Cunnington

1979-01-01

165

Magnetotelluric results from the Ohaaki Geothermal System, Taupo Volcanic Zone, New Zealand  

NASA Astrophysics Data System (ADS)

The Ohaaki geothermal system in the Taupo Volcanic Zone currently supports a 100 MW power station and has long history of geophysical investigation using electrical methods since its first delineation by DC resistivity mapping. Although the shallow (<1 km) resistivity structure is well known from detailed DC resistivity mapping using long-wire Schlumbeger resistivity surveys and from long-offset tensor bipole-dipole surveys little is know about the deep structure of geothermal system below the deepest wells, ~ 3km. At these depths the geothermal reservoir is contained in the meta-sedimentary basement rocks (greywackes) which have very poor permeability. Magnetotelluric (MT) studies at the Rotokawa geothermal field about 15 km to the southwest, suggest that the deep high temperature part of the geothermal system (also hosted in greywacke) is anomalously resistive. Here we report the findings from a 20 km long profile of 28 broad-band MT measurement stations through the centre of the Ohaaki geothermal system. Although the near-surface low-resistivity anomaly marking the Ohaaki system is a 3-D feature, phase tensor analysis of the MT data show that at longer periods the MT response is quasi 2-D. 2-D inverse modelling of the MT data identify a narrow (~600 m) near vertical (dyke-like) zone of high conductivity on the south-eastern side of the geothermal field. The geochemistry of the gas from samples taken from this side of the geothermal field have a distinct volcanic signature suggesting that we may be imaging the source of these volcanic gases.

Hill, G. J.; Caldwell, T. G.; Bennie, S.; Heise, W.; Mroczek, E.; Bignall, G.

2009-12-01

166

Geothermal drilling research in the United States  

SciTech Connect

The high cost of drilling and completing geothermal wells is an impediment to the development of this resource. The Department of Energy (DOE), Division of Geothermal Energy (DGE), is conducting an R and D program directed at reducing well costs through improvements in geothermal drilling and completion technology. This program includes R and D activities in high temperature drilling hardware, drilling fluids, lost circulation control methods, completion technology, and advanced drilling systems. An overview of the program is presented.

Varnado, S.G.; Maish, A.B.

1980-01-01

167

Application of the U.S. Geoscience Information Network to deploying a National Geothermal Data System  

NASA Astrophysics Data System (ADS)

A coalition of State Geological Surveys is expanding and enhancing the National Geothermal Data System (NGDS, www.geothermaldata.org) by creating a national, sustainable, distributed, interoperable network of data providers representing all 50 states that will develop, collect, serve, and maintain geothermal-relevant data that operates as an integral compliant component of NGDS. The data exchange mechanism is built on the U.S. Geoscience Information Network (USGIN) protocols and standards (http://usgin.org, http://lab.usgin.org). Data are exposed from the State Geological Surveys through the NGDS, by digitizing at-risk legacy, geothermal-relevant data (paper records, samples, etc), publishing existing digital data using standard web and data services, and through limited collection of new data in areas lacking critical information. Goals are to enhance states' abilities to preserve and disseminate geothermal data; facilitate geothermal resource characterization and development efforts; expand the scope of data available to the geothermal community; foster new services and applications built by third-parties to take advantage of the system’s capabilities and content; contribute materially to creation of a national geoinformatics system through implementation and deployment of NGDS; and increase operational support for geoinformatics infrastructure through a broader user base.

Allison, M. L.; Richard, S. M.; Clark, R. J.; Grunberg, W.

2010-12-01

168

Applicability of `GREATEM' system in mapping geothermal regions in volcanic areas  

NASA Astrophysics Data System (ADS)

The ‘GREATEM’ helicopter borne TEM system employs a long grounded cable as transmitter while a light weight receiver coil is flown below a helicopter. This arrangement greatly simplifies the flying logistics and speed of the survey. Also there is very little reduction in the anomaly amplitude when the survey altitude is increased. This is a great advantage particularly in volcanic regions usually having rough topography, as the ‘GREATEM’ survey can be done with helicopter flying at a safe height. Many volcanic areas have anomalous geothermal regions containing hydrothermal fluids. Eruption of volcanoes may cause changes in the thermal character and spatial distribution of these regions. Mapping of these regions is important as they may be associated with hazards. Sometimes, if the temperature is high and volume of the geothermal region is large, they can provide a good source of geothermal energy. Applicability of ‘GREATEM’ system in mapping geothermal regions in volcanic areas is studied by numerical modeling. We have considered a 3D conductor at a shallow depth (50 t0 100m), representing the anomalous geothermal region with dimensions of 500m X 500m X 500m. Different types of geological host environment are considered by varying their resistivities from 10 Ohm.m to 2000 Ohm.m. The ‘GREATEM’ response is analyzed as ‘Percentage Difference (PD)’ over the response produced by the host environment. It is found that the “GREATEM’ system can delineate the geothermal region well. Many geothermal regions are associated with a deeper (> 1 km) reservoir of much larger dimensions. In this situation also it is found that the ‘GREATEM’ system can pick up the response of the shallower geothermal region against the background response of different types of geological host environment containing the deeper reservoir (Figure 1).

Verma, S. K.; Mogi, T.; Abd Allah, S.

2010-12-01

169

Wind energy/geothermic/solar heating system. Final report  

SciTech Connect

I've observed three distinct ''camps'' of renewable energy resources; WIND, Geothermic, and Solar. None of the three are completely adequate for the NE by themselves. I observe little effort to combine them to date. My objective has been to demonstrate that the three can be combined in a practical system. To mitagate the high cost and poor payback for individual residences, I believe neighborhoods of 4 to 5 homes, apartment complexes or condominiums could form an Energy Association alloting a piece of ground (could be a greenbelt) which would contain the well or wells, solar boosted underground water storage and the Solar banks. These are the high cost items which could be prorated and ammortized by the Association. Easements would permit each residence underground insulated water lines for individual heat pump conversions to existing forced air furnaces. Where regulations permit, an individual home could erect his own windmill to belt drive his freon compressor. With or without the optional windmill the water to freon heat pump with its solar boosts on the well water, will enjoy COP's (coefficient of Performances or times better than electric resistance heat) beyond anything on the market today. In a neighborhood energy association, all trenching could be done together all plumbing could be one contract and they could qualify for quantity discounts on heat pump units, chillers and components and installation.

Not Available

1981-01-01

170

Preliminary assessment of the geothermal system of the Tiris volcanic area, East Java, Indonesia.  

NASA Astrophysics Data System (ADS)

Indonesia, with 15 % of the world's active volcanoes, hosts a total estimated geothermal potential of 27000 MW of which 1197 MWe in 2011 have been installed. Exploration of magmatic remote areas is therefore important. Our investigation area is located at the volcano Lamongan, Tiris East Java, Indonesia, which is part of the modern Sunda Arc Region, characterized by extensional regime. The average ground water temperature in the area ranges between 27 and 29 ° C and the warm springs between 35 - 45 ° C, evidencing a geothermal potential of the area. Numerous maars and cindered cones have been located and studied here, some of them with a NW - SE lineament similar to the Tiris fault (only observed in satellite images). In this first exploration stage we characterized the geochemistry of the springs and investigated the petrology of the rocks. They were analyzed in terms of mineral composition (optical microscopy and electron microprobe) and major element composition (X-ray fluorescence). The samples have a typical basaltic - basaltic andesite composition, with abundant plagioclase with An65 up to An90, as well as olivine and pyroxene. The plagioclase crystals are several mm large, twinned and show no hydrothermal alteration. The fluid chemistry was determined in term of cation and anion concentration with Inductively Coupled Plasma Mass Spectrometry. The chemistry of geothermal waters provides specific information about the deep of the fluids in geothermal system and the discharge location. The concentrations of Na+, Ca2+, Li+, B3+ and Cl- suggest that the water of the Lamongan area derive from sea water intrusions. The high permeable pyroclastites, overlain by lower permeable basalt - andesitic basalt, observed in the field, may have channeled the sea water from the coast to the Tiris area. A structural lineament, NW - SE, may control the water intrusion, as the lineament of the springs confirms. The high HCO3-concentration in the fluid samples, as no carbonate rocks are known in the area, must derive from another source (magma chamber?). The occurrence of pyroclastites overlain by andesite suggests the presence of a concealed layer. This could be responsible for capturing SO42- accounting to the HCO3- excess of the springs, located in the outflow zone of the system. Acknowledgements We thank the German Federal Ministry for Education and Research (BMBF) for funding this German project under the grant 03G0753A. We would also like to thank Iris Pieper for the ICP water analyses at the TU Berlin, and DINAS ESDM, Surabaya, Indonesia for their support in the field campaigns.

Deon, F.; Moeck, I.; Sheytt, T.; Jaya, M. S.

2012-04-01

171

Support of US Geothermal Industry.  

National Technical Information Service (NTIS)

Geothermal Energy Association supports the US geothermal industry in its efforts to bring more clean geothermal energy on-line throughout the world. Activities designed to accomplish this goal include: (1) developing and maintaining data bases, web pages,...

K. Gawell

2004-01-01

172

Development of a Deep-Penetrating, Compact Geothermal Heat Flow System for Robotic Lunar Geophysical Missions  

NASA Technical Reports Server (NTRS)

Geothermal heat flow measurements are a high priority for the future lunar geophysical network missions recommended by the latest Decadal Survey of the National Academy. Geothermal heat flow is obtained as a product of two separate measurements of geothermal gradient and thermal conductivity of the regolith/soil interval penetrated by the instrument. The Apollo 15 and 17 astronauts deployed their heat flow probes down to 1.4-m and 2.3-m depths, respectively, using a rotary-percussive drill. However, recent studies show that the heat flow instrument for a lunar mission should be capable of excavating a 3-m deep hole to avoid the effect of potential long-term changes of the surface thermal environment. For a future robotic geophysical mission, a system that utilizes a rotary/percussive drill would far exceed the limited payload and power capacities of the lander/rover. Therefore, we are currently developing a more compact heat flow system that is capable of 3-m penetration. Because the grains of lunar regolith are cohesive and densely packed, the previously proposed lightweight, internal hammering systems (the so-called moles ) are not likely to achieve the desired deep penetration. The excavation system for our new heat flow instrumentation utilizes a stem which winds out of a pneumatically driven reel and pushes its conical tip into the regolith. Simultaneously, gas jets, emitted from the cone tip, loosen and blow away the soil. Lab tests have demonstrated that this proboscis system has much greater excavation capability than a mole-based heat flow system, while it weighs about the same. Thermal sensors are attached along the stem and at the tip of the penetrating cone. Thermal conductivity is measured at the cone tip with a short (1- to 1.5-cm long) needle sensor containing a resistance temperature detector (RTD) and a heater wire. When it is inserted into the soil, the heater is activated. Thermal conductivity of the soil is obtained from the rate of temperature increase during the heating. By stopping during the excavation, it is possible to measure thermal conductivities at different depths. The gas jets are turned off when the penetrating cone reaches the target depth. Then, the stem pushes the needle sensor into the undisturbed soil at the bottom of the hole and carries out a thermal conductivity measurement. When the measurement is complete, the system resumes excavation. RTDs, placed along the stem at short (approx 30 cm) intervals, will monitor long-term temperature stability of the subsurface. Temperature in the shallow subsurface would fluctuate with the diurnal, annual, and precession cycles of the Moon. These thermal waves penetrate to different depths into the regolith. Longterm monitoring of the subsurface temperature would allow us to accurately delineate these cyclic signals and separate them from the signal associated with the outward flow of the Moon s endogenic heat. Further, temperature toward bottom of the 3-m hole should be fairly stable after the heat generated during the excavation dissipates into the surrounding soil. The geothermal gradient may be determined reliably from temperature measurements at the RTDs near the bottom. In order to minimize the heat conduction along the stem from affecting the geothermal gradient measurements, we plan to use low-conductive materials for the stem and develop a mechanism to achieve close coupling between the RTDs and the wall of the excavated hole.

Nagihara, Seiichi; Zacny, Kris; Hedlund, Magnus; Taylor, Patrick T.

2012-01-01

173

The volcanic and geothermally active Campi Flegrei caldera: an integrated multidisciplinary image of its buried structure  

NASA Astrophysics Data System (ADS)

The Campi Flegrei caldera in southern Italy is one of the greatest geohazard areas on Earth. Evidence of an active magmatic and geothermal system is provided by ongoing ground uplift, with volcano-tectonic and long-period (LP) seismicity, the persistent degassing of ~1500 tonnes of CO2 per day, the presence of hot fumaroles at temperatures of 90-150 °C, brine-rich aquifers (with total dissolved solids up to 33 g l-1) and high thermal gradients in the crust (with temperatures reaching 420 °C at 3,050 m b.s.l.). Since the 1940s, more than 100 exploratory boreholes have been drilled in the area to depths of 80-3,100 m by the Azienda Geologica Italiana Petroli (AGIP) and the Società Anonima Forze Endogene Napoletane (SAFEN). To date, however, no systematic reanalysis of the drilling data has been carried out, and the buried volcanic structure has not been updated using the most recent scientific results and previous findings. By integrating unpublished data from the AGIP and SAFEN reports with published information from geological, volcanological, petrological, petrophysical and geophysical studies, this paper presents an improved picture of the Campi Flegrei caldera that will be useful for volcanic hazard assessment and mitigation in the Naples area and for future research planning. The results suggest that intra-caldera activity has been influenced by how the magmatic system at depths greater than about 4 km has determined the transfer of magma, volatiles, and heat to the overlying geothermal system and, ultimately, to the surface. In particular, intriguing is that the most volcanically active central-eastern sector of the caldera, which is subject to intense bradyseismic ground movement and gas emission, coincides with a structurally delimited subsurface rock volume characterized by an uprising of the 100 °C isotherm, a deep water supply to the shallower aquifer, the early disappearance of secondary calcite, LP seismicity and high seismic S-wave attenuation. In this area, we also document evidence of repeated injection at depths of c. 1.5-3.0 km of isolated and small-volume batches of magma, where occurred their crystallization and degassing. Shallow intrusions and degassing of magma are thus identified as two of the key processes that drive unrest in Campi Flegrei.

Piochi, M.; Kilburn, C. R. J.; Di Vito, M. A.; Mormone, A.; Tramelli, A.; Troise, C.; De Natale, G.

2014-03-01

174

Real-time fracture monitoring in Engineered Geothermal Systems with seismic waves  

SciTech Connect

As proposed, the main effort in this project is the development of software capable of performing real-time monitoring of micro-seismic activity recorded by an array of sensors deployed around an EGS. The main milestones are defined by the development of software to perform the following tasks: • Real-time micro-earthquake detection and location • Real-time detection of shear-wave splitting • Delayed-time inversion of shear-wave splitting These algorithms, which are discussed in detail in this report, make possible the automatic and real-time monitoring of subsurface fracture systems in geothermal fields from data collected by an array of seismic sensors. Shear wave splitting (SWS) is parameterized in terms of the polarization of the fast shear wave and the time delay between the fast and slow shear waves, which are automatically measured and stored. The measured parameters are then combined with previously measured SWS parameters at the same station and used to invert for the orientation (strike and dip) and intensity of cracks under that station. In addition, this grant allowed the collection of seismic data from several geothermal regions in the US (Coso) and Iceland (Hengill) to use in the development and testing of the software.

Jose A. Rial; Jonathan Lees

2009-03-31

175

Assessment of the Geothermal System Near Stanley, Idaho  

SciTech Connect

The City of Stanley, Idaho (population 63) is situated in the Salmon River valley of the central Idaho highlands. Due to its location and elevation (6270 feet amsl) it is one of the coldest locales in the continental U.S., on average experiencing frost 290 days of the year as well as 60 days of below zero (oF) temperatures. Because of high snowfall (76 inches on average) and the fact that it is at the terminus of its rural grid, the city also frequently endures extended power outages during the winter. To evaluate its options for reducing heating costs and possible local power generation, the city obtained a rural development grant from the USDA and commissioned a feasibility study through author Roy Mink to determine whether a comprehensive site characterization and/or test drilling program was warranted. Geoscience students and faculty at Idaho State University (ISU), together with scientists from the Idaho Geological Survey (IGS) and Idaho National Laboratory (INL) conducted three field data collection campaigns between June, 2011 and November, 2012 with the assistance of author Beckwith who arranged for food, lodging and local property access throughout the field campaigns. Some of the information collected by ISU and the IGS were compiled by author Mink and Boise State University in a series of progress reports (Makovsky et al., 2011a, b, c, d). This communication summarizes all of the data collected by ISU including data that were compiled as part of the IGS’s effort for the National Geothermal Data System’s (NGDS) data compilation project funded by the Department of Energy and coordinated by the Arizona Geological Survey.

Trent Armstrong; John Welhan; Mike McCurry

2012-06-01

176

Creation of an Enhanced Geothermal System through Hydraulic and Thermal Stimulation  

SciTech Connect

This report describes a 10-year DOE-funded project to design, characterize and create an Engineered Geothermal System (EGS) through a combination of hydraulic, thermal and chemical stimulation techniques. Volume 1 describes a four-year Phase 1 campaign, which focused on the east compartment of the Coso geothermal field. It includes a description of the geomechanical, geophysical, hydraulic, and geochemical studies that were conducted to characterize the reservoir in anticipation of the hydraulic stimulation experiment. Phase 1 ended prematurely when the drill bit intersected a very permeable fault zone during the redrilling of target stimulation well 34-9RD2. A hydraulic stimulation was inadvertently achieved, however, since the flow of drill mud from the well into the formation created an earthquake swarm near the wellbore that was recorded, located, analyzed and interpreted by project seismologists. Upon completion of Phase 1, the project shifted focus to a new target well, which was located within the southwest compartment of the Coso geothermal field. Volume 2 describes the Phase 2 studies on the geomechanical, geophysical, hydraulic, and geochemical aspects of the reservoir in and around target-stimulation well 46A-19RD, which is the deepest and hottest well ever drilled at Coso. Its total measured depth exceeding 12,000 ft. It spite of its great depth, this well is largely impermeable below a depth of about 9,000 ft, thus providing an excellent target for stimulation. In order to prepare 46A-19RD for stimulation, however, it was necessary to pull the slotted liner. This proved to be unachievable under the budget allocated by the Coso Operating Company partners, and this aspect of the project was abandoned, ending the program at Coso. The program then shifted to the EGS project at Desert Peak, which had a goal similar to the one at Coso of creating an EGS on the periphery of an existing geothermal reservoir. Volume 3 describes the activities that the Coso team contributed to the Desert Peak project, focusing largely on a geomechanical investigation of the Desert Peak reservoir, tracer testing between injectors 21-2 and 22-22 and the field�������¢����������������s main producers, and the chemical stimulation of target well 27-15.

Rose, Peter Eugene [Energy and Geoscience Institute at the University of Utah] [Energy and Geoscience Institute at the University of Utah

2013-04-15

177

Creation of an Enhanced Geothermal System through Hydraulic and Thermal Stimulation  

SciTech Connect

This report describes a 10-year DOE-funded project to design, characterize and create an Engineered Geothermal System (EGS) through a combination of hydraulic, thermal and chemical stimulation techniques. Volume 1 describes a four-year Phase 1 campaign, which focused on the east compartment of the Coso geothermal field. It includes a description of the geomechanical, geophysical, hydraulic, and geochemical studies that were conducted to characterize the reservoir in anticipation of the hydraulic stimulation experiment. Phase 1 ended prematurely when the drill bit intersected a very permeable fault zone during the redrilling of target stimulation well 34-9RD2. A hydraulic stimulation was inadvertently achieved, however, since the flow of drill mud from the well into the formation created an earthquake swarm near the wellbore that was recorded, located, analyzed and interpreted by project seismologists. Upon completion of Phase 1, the project shifted focus to a new target well, which was located within the southwest compartment of the Coso geothermal field. Volume 2 describes the Phase 2 studies on the geomechanical, geophysical, hydraulic, and geochemical aspects of the reservoir in and around target-stimulation well 46A-19RD, which is the deepest and hottest well ever drilled at Coso. Its total measured depth exceeding 12,000 ft. It spite of its great depth, this well is largely impermeable below a depth of about 9,000 ft, thus providing an excellent target for stimulation. In order to prepare 46A-19RD for stimulation, however, it was necessary to pull the slotted liner. This proved to be unachievable under the budget allocated by the Coso Operating Company partners, and this aspect of the project was abandoned, ending the program at Coso. The program then shifted to the EGS project at Desert Peak, which had a goal similar to the one at Coso of creating an EGS on the periphery of an existing geothermal reservoir. Volume 3 describes the activities that the Coso team contributed to the Desert Peak project, focusing largely on a geomechanical investigation of the Desert Peak reservoir, tracer testing between injectors 21-2 and 22-22 and the field�s main producers, and the chemical stimulation of target well 27-15.

Rose, Peter Eugene [Energy and Geoscience Institute at the Univerity of Utah] [Energy and Geoscience Institute at the Univerity of Utah

2013-04-15

178

Advances in geothermal energy use  

SciTech Connect

One of the earliest examples of large scale use of the geothermal energy is the district heating system in Boise, Idaho. Established in 1892, this system now serves 266 customers--mostly residential. Today, excluding heat pumps, there are about 300 sites in America where geothermal energy is currently used in various applications; including district heating, absorption cooling and refrigeration, industrial processes, aquaculture, horticulture, and snow melting/freeze protection. Among these, 18 geothermal district heating systems are operating with 677 GBtu (714 TJ) total annual heat output. Geothermal activity was first generated in Italy, in 1904, with a 10 kWe capacity. Now, commercial power plants are in service using vapor-dominated and liquid-dominated plants with a world-wide installed capacity of 6 GWe. This paper looks at a hybrid cycle/integrated district HVAC system.

Kilkis, I.B. [Heatway Radiant Floors and Snowmelting, Springfield, MO (United States). Research and Development Dept.; Eltez, M. [Ege Univ., Izmir (Turkey)

1996-10-01

179

Geochemical properties of groundwater used to geothermal cooling and heating system  

NASA Astrophysics Data System (ADS)

Recently, geothermal cooling and heating system has been used in many countries to reduce emission of greenhouse gases such as water vapour and carbon dioxide (CO2). Especially, CO2 is emitted from combustion of fossil fuel used for cooling and heating of buildings. Therefore, many countries make an effort to reduce amount of CO2 emitted from use of fossil fuel. The geothermal cooling and heating system is good to reduce amount of CO2. Especially, open loop geothermal system shows good thermal efficiency. However, groundwater contaminations will be considered because groundwater is directly used in open loop geothermal system. This study was performed to examine chemical and isotope compositions of groundwater used in open loop geothermal system and to evaluate influence of the system on groundwater using hydrochemical modeling program (preequc). Water temperature of well used in the system (GH) and well around the system (GB) ranged from 8.4 to 17.0 ° and from 15.1 to 18.0 °, respectively. The water temperature in GH was lower than that in GB because of heating mode of the system. Also, EC in GH and GB showed significant difference. The variation trend of EC was different at each site where the system was installed. These results mean that main factors controlling EC in GH was not the system. Generally, EC of groundwater was influenced by water-rock interaction. However, DO and Eh hardly showed significant difference. The operation period of the system observed in this study was short than 5 years. Therefore, influence of the open loop geothermal system on groundwater did not shown significantly. However, while Fe2+ and Mn2+ were not observed in GB, these components were measured in GH. The concentrations of Fe2+ and Mn2+ in GH ranged from 0.02 to 0.14 mg/L and from 0.03 to 0.18 mg/L, respectively. These results mean that redox conditions of GH were changed by the system little by little. In this study, influence of the open loop geothermal system on groundwater did not shown significantly. However, change of redox condition was slightly observed. To significantly observe influence of the open loop geothermal system, monitoring for well installed the system is necessary during long period. This work was supported by the Energy Efficiency and Resources of the Korea Institute of Energy Technology Evaluation and Planning (KETEP) grant funded by the Korea government Ministry of Knowledge Economy (No.20123040110010).

Kim, Namju; Park, Youngyun; Lee, Jin-Yong

2013-04-01

180

A geochemical model of the Platanares geothermal system, Honduras  

USGS Publications Warehouse

Results of exploration drilling combined with results of geologic, geophysical, and hydrogeochemical investigations have been used to construct a geochemical model of the Platanares geothermal system, Honduras. Three coreholes were drilled, two of which produced fluids from fractured Miocene andesite and altered Cretaceous to Eocene conglomerate at 450 to 680 m depth. Large volume artesian flows of 160-165??C, predominantly bicarbonate water are chemically similar to, but slightly less saline than widespread boiling hot-spring waters. The chemistry of the produced fluid is dominated by equilibrium reactions in sedimentary rocks at greater depths and higher temperatures than those measured in the wells. Chemical, isotope, and gas geothermometers indicate a deep fluid temperature of 200-245??C and reflect a relatively short residence time in the fractures feeding the wells. Chloride-enthalpy relations as well as isotopic and chemical compositions of well discharges, thermal springs, and local cold waters support a conceptual model of ascending high-temperature (minimum 225??C) parent fluid that has cooled conductively to form the 160-165??C shallow (to 680 m) fluid encountered by the wells. The hot-spring waters are formed by boiling and steam loss from more or less conductively cooled parent fluid. The more dilute boiling spring waters (Cl = ???32 mg/kg) have cooled from > 225??C to about 160??C by conduction and from 160??C to 98??C by boiling. The most concentrated boiling spring waters (Cl = 37 mg/kg) have cooled from > 225??C to about 200??C by conduction and from 200??C to 98??C by boiling. Intermediate concentrations reflect mixed cooling paths. ?? 1991.

Janik, C. J.; Truesdell, A. H.; Goff, F.; Shevenell, L.; Stallard, M. L.; Trujillo, Jr. , P. E.; Counce, D.

1991-01-01

181

Dispersion in tracer flow in fractured geothermal systems  

Microsoft Academic Search

Interpretation of tracer tests is commonly based on the analysis of flow through a porous medium. In geothermal reservoirs however the principal permeability arises from fractures, and a porous medium approach is not applicable. The dispersion of tracer material flowing in a fracture is shown to be dominated by molecular diffusion across the fracture-a mechanism known as Taylor dispersion. For

Roland N. Horne; Fernando Rodriguez

1983-01-01

182

Temperature evaluation of the Bugok geothermal system, South Korea  

Microsoft Academic Search

Using a variety of chemical geothermometers and statistical analysis, we estimate the temperature of a possible deeper geothermal reservoir at Bugok, Southern Korea. Shallow thermal aquifers (down to about 400m depth) are under exploitation in this area; the temperatures (up to 78°C) of the produced fluids are the highest found in South Korea. Based on hydrochemical data and occurrence, the

Seong-Sook Park; Seong-Taek Yun; Gi-Tak Chae; Ian Hutcheon; Yong-Kwon Koh; Chil-Sup So; Hyeon-Su Choi

2006-01-01

183

Thermal regime of the Great Basin and its implications for enhanced geothermal systems and off-grid power  

USGS Publications Warehouse

The Basin and Range Province of the Western United States covers most of Nevada and parts of adjoining states. It was formed by east-west tectonic extension that occurred mostly between 50 and 10 Ma, but which still is active in some areas. The northern Basin and Range, also known as the Great Basin, is higher in elevation, has higher regional heat flow and is more tectonically active than the southern Basin and Range which encompasses the Mojave and Sonoran Deserts. The Great Basin terrane contains the largest number of geothermal power plants in the United States, although most electrical production is at The Geysers and in the Salton Trough. Installed capacities of electrical power plants in the Great Basin vary from 1 to 260 MWe. Productivity is limited largely by permeability, relatively small productive reservoir volumes, available water, market conditions and the availability of transmission lines. Accessible, in-place heat is not a limiting condition for geothermal systems in the Great Basin. In many areas, economic temperatures (>120°C) can be found at economically drillable depths making it an appropriate region for implementation of the concept of "Enhanced Geothermal Systems" (EGS). An incremental approach to EGS would involve increasing the productivity and longevity of existing hydrothermal systems. Those geothermal projects that have an existing power plant and transmission facilities are the most attractive EGS candidates. Sites that were not developed owing to marginal size, lack of intrinsic permeability, and distance to existing electrical grid lines are also worthy of consideration for off-grid power production in geographically isolated markets such as ranches, farms, mines, and smelters.

Sass, John H.; Walters, Mark A.

1999-01-01

184

Plant adaptation to extreme environments: the example of Cistus salviifolius of an active geothermal alteration field.  

PubMed

Cistus salviifolius is able to colonise one of the most extreme active geothermal alteration fields in terms of both soil acidity and hot temperatures. The analyses of morpho-functional and physiological characters, investigated in leaves of plants growing around fumaroles (G leaves) and in leaves developed by the same plants after transfer into growth chamber under controlled conditions (C leaves) evidenced the main adaptive traits developed by this pioneer plant in a stressful environment. These traits involved leaf shape and thickness, mesophyll compactness, stomatal and trichome densities, chloroplast size. Changes of functional and physiological traits concerned dry matter content, peroxide and lipid peroxidation, leaf area, relative water and pigment contents. A higher reducing power and antioxidant enzymatic activity were typical of G leaves. Though the high levels of stress parameters, G leaves showed stress-induced specific morphogenic and physiological responses putatively involved in their surviving in active geothermal habitats. PMID:24581804

Bartoli, Giacomo; Bottega, Stefania; Forino, Laura M C; Ciccarelli, Daniela; Spanò, Carmelina

2014-02-01

185

Gaseous Emissions from Steamboat Springs, Brady's Hot Springs, and Desert Peak Geothermal Systems, Nevada  

Microsoft Academic Search

Gaseous emissions from the landscape can be used to ex- plore for geothermal systems, characterize their lateral extent, or map the trends of concealed geologic structures that may provide important reservoir permeability at depth. Gaseous geochemical signatures vary from system to system and uti- lization of a multi-gas analytical approach to exploration or characterization should enhance the survey's clarity. This

Paul J. Lechler; Mark Coolbaugh

2007-01-01

186

Design of a low cost space heating system using warm geothermal or industrial effluents  

Microsoft Academic Search

The design of an effective heating system employing moderate temperature (100 to 150 F) geothermal waters to heat greenhouses without any backup conventional system is discussed. The use of nonspecialized materials is emphasized with the result that maintenance is simple, fast, and requires no skilled labor. The heat exchanger system development starts with conventional methods and evolves, through heat transfer

A. J. Pate; J. C. Batty

1977-01-01

187

Evaluating Importance of Heat Transport Mechanisms Neglected in Design of Low Temperature Geothermal Systems  

Microsoft Academic Search

Design calculations for geothermal heating and cooling systems usually simplify or neglect many of the heat transport processes occurring in the subsurface. This is despite the fact that system efficiency, sustainability, and environmental impact all depend on heat transport in the subsurface. Design standards for the most popular systems, which use borehole heat exchangers, usually assume purely conductive heat transport

C. D. Langevin; M. C. Sukop

2009-01-01

188

Secondary mineral growth in fractures in the Miravalles geothermal system, Costa Rica  

SciTech Connect

A mineralogical, fluid-chemical, and theoretical study of hydrothermal alteration in veins from drillcore from the Miravalles geothermal field, Costa Rica has revealed a complex history of mineral-fluid reaction which may be used to characterize changes in temperature and fluid composition with time. Mineralogical and mineral-chemical data are consistent with hydrothermal alteration in the temperature range 200{sup 0}-270{sup 0}C, with deeper portions of the system having undergone temperatures in excess of 300{sup 0}C. Thermodynamic calculations suggest that the observed alteration assemblage is not equilibrium with current well fluids, unless estimates of reservoir pH are incorrect. Fe-Al zoning of prehnite and epidote in veins is consistent with rapid, isothermal fluctuations in fluid composition at current reservoir temperatures, and may be due to changes in volatile content of the fluid due to tectonic activity.

Rochelle, C.A. (Leeds Univ. (UK). Dept. of Earth Sciences); Milodowski, A.E.; Savage, D. (British Geological Survey, Keyworth (UK). Fluid Processes Research Group); Corella, M. (Instituto Costarricense de Electricidad, San Jose (Costa Rica))

1989-01-01

189

(Sulfide-oxide-silicate phase equilibria and associated fluid inclusion properties in the Salton Sea geothermal system, California)  

SciTech Connect

Our studies involved petrographic, fluid inclusion, geochemical and stable isotopic studies of drillcores and fluids from the Salton Sea geothermal system. Our initial studies revealed the presence of previously-unrecognized evaporitic anhydrite at depth throughout the geothermal system. The high salinity of the Salton Sea geothermal brines previously had been attributed to low-temperature dissolution of surficial evaporitic deposits by meteoric waters. Our microthermometric studies of halite--containing fluid inclusions in the meta-evaporites indicated that the high salinity of the geothermal brines is derived in part from the hydrothermal metamorphism of relatively deeply-buried salt and evaporites. In addition, our research concentrated on mineralized fractures in drillcores.

McKibben, M.A.

1988-06-01

190

Sonoma State Hospital, Eldridge, California, geothermal-heating system: conceptual design and economic feasibility report  

SciTech Connect

The Sonoma State Mental Hospital, located in Eldridge, California, is presently equipped with a central gas-fired steam system that meets the space heating, domestic hot water, and other heating needs of the hospital. This system is a major consumer of natural gas - estimated at 259,994,000 cubic feet per year under average conditions. At the 1981 unit gas rate of $0.4608 per therm, an average of $1,258,000 per year is required to operate the steam heating system. The hospital is located in an area with considerable geothermal resources as evidenced by a number of nearby hot springs resorts. A private developer is currently investigating the feasibility of utilizing geothermally heated steam to generate electricity for sale to the Pacific Gas and Electric Company. The developer has proposed to sell the byproduct condensed steam to the hospital, which would use the heat energy remaining in the condensate for its own heating needs and thereby reduce the fossil fuel energy demand of the existing steam heating system. The geothermal heating system developed is capable of displacing an estimated 70 percent of the existing natural gas consumption of the steam heating system. Construction of the geothermal fluid distribution and collection system and the retrofits required within the buildings are estimated to cost $1,777,000. Annual expenses (operation and maintenance, insurance, and geothermal fluid purchase) have been estimated to be $40,380 per year in 1981 dollars. The proposed geothermal heating system could then be completely paid for in 32 months by the savings in natural gas purchases that would result.

Not Available

1982-02-01

191

Direct utilization of geothermal heat in cascade application to aquaculture and greenhouse systems at Navarro College. Annual report, January 1984September 1984  

Microsoft Academic Search

Progress is reported on a project to use the 130°F geothermal resource in central Texas. The system for cascading geothermal energy through aquaculture and greenhouse systems was completed and the first shrimp harvest was held. (MHR)

1984-01-01

192

Direct utilization of geothermal heat in cascade application to aquaculture and greenhouse systems at Navarro College. Annual report, January 1984-September 1984  

SciTech Connect

Progress is reported on a project to use the 130/sup 0/F geothermal resource in central Texas. The system for cascading geothermal energy through aquaculture and greenhouse systems was completed and the first shrimp harvest was held. (MHR)

Smith, K.

1984-09-01

193

Hydrology of the Greater Tongonan geothermal system, Philippines, as deduced from geochemical and isotopic data  

SciTech Connect

Fluids in the Greater Tongonan geothermal system exhibit a large positive {sup 18}O shift from the Leyte meteoric water line. However, there is also a significant shift in {sup 2}H. The {delta}{sup 2}H-{delta}{sup 18}O plot shows that the geothermal fluids may be derived by the mixing of meteoric water with local magmatic water. The most enriched water in the Greater Tongonan system, in terms of {delta}{sup 18}O, {delta}{sup 2}H and Cl, is comprised of approximately 40% magmatic water. Baseline isotope results support a hydrogeochemical model in which there is increasing meteoric water dilution to the southeast, from Mahiao to Sambaloran and towards Malitbog. The Cl-{delta}{sup 18}O plot confirms that the geothermal fluid in Mahanagdong, further southeast, is distinct from that of the Mahiao-Sambaloran-Malitbog system.

Alvis-Isidro, R.R.; Solana, R.R. [Philippine National Oil Co.-Energy Development Corp., Fort Bonifacio (Philippines)] [Philippine National Oil Co.-Energy Development Corp., Fort Bonifacio (Philippines); D`amore, F.; Nuti, S. [Inst. Internazionale per le Ricerche Geotermiche, Pisa (Italy)] [Inst. Internazionale per le Ricerche Geotermiche, Pisa (Italy); Gonfiantini, R. [International Atomic Energy Agency, Vienna (Austria)] [International Atomic Energy Agency, Vienna (Austria)

1993-10-01

194

Heat and mass transfer in the Klamath Falls, Oregon, geothermal system  

SciTech Connect

Over the last 50 years significant amounts of data have been obtained from the Klamath Falls geothermal resource. To date, the complexity of the system has perplexed researchers, leading to the development of only very generalized hydrogeologic and geothermal models of the area. Based on reevaluation of all available data, a detailed conceptual model for the Klamath Falls geothermal resource is proposed. A comprehensive 3-dimensional numerical model, based on the proposed conceptual model is also presented. This numerical model incorporates all of the main reservoir characteristics. Hot water recharge flows from depth, along a large normal fault, and flows into near surface permeable strata where it loses heat to surrounding beds and to mixing with cold regional groundwaters introduced from the north. By matching calculated and measured temperatures and pressures, hot and cold water recharge rates and the permeability distribution for the geothermal system are estimated. A semi-analytic solution and simple lumped parameter methods are also compared to the numerical analysis. Results suggest that the flow patterns within the geothermal system at Klamath Falls are complex and intimately associated with the permeability distribution and the pressures and temperatures at depth, within the faults.

Prucha, R.H.

1987-05-01

195

Seismic methods for resource exploration in enhanced geothermal systems  

SciTech Connect

A finite-difference modeling study of seismic wave propagation was conducted to determine how to best investigate subsurface faults and fracture zones in geothermal areas. The numerical model was created based on results from a previous seismic reflection experiment. A suite of fault models was investigated including blind faults and faults with surface expressions. The seismic data suggest that blind faults can be detected by a sudden attenuation of seismic wave amplitudes, as long the fault is located below the receiver array. Additionally, a conversion from P- to S-waves indicates the reflection and refraction of the P-waves while propagating across the fault. The drop in amplitudes and the excitation of S-waves can be used to estimate the location of the fault at depth. The accuracy of the numerical modeling depends on the availability of a priori in situ information (velocity and density) from borehole experiments in the geothermal area.

Gritto, Roland; Majer, Ernest L.

2002-06-12

196

Wine Valley Inn: A mineral water spa in Calistoga, California. Geothermal-energy-system conceptual design and economic feasibility  

SciTech Connect

The purpose of this study is to determine the engineering and economic feasibility for utilizing geothermal energy for air conditioning and service water heating at the Wine Valley Inn, a mineral water spa in Calistoga, California. The study evaluates heating, ventilating, air conditioning and water heating systems suitable for direct heat geothermal application. Due to the excellent geothermal temperatures available at this site, the mechanics and economics of a geothermally powered chilled water cooling system are evaluated. The Wine Valley Inn has the resource potential to have one of the few totally geothermal powered air conditioning and water heating systems in the world. This total concept is completely developed. A water plan was prepared to determine the quantity of water required for fresh water well development based on the special requirements of the project. An economic evaluation of the system is included to justify the added capital investment needed to build the geothermally powered mineral spa. Energy payback calculations are presented. A thermal cascade system is proposed to direct the geothermal water through the energy system to first power the chiller, then the space heating system, domestic hot water, the two spas and finally to heat the swimming pool. The Energy Management strategy required to automatically control this cascade process using industrial quality micro-processor equipment is described. Energy Management controls are selected to keep equipment sizing at a minimum, pump only the amount of geothermal water needed and be self balancing.

Not Available

1981-10-26

197

Structural Controls of a Blind Geothermal System in the Northern Pyramid Lake Area, Northwestern Nevada  

Microsoft Academic Search

Most geothermal systems in the Great Basin are fault con- trolled. Ongoing studies suggest that many of these systems occupy discrete steps in fault zones or lie in belts of intersect- ing, overlapping, and\\/or terminating faults. Fault interactions within these settings generate subvertical conduits of highly fractured rock and increase dilation, thereby allowing geother- mal fluids to approach the surface.

Garrett S. Vice; James E. Faulds; William J. Ehni; Mark F. Coolbaugh

2007-01-01

198

Understanding the Chena Hot Springs, Alaska, geothermal system using temperature and pressure data from exploration boreholes  

Microsoft Academic Search

Chena Hot Springs is a small, moderate temperature, deep circulating geothermal system, apparently typical of those associated to hot springs of interior Alaska. Multi-stage drilling was used in some exploration boreholes and was found to be useful for understanding subsurface flow characteristics and developing a conceptual model of the system. The results illustrate how temperature profiles illuminate varying pressure versus

Kamil Erkan; Gwen Holdmann; Walter Benoit; David Blackwell

2008-01-01

199

National Geothermal Data System: an Exemplar of Open Access to Data  

NASA Astrophysics Data System (ADS)

The National Geothermal Data System's (NGDS - www.geothermaldata.org) formal launch in 2014 will provide open access to millions of datasets, sharing technical geothermal-relevant data across the geosciences to propel geothermal development and production. With information from all of the Department of Energy's sponsored development and research projects and geologic data from all 50 states, this free, interactive tool is opening new exploration opportunities and shortening project development by making data easily discoverable and accessible. We continue to populate our prototype functional data system with multiple data nodes and nationwide data online and available to the public. Data from state geological surveys and partners includes more than 5 million records online, including 1.48 million well headers (oil and gas, water, geothermal), 732,000 well logs, and 314,000 borehole temperatures and is growing rapidly. There are over 250 Web services and another 138 WMS (Web Map Services) registered in the system as of August, 2013. Companion projects run by Boise State University, Southern Methodist University, and USGS are adding millions of additional data records. The National Renewable Energy Laboratory is managing the Geothermal Data Repository which will serve as a system node and clearinghouse for data from hundreds of DOE-funded geothermal projects. NGDS is built on the US Geoscience Information Network data integration framework, which is a joint undertaking of the USGS and the Association of American State Geologists (AASG). NGDS is fully compliant with the White House Executive Order of May 2013, requiring all federal agencies to make their data holdings publicly accessible online in open source, interoperable formats with common core and extensible metadata. The National Geothermal Data System is being designed, built, deployed, and populated primarily with grants from the US Department of Energy, Geothermal Technologies Office. To keep this operational system sustainable after the original implementation will require four core elements: continued serving of data and applications by providers; maintenance of system operations; a governance structure; and an effective business model. Each of these presents a number of challenges currently under consideration.

Allison, M. L.; Richard, S. M.; Blackman, H.; Anderson, A.

2013-12-01

200

A Simple Model for Probabilistic Seismic Hazard Analysis of Induced Seismicity Associated With Deep Geothermal Systems  

NASA Astrophysics Data System (ADS)

In the research project MAGS (Microseismic activity of geothermal systems) funded by the German Federal Ministry of Environment (BMU) a simple model was developed to determine seismic hazard as the probability of the exceedance of ground motion of a certain size. Such estimates of the annual frequency of exceedance of prescriptive limits of e.g. seismic intensities or ground motions are needed for the planning and licensing, but likewise for the development and operation of deep geothermal systems. For the development of the proposed model well established probabilistic seismic hazard analysis (PSHA) methods for the estimation of the hazard for the case of natural seismicity were adapted to the case of induced seismicity. Important differences between induced and natural seismicity had to be considered. These include significantly smaller magnitudes, depths and source to site distances of the seismic events and, hence, different ground motion prediction equations (GMPE) that had to be incorporated to account for the seismic amplitude attenuation with distance as well as differences in the stationarity of the underlying tectonic and induced processes. Appropriate GMPE's in terms of PGV (peak ground velocity) were tested and selected from the literature. The proposed model and its application to the case of induced seismicity observed during the circulation period (operation phase of the plant) at geothermal sites in Germany will be presented. Using GMPE's for PGV has the advantage to estimate hazard in terms of velocities of ground motion, which can be linked to engineering regulations (e.g. German DIN 4150) which give prescriptive standards for the effects of vibrations on buildings and people. It is thus possible to specify the probability of exceedance of such prescriptive standard values and to decide whether they can be accepted or not. On the other hand hazard curves for induced and natural seismicity can be compared to study the impact at a site. Preliminary results for a site in Germany (for stiff soil, ignoring site effects) indicate higher frequencies of exceedance for induced seismicity than for natural seismicity only for low PGV values.

Schlittenhardt, Joerg; Spies, Thomas; Kopera, Juergen; Morales Aviles, Wilhelm

2014-05-01

201

Numerical modeling of geothermal heat pump system: evaluation of site specific groundwater thermal impact  

NASA Astrophysics Data System (ADS)

A pilot plant using a geothermal open-loop heat pump system has been realized in the city of Vicenza (Northern Italy), in order to meet the heating and cooling needs of the main monumental building in the historical center, the Palladian Basilica. The low enthalpy geothermal system consists of a pumping well and a reinjection well, both intercepting the same confined aquifer; three other monitoring wells have been drilled and then provided with water level and temperature dataloggers. After about 1 year and a half of activity, during a starting experimental period of three years, we have now the opportunity to analyze long term groundwater temperature data series and to evaluate the numerical modeling reliability about thermal impact prediction. The initial model, based on MODFLOW and SHEMAT finite difference codes, has been calibrated using pumping tests and other field investigations data, obtaining a valid and reliable groundwater flow simulation. But thermal parameters, such as thermal conductivity and volumetric heat capacity, didn't have a site specific direct estimation and therefore they have been assigned to model cells referring to bibliographic standards, usually derived from laboratory tests and barely representing real aquifer properties. Anyway preliminary heat transport results have been compared with observed temperature trends, showing an efficient representation of the thermal plume extension and shape. The ante operam simulation could not consider heat pump real utilization, that happened to be relevantly different from the expected project values; so the first numerical model could not properly simulate the groundwater temperature evolution. Consequently a second model has been implemented, in order to calibrate the mathematical simulation with monitored groundwater temperature datasets, trying to achieve higher levels of reliability in heat transport phenomena interpretation. This second step analysis focuses on aquifer thermal parameters calibration and includes a new finite element FEFLOW simulation, as an useful comparison between different approaches to heat transport modeling.

Pedron, Roberto; Sottani, Andrea; Vettorello, Luca

2014-05-01

202

Hydrochemistry and geothermometrical modeling of low-temperature Panticosa geothermal system (Spain)  

NASA Astrophysics Data System (ADS)

The chemical characteristics of the low-temperature geothermal system of Panticosa (Spain) were investigated in order to determine the water temperature at the reservoir and to identify the main geochemical processes that affect the water composition during the ascent of the thermal waters. In general, the studied waters are similar to other geothermal systems in the Pyrenees, belonging to the group of granite-related alkaline thermal waters (high pH, low total dissolved solids, very low magnesium concentration, and sodium as the dominant cation). According to the alkaline pH of these waters, they have a very low CO2 partial pressure, bicarbonate is the dominant anion and silica is partially ionized as H3SiO4-. The unusually active acid-base pairs (HCO3-/CO32 - and, mainly, H4SiO4/H3SiO4-) act as homogeneous pH buffers and contribute to the total alkalinity in these alkaline waters. On the basis of the study of the conservative elements, a mixing process between a hot and a cold end-member has been identified. Additionally, in order to determinate the water temperature at the reservoir, several geothermometric techniques have been applied, including both geothermometrical modeling and classical geothermometrical calculations. The geothermometrical modeling seems to indicate that thermal waters re-equilibrate with respect to calcite and kaolinite during their ascent to the surface. Modeling results suggest that these thermal waters would be in equilibrium with respect to albite, K-feldspar, quartz, calcite, kaolinite and zoisite at a similar temperature of 90 ± 20 °C in the reservoir, which is in good agreement with the results obtained by applying the classical geothermometers.

Asta, Maria P.; Gimeno, Maria J.; Auqué, Luis F.; Gómez, Javier; Acero, Patricia; Lapuente, Pilar

2012-08-01

203

Feasibility study of geothermal energy for heating greenhouses. Final report  

Microsoft Academic Search

The technical feasibility of heating greenhouses with geothermal heat is established. Off-the-shelf equipment suitable for geothermal heating is readily available. A procedure is given to economically examine a geothermal site for its suitability. Generally, geothermal heating systems are capital intensive. Where the geothermal energy is free the geothermal system is very attractive and where the cost of geothermal heat is

LaFrance

1979-01-01

204

Selected data for low-temperature (less than 90{sup 0}C) geothermal systems in the United States: reference data for US Geological Survey Circular 892  

SciTech Connect

Supporting data are presented for the 1982 low-temperature geothermal resource assessment of the United States. Data are presented for 2072 geothermal sites which are representative of 1168 low-temperature geothermal systems identified in 26 States. The low-temperature geothermal systems consist of 978 isolated hydrothermal-convection systems, 148 delineated-area hydrothermal-convection systems, and 42 delineated-area conduction-dominated systems. The basic data and estimates of reservoir conditions are presented for each geothermal system, and energy estimates are given for the accessible resource base, resource, and beneficial heat for each isolated system.

Reed, M.J.; Mariner, R.H.; Brook, C.A.; Sorey, M.L.

1983-12-15

205

Emerging geothermal energy technologies  

Microsoft Academic Search

Geothermal energy, whether as a source of electricity or to heat or cool buildings, has an enormous potential as a renewable energy source. This paper presents a broad overview of geothermal energy, with a focus on the emerging technologies of Enhanced Geothermal Systems (EGS) and Ground Source Heat Pumps (GSHPs). EGS and GSHP systems are important because of their potential

I. W. Johnston; S. Colls

2011-01-01

206

Temperatures, heat flow, and water chemistry from drill holes in the Raft River geothermal system, Cassia County, Idaho  

SciTech Connect

The Raft River area of Idaho contains a geothermal system of intermediate temperatures (approx. = 150/sup 0/C) at depths of about 1.5 km. Outside of the geothermal area, temperature measurements in three intermediate-depth drill holes (200 to 400 m) and one deep well (1500 m) indicate that the regional conductive heat flow is about 2.5 ..mu..cal/cm/sup 2/ sec or slightly higher and that temperature gradients range from 50/sup 0/ to 60/sup 0/C/km in the sediments, tuffs, and volcanic debris that fill the valley. Within and close to the geothermal system, temperature gradients in intermediate-depth drill holes (100 to 350 m) range from 120/sup 0/ to more than 600/sup 0/C/km, the latter value found close to an artesian hot well that was once a hot spring. Temperatures measured in three deep wells (1 to 2 km) within the geothermal area indicate that two wells are in or near an active upflow zone, whereas one well shows a temperature reversal. Assuming that the upflow is fault controlled, the flow is estimated to be 6 liter/sec per kilometer of fault length. From shut-in pressure data and the estimated flow, the permeability times thickness of the fault is calculated to be 2.4 darcy m. Chemical analyses of water samples from old flowing wells, recently completed intermediate-depth drill holes, and deep wells show a confused pattern. Geothermometer temperatures of shallow samples suggest significant re-equilibration at temperatures below those found in the deep wells. Silica geothermometer temperatures of water samples from the deep wells are in reasonable agreement with measured temperatures, whereas Na-K-Ca temperatures are significantly higher than measured temperatures. The chemical characteristics of the water, as indicated by chloride concentration, are extremely variable in shallow and deep samples. Chloride concentrations of the deep samples range from 580 to 2200 mg/kg.

Nathenson, M.; Urban, T.C.; Diment, W.H.; Nehring, N.L.

1980-01-01

207

Deep geothermal resources and energy: Current research and developments  

NASA Astrophysics Data System (ADS)

Energy from deep geothermal resources plays an increasing role in many European countries in their efforts to increase the proportion of renewables in their energy portfolio. Deep geothermal heat and electric power have a high load factor, are sustainable and environmentally friendly. However, the safe, sustainable, and economic development of deep geothermal resources, also in less favourable regions, faces a number of issues requiring substantial research efforts: (1) The probability of finding an unknown geothermal reservoir has to be improved. (2) Drilling methods have to be better adapted and developed to the specific needs of geothermal development. (3) The assessment of the geothermal potential should provide more reliable and clear guidelines for the development. (4) Stimulation methods for enhanced geothermal systems (EGS) have to be refined to increase the success rate and reduce the risk associated with induced seismicity. (5) Operation and maintenance in aggressive geothermal environments require specific solutions for corrosion and scaling problems. (6) Last but not least, emerging activities to harness energy from supercritical reservoirs would make significant progress with qualified input from research. In particular, sedimentary basins like e.g. the North German and Polish Basin, the Pannonian Basin, the Po Valley, the Bavarian Molasse Basin or the Upper Rhine Graben have a high geothermal potential, even if geothermal gradients are moderate. We will highlight projects that aim at optimizing exploration, characterization, and modeling prior to drilling and at a better understanding of physical, hydraulic and chemical processes during operation of a geothermal power plant. This includes geophysical, geological and geochemical investigations regarding potential geothermal reservoirs in sedimentary basins, as well as modelling of geothermally relevant reservoir parameters that influence the potential performance and long-term behavior of a future geothermal power plant. In our overview we will also highlight contributions of EGU2012-sessions ERE1.6 (Geothermal energy from deep sedimentary basins - exploration, exploitation, characterization and modeling) and ERE1.7 (Development of deep geothermal resources).

Manzella, A.; Milsch, H.; Hahne, B.; van Wees, J. D.; Bruhn, D.

2012-04-01

208

Comparison of Selective Culturing and Biochemical Techniques for Measuring Biological Activity in Geothermal Process Fluids  

SciTech Connect

For the past three years, scientists at the Idaho National Engineering and Environmental Laboratory have been conducting studies aimed at determining the presence and influence of bacteria found in geothermal plant cooling water systems. In particular, the efforts have been directed at understanding the conditions that lead to the growth and accumulation of biomass within these systems, reducing the operational and thermal efficiency. Initially, the methods selected were based upon the current practices used by the industry and included the collection of water quality parameters, the measurement of soluble carbon, and the use of selective medial for the determination of the number density of various types of organisms. This data has been collected on a seasonal basis at six different facilities located at the Geysers’ in Northern California. While this data is valuable in establishing biological growth trends in the facilities and providing an initial determination of upset or off-normal conditions, more detailed information about the biological activity is needed to determine what is triggering or sustaining the growth in these facilities in order to develop improved monitoring and treatment techniques. In recent years, new biochemical approaches, based upon the analyses of phospholipid fatty acids and DNA recovered from environmental samples, have been developed and commercialized. These techniques, in addition to allowing the determination of the quantity of biomass, also provide information on the community composition and the nutritional status of the organisms. During the past year, samples collected from the condenser effluents of four of the plants from The Geysers’ were analyzed using these methods and compared with the results obtained from selective culturing techniques. The purpose of this effort was to evaluate the cost-benefit of implementing these techniques for tracking microbial activity in the plant study, in place of the selective culturing analyses that are currently the industry standard.

Pryfogle, Peter Albert

2000-09-01

209

3-D Magnetotelluric Exploration of Tenerife Geothermal System (Canary Islands, Spain)  

NASA Astrophysics Data System (ADS)

The resistivity structure of the Tenerife geothermal system has been determined by the 3-D inversion of data from different magnetotelluric surveys. In this paper, the ocean and topography effects on the magnetotelluric data were investigated by constructing a 3-D conceptual geoelectrical model of the island. The study showed that these effects should be taken into account in order to obtain a reliable subsurface model of the island. Data from 148 sites were used during three-dimensional inversion. The most interesting feature in the final geoelectrical model of the geothermal system is a low resistivity structure (<10 ?m) above the resistive core of the system. The low resistivity structure has been interpreted as a hydrothermal clay alteration cap typically generated in the conventional geothermal systems. The resistivity model has been correlated with a recent seismic velocity model, showing that a low resistivity structure surrounds an area with high P wave velocity and medium-high resistivity. This medium-high resistivity area can be associated with a slowly solidified magma and, therefore, with a hotter part of the geothermal system.

Piña-Varas, P.; Ledo, J.; Queralt, P.; Marcuello, A.; Bellmunt, F.; Hidalgo, R.; Messeiller, M.

2014-02-01

210

Rock specific hydraulic fracturing and matrix acidizing to enhance a geothermal system — Concepts and field results  

NASA Astrophysics Data System (ADS)

Enhanced geothermal systems (EGS) are engineered reservoirs developed to extract economic amounts of heat from low permeability and/or porosity geothermal resources. To enhance the productivity of reservoirs, a site specific concept is necessary to actively make reservoir conditions profitable using specially adjusted stimulation treatments, such as multi fracture concepts and site specific well path design. The results of previously performed stimulation treatments in the geothermal research well GtGrSk4/05 at Groß Schönebeck, Germany are presented. The reservoir is located at a 4100-4300 m depth within the Lower Permian of the NE German Basin with a bottom-hole temperature of 150 °C. The reservoir rock is classified by two lithological units from bottom to top: volcanic rocks (andesitic rocks) and siliciclastics ranging from conglomerates to fine-grained sandstones (fluvial sediments). The stimulation treatments included multiple hydraulic stimulations and an acid treatment. In order to initiate a cross-flow from the sandstone layer, the hydraulic stimulations were performed in different depth sections (two in the sandstone section and one in the underlying volcanic section). In low permeability volcanic rocks, a cyclic hydraulic fracturing treatment was performed over 6 days in conjunction with adding quartz in low concentrations to maintain a sustainable fracture performance. Flow rates of up to 150 l/s were realized, and a total of 13,170 m 3 of water was injected. A hydraulic connection to the sandstone layer was successfully achieved in this way. However, monitoring of the water level in the offsetting well EGrSk3/90, which is 475 m apart at the final depth, showed a very rapid water level increase due to the stimulation treatment. This can be explained by a connected fault zone within the volcanic rocks. Two gel-proppant treatments were performed in the slightly higher permeability sandstones to obtain long-term access to the reservoir rocks. During each treatment, a total of 100 ton of high strength proppants was injected with 500 m 3 of cross-linked gel. The subsequent production test in conjunction with flowmeter logging showed an improvement of productivity by a factor of more than 4. Due to assumed residual drilling mud (constituents: calcite, dolomite, and aragonite) in the near-wellbore vicinity, an acid matrix stimulation was performed thereafter using a coil tubing unit. The following nitrogen lift test demonstrated another increase of productivity by 30-50% to an overall increase by a factor of 5.5-6.2.

Zimmermann, Günter; Blöcher, Guido; Reinicke, Andreas; Brandt, Wulf

2011-04-01

211

Magmatic Chimney Beneath Telaga Bodas Revealed by Magnetotellurics Profiling: A Case Study at the Karaha Bodas Geothermal System, Indonesia  

Microsoft Academic Search

Karaha-Telaga Bodas is a partially vapor-dominated geothermal system located on the flanks of Galunggung Volcano in Java, Indonesia. Fumaroles, hot springs and a shallow acid lake occur at the southern (Telaga Bodas) end of the geothermal area. Enrichments in chloride, fluoride, and sulfur in the lake water and the presence of tourmaline, fluorite, and native sulfur at depth are related

I. Raharjo; P. Wannamaker; J. N. Moore; R. Allis; D. Chapman

2002-01-01

212

Design and development of a greenhouse growing system with a cooling facility using geothermal energy; Part 1  

Microsoft Academic Search

The purpose of the present work was to develop a greenhouse growing system with a night cooling facility using geothermal energy to grow fall and winter vegetables during high summer temperatures. In this paper, the authors first designed and constructed a greenhouse cooling facility using geothermal water for the driving energy, and then conducted a cooling performance test and growth

Shunichiro Tanaka; Sadato Ishibashi; Masami Kaieda

1994-01-01

213

Use of solar assisted geothermal heat pump and small wind turbine systems for heating agricultural and residential buildings  

Microsoft Academic Search

The main objective of the present study is twofold: (i) to analyze thermal loads of the geothermally and passively heated solar greenhouses; and (ii) to investigate wind energy utilization in greenhouse heating which is modeled as a hybrid solar assisted geothermal heat pump and a small wind turbine system which is separately installed in the Solar Energy Institute of Ege

Onder Ozgener

2010-01-01

214

Geothermal energy in Nevada  

SciTech Connect

The nature of goethermal resources in Nevada and resource applications are discussed. The social and economic advantages of utilizing geothermal energy are outlined. Federal and State programs established to foster the development of geothermal energy are discussed. The names, addresses, and phone numbers of various organizations actively involved in research, regulation, and the development of geothermal energy are included. (MHR)

Not Available

1980-01-01

215

National Geothermal Data System (USA): an Exemplar of Open Access to Data  

NASA Astrophysics Data System (ADS)

The National Geothermal Data System's (NGDS - www.geothermaldata.org) formal launch in April, 2014 will provide open access to millions of data records, sharing -relevant geoscience and longer term to land use data to propel geothermal development and production. NGDS serves information from all of the U.S. Department of Energy's sponsored development and research projects and geologic data from all 50 states, using free and open source software. This interactive online system is opening new exploration opportunities and potentially shortening project development by making data easily discoverable, accessible, and interoperable. We continue to populate our prototype functional data system with multiple data nodes and nationwide data online and available to the public. Data from state geological surveys and partners includes more than 6 million records online, including 1.72 million well headers (oil and gas, water, geothermal), 670,000 well logs, and 497,000 borehole temperatures and is growing rapidly. There are over 312 interoperable Web services and another 106 WMS (Web Map Services) registered in the system as of January, 2014. Companion projects run by Southern Methodist University and U.S. Geological Survey (USGS) are adding millions of additional data records. The DOE Geothermal Data Repository, currently hosted on OpenEI, is a system node and clearinghouse for data from hundreds of U.S. DOE-funded geothermal projects. NGDS is built on the US Geoscience Information Network (USGIN) data integration framework, which is a joint undertaking of the USGS and the Association of American State Geologists (AASG). NGDS complies with the White House Executive Order of May 2013, requiring all federal agencies to make their data holdings publicly accessible online in open source, interoperable formats with common core and extensible metadata. The National Geothermal Data System is being designed, built, deployed, and populated primarily with support from the US Department of Energy, Geothermal Technologies Office. To keep this system operational after the original implementation will require four core elements: continued serving of data and applications by providers; maintenance of system operations; a governance structure; and an effective business model. Each of these presents a number of challenges currently under consideration.

Allison, M. Lee; Richard, Stephen; Blackman, Harold; Anderson, Arlene; Patten, Kim

2014-05-01

216

36Cl/Cl ratios in geothermal systems: preliminary measurements from the Coso Field  

SciTech Connect

The {sub 36}Cl/Cl isotopic composition of chlorine in geothermal systems can be a useful diagnostic tool in characterizing hydrologic structure, in determining the origins and age of waters within the systems, and in differentiating the sources of chlorine (and other solutes) in the thermal waters. The {sub 36}Cl/Cl values for several geothermal water samples and reservoir host rock samples from the Coso, California geothermal field have been measured for these purposes. The results indicate that most of the chlorine is not derived from the dominant granitoid that host the geothermal system. If the chlorine was originally input into the Coso subsurface through meteoric recharge, that input occurred at least 1-1.25 million years ago. The results suggest that the thermal waters could be connate waters derived from sedimentary formations, presumably underlying and adjacent top the granitic rocks, which have recently migrated into the host rocks. Alternatively, most of the chlorine but not the water, may have recently input into the system from magmatic sources. In either case, the results indicate that most of the chlorine in the thermal waters has existed within the granitoid host rocks for no more than about 100,00-200,00 years. this residence time for the chlorine is similar to residence times suggested by other researchers for chlorine in deep groundwaters of the Mono Basin north of the Coso field.

Nimz, G.J.; Moore, J.N.; Kasameyer, P.W.

1997-07-01

217

Process and system for recovery of energy from geothermal brines and other hot water sources  

Microsoft Academic Search

Process and system for recovery of energy from geothermal brines and other hot water sources comprises direct contact heat exchange between the brine or hot water, and a hydrocarbon working fluid, E.G. N-butane, in a heat transfer column, the heat transfer column being operated at or above the critical pressure of the working fluid, and the hot brine or hot

Woinsky

1982-01-01

218

Process and system for recovery of energy from geothermal brines and other hot water containing sources  

Microsoft Academic Search

Process and system for recovery of energy from geothermal brines and other hot water sources by direct contact heat exchange between the brine or hot water, and a working fluid exiting the top of the heat transfer column is expanded through an expander to produce work. The discharge from the expander is cooled to condense working fluid which is separated

Woinsky

1981-01-01

219

Process and system for recovery of energy from geothermal brines and other hot water sources  

Microsoft Academic Search

Process and system for recovery of energy from geothermal brines and other hot water sources are disclosed, which comprise direct contact heat exchange between the brine or hot water, and a hydrocarbon working fluid, E.G. N-butane, in a heat transfer column, the heat transfer column being operated at or above the critical pressure of the working fluid, and the hot

Woinsky

1982-01-01

220

Variation in sericite compositions from fracture zones within the Coso Hot Springs geothermal system  

Microsoft Academic Search

Two types of white micas are found in drillhole samples within the geothermal system at Coso Hot Springs. Low-permeability zones of the crystalline basement contain coarse-grained relict muscovite, whereas rock alteration near fracture zones at temperatures > 150°C is characterized by abundant finegrained sericite in association with secondary calcite and quartz and unaltered relict microcline. In this hydrothermal sericite there

Barbara P. Bishop; Dennis K. Bird

1987-01-01

221

Energy and exergy analysis of a ground source (geothermal) heat pump system  

Microsoft Academic Search

Ground source heat pumps (GSHPs), often referred to as geothermal heat pumps (GHPs), offer an attractive option for heating and cooling residential and commercial buildings owing to their higher energy efficiency compared with conventional systems. GSHPs have been used for four years in the Turkish market, although they have been in use for more years in developed countries. The purpose

A. Hepbasli; O. Akdemir

2004-01-01

222

Gravitational stability of water over steam in vapor-dominated geothermal systems  

Microsoft Academic Search

Vapor-dominated geothermal systems exist in a most extraordinary state: a condensate or water layer several hundred meters thick overlies a main steam zone of undetermined thickness. Why doesn't the water fall down? We show that a heavy fluid phase overlying a light phase of the same fluid in a porous medium can be stable provided the permeability in the vicinity

Gerald Schubert; Joe M. Straus

1980-01-01

223

Precision gravity network for monitoring the Lassen geothermal system, Northern California  

USGS Publications Warehouse

A precision gravity network consisting of approximately 50 stations was established to monitor the Lassen geothermal system. The network was surveyed during the summer of 1982 and tied to a similar network established in 1981. Measurements yielded relative gravity values at the network stations with average uncertainties of 0.007 mGal (1 computed standard error).

Jachens, Robert C.; Saltus, R. W.

1983-01-01

224

Thermal Modelling of Amagmatic Heat Sources as an Exploration Tool for Hot Rock Geothermal Systems  

NASA Astrophysics Data System (ADS)

Geothermal resources in Australia are amagmatic, "Hot Rock" systems, and unrelated to active volcanism or plate margin collision. Instead, these resources are typically associated with heat from radioactive decay in high-heat-producing (HHP) granites (granites containing high concentrations of U, Th and K), coupled with thermal insulation from a thick sediment cover. A greater understanding of the ideal geological components of the Hot Rock system is needed to assist geothermal exploration and reduce risk. Existing geothermal data for Australia (borehole temperatures and heat flow determinations) are limited and collection of additional data is both time consuming and restricted to accessing wells drilled for other purposes. To aid in targeting and prioritizing areas for further study (i.e., evaluations of permeabilities and flow rates), GA has undertaken synthetic thermal modelling, constrained by available geological and geophysical datasets. 150,000 discrete numerical simulations were performed using the SHEMAT computer code. The models were designed to explore the range of geological conditions present in Australia and include variations in intrusive geometry and heat production, sediment thickness and thermal conductivity, basement heat production and basal heat flow. In order to facilitate computation and analysis, plutons were modelled as radially symmetrical cylinders and advective heat transfer was considered to be negligible. The results of the synthetic modelling indicate that significant heat can be generated by granites and trapped in geologically realistic conditions. Temperatures >160°C can be produced with heat production values as low as 2.0 ?W/m3, but these scenarios require either unusually large pluton diameters (>50 km), low sediment thermal conductivity (<1.75 W/mK), or high basal heat flow values (>0.05 W/m2). The most geologically reasonable conditions that result in temperatures >160°C, are: pluton diameters 30-40 km; heat production of 4.0-5.0 ?W/m3; a basal heat flow of 0.04 W/m2; and basin thicknesses of >3 km. Threshold values for the various parameters can be derived for higher, more economically desirable temperatures (e.g., 220°C), but will require increasingly anomalous conditions. These findings provide a framework for identifying geologically-suitable areas where favourable temperatures are most likely to occur, such as areas of coal deposits and associated low thermal conductivities, or areas of thinner crust and associated high basal heat flow. Model temperature data were fitted empirically using five variables, to produce multiple equations that predict temperature to within ± 5°C of the modelled temperatures. This set of equations was used to construct an ArcGIS tool that calculates the temperature at a specified depth, or a depth to a specified temperature, given the necessary map data layers. The appropriate data layers for Australia are being constructed using available datasets including: OZCHEM geochemistry, outcrop geology, SEEBASE™ basin thickness, and combined magnetics and gravity surveys. The ArcGIS geothermal tool will be applied iteratively with layer refinement to identify areas of Australia that warrant more detailed study.

Lescinsky, D. T.; Budd, A. R.; Champion, D. C.; Gerner, E. J.; Kirkby, A. L.

2012-12-01

225

The Occurrence of Pyrrhotite in the Ngawha Geothermal System, New Zealand  

SciTech Connect

The Ngawha geothermal system is low in all sulfide minerals, but in comparison to systems in the Taupo Volcanic Zone it contains more widely distributed pyrrhotite which is currently depositing, mainly in fractures. This reflects the high proportion of vapor in the Ngawha system. Pyrrhotite is most common in the upper part of the reservoir and lower part of the aquitard. The Ngawha pyrrhotite is of monoclinic and monoclinic + hexagonal structure.

Cox, M.E.; Browne, P.R.L.

1995-01-01

226

Final report. Geothermal Energy Program: Information dissemination, public outreach, and technical analysis activities. April 1, 1999 to December 31, 2001. USDOE Grant No. DE-FG01-99-EE35098  

SciTech Connect

This is the final report of the accomplishments of the geothermal energy program: information dissemination, public outreach, and technical analysis activities by the project team consisting of the Geo-Heat Center, Geothermal Resources Council, Geothermal Education Office, Geothermal Energy Association, and the Washington State University Energy Program.

Lund, John W.

2002-03-22

227

Multi-Use Geothermal-Energy System with Augmentation for Enhanced Utilization: A Non-Electric Application of Geothermal Energy in Susanville, California. Final Report.  

National Technical Information Service (NTIS)

A site specific engineering and economic study of multi-use, augmented geothermal space/water heating and cooling systems was completed. The overall benefits to the City of Susanville, in both the public and private sectors, of using low temperature (150 ...

G. K. Olson D. L. Benner-Drury G. R. Cunnington

1979-01-01

228

Methodology of determining the uncertainty in the accessible geothermal resource base of identified hydrothermal convection systems  

USGS Publications Warehouse

In order to quantify the uncertainty of estimates of the geothermal resource base in identified hydrothermal convection systems, a methodology is presented for combining estimates with uncertainties for temperature, area, and thickness of a geothermal reservoir into an estimate of the stored energy with uncertainty. Probability density functions for temperature, area, and thickness are assumed to be triangular in form. In order to calculate the probability distribution function for the stored energy in a single system or in many systems, a computer program for aggregating the input distribution functions using the Monte-Carlo method has been developed. To calculate the probability distribution of stored energy in a single system, an analytical expression is also obtained that is useful for calibrating the Monte Carlo approximation. For the probability distributions of stored energy in a single and in many systems, the central limit approximation is shown to give results ranging from good to poor.

Nathenson, Manuel

1978-01-01

229

Geochemistry of sericite and chlorite in well 14-2 Roosevelt Hot Springs geothermal system and in mineralized hydrothermal systems  

Microsoft Academic Search

Chemical compositions of chlorite and sericite from one production well in the Roosevelt geothermal system have been determined by electron probe methods and compared with compositions of chlorite and sericite from porphyry copper deposits. Modern system sericite and chlorite occur over a depth interval of 2 km and a temperature interval of 250°C.

Ballantyne

1980-01-01

230

Chemical geothermometers and mixing models for geothermal systems  

USGS Publications Warehouse

Qualitative chemical geothermometers utilize anomalous concentrations of various "indicator" elements in groundwaters, streams, soils, and soil gases to outline favorable places to explore for geothermal energy. Some of the qualitative methods, such as the delineation of mercury and helium anomalies in soil gases, do not require the presence of hot springs or fumaroles. However, these techniques may also outline fossil thermal areas that are now cold. Quantitative chemical geothermometers and mixing models can provide information about present probable minimum subsurface temperatures. Interpretation is easiest where several hot or warm springs are present in a given area. At this time the most widely used quantitative chemical geothermometers are silica, Na/K, and Na-K-Ca. ?? 1976.

Fournier, R. O.

1977-01-01

231

Module 7: Geothermal for Agriculture  

NSDL National Science Digital Library

Eastern Iowa Community College provides this learning module to teach students about sources of geothermal energy, geothermal energy production, components of geothermal systems, potential applications of geothermal energy, and a variety of related topics. Users can download a zip file in which they will find a syllabus, student handouts, a quiz, and 58 slide PowerPoint presentation.

2013-11-22

232

The importance of methanotrophic activity in geothermal soils of Pantelleria island (Italy)  

NASA Astrophysics Data System (ADS)

Methane is a major contributor to the greenhouse effect, its atmospheric concentration being more than doubled since the XIX century. Every year 22 Tg of methane are released to the atmosphere from several natural and anthropogenic sources. Natural sources include geothermal/volcanic areas but the estimation of the total methane emission from these areas is currently not well defined since the balance between emission through degassing and microbial oxidation within the soils is not well known. Microbial oxidation in soils contributes globally for about 3-9% to the removal of methane from the atmosphere and recent studies evidenced methanotrophic activity also in soils of volcanic/geothermal areas despite their harsh environmental conditions (high temperatures, low pH and high concentrations of H2S and NH3). Methanotrophs are a diverse group of bacteria that are able to metabolize methane as their only source of carbon and energy and are found within the Alpha and Gamma classes of Proteobacteria and within the phylum Verrucomicrobia. Our purpose was to study the interaction between methanotrophic communities and the methane emitted from the geothermally most active site of Pantelleria island (Italy), Favara Grande, whose total methane emission has been previously estimated in about 2.5 t/a. Laboratory incubation experiments with soil samples from Favara Grande showed methane consumption values of up to 9500 ng g-1 dry soil per hour while soils collected outside the geothermal area consume less than 6 ng g-1 h-1. The maximum consumption was measured in the shallowest part of the soil profile (1-3 cm) and high values (>100 ng g-1 h-1) were maintained up to a depht of 15 cm. Furthermore, the highest consumption was measured at 37°C, and a still recognizable consumption (>20 ng g-1 h-1) at 80°C, with positive correlation with the methane concentration in the incubation atmosphere. These results can be considered a clear evidence of the presence of methanotrophs that were investigated by culturing and culture-independent techniques. The diversity of proteobacterial methanotrophs was investigated by creating a clone library of the amplified methane mono-oxygenase encoding gene, pmoA. Clone sequencing indicates the presence of Gammaproteobacteria in the soils of Favara Grande. Enrichment cultures, on a mineral medium in a CH4-enriched atmosphere, led to the isolation of different strains that were identified as Methylocistis spp., which belong to the Alphaproteobacteria. The presence of Verrucomicrobia was detected by amplification of pmoA gene using newly designed primers. Soils from Favara Grande show therefore the largest spectrum of methanotrophic microorganisms until now detected in a geothermal environment. While the presence of Verrucomicrobia in geothermal soils was predictable due to their thermophilic and acidophilic character, the presence of both Alpha and Gamma proteobacteria was unexpected. Their presence is limited to the shallowest part of the soil were temperatures are lower and is probably favored by a soil pH that is not too low (pH ~5) and their contribution to biological methane oxidation at Pantelleria is significant. Understanding the ecology of methanotrophy in geothermal sites will increase our knowledge of the role of soils in methane emissions in such environments.

D'Alessandro, Walter; Gagliano, Antonina Lisa; Quatrini, Paola; Parello, Francesco

2013-04-01

233

GEOSYS: An X/Motif-based system for analysis and management of geothermal data  

SciTech Connect

The Geothermal Data Management System (GEOSYS) has been developed to allow storage, retrieval, and analysis of the large volume of data associated with a geothermal reservoir, including well drilling data, well log data, production (chemical and flow) data, and geographical data. The system allows the user to display overlays of well locations, faults, and surface features on maps or topographic images. Subsurface cross-sections can be displayed by selecting any two points on the map. Cross sections show subsurface topography together with the projections of wells along the cross section. The structure ofeach individual well can also be displayed in detail. Downhole well logs can be selected, displayed, and expanded to arbitrary scale. Time histories of production data can be displayed for the field and for each well. Data from the Cerro Prieto geothermal field has been used for development and testing of the system. This type of system has been made possible by recent advances in hardware and software technology, and the dramatic reduction in cost of high speed workstations and disk storage. GEOSYS was developed using the X Window System and the OSF/Motif widget set. The X Window System was designed specifically to provide hardware independence for interactive systems based on bit-mapped graphics with a Graphical User Interface (GUI). Systems developed using X run on most modem workstations, and can run across a network with the application being resident on only one computer, but accessible to all others.

Stevens, J.L.; Garg, S.K.; Luu, L.; Barker, T.G.; Pritchett, J.W.; Truesdell, A.H.; Luis Quijano

1993-01-28

234

Enhanced geothermal systems (EGS) with CO2 as heat transmission fluid--A scheme for combining recovery of renewable energy with geologic storage of CO2  

Microsoft Academic Search

It has been suggested that enhanced geothermal systems (EGS) may be operated with supercritical CO instead of water as heat transmission fluid (D.W. Brown, 2000). Such a scheme could combine recovery of geothermal energy with simultaneous geologic storage of CO, a greenhouse gas. At geothermal temperature and pressure conditions of interest, the flow and heat transfer behavior of CO would

K. Pruess; N. Spycher

2009-01-01

235

Strategic optimization of large-scale vertical closed-loop shallow geothermal systems  

NASA Astrophysics Data System (ADS)

Vertical closed-loop geothermal systems or ground source heat pump (GSHP) systems with multiple vertical borehole heat exchangers (BHEs) are attractive technologies that provide heating and cooling to large facilities such as hotels, schools, big office buildings or district heating systems. Currently, the worldwide number of installed systems shows a recurrent increase. By running arrays of multiple BHEs, the energy demand of a given facility is fulfilled by exchanging heat with the ground. Due to practical and technical reasons, square arrays of the BHEs are commonly used and the total energy extraction from the subsurface is accomplished by an equal operation of each BHE. Moreover, standard designing practices disregard the presence of groundwater flow. We present a simulation-optimization approach that is able to regulate the individual operation of multiple BHEs, depending on the given hydro-geothermal conditions. The developed approach optimizes the overall performance of the geothermal system while mitigating the environmental impact. As an example, a synthetic case with a geothermal system using 25 BHEs for supplying a seasonal heating energy demand is defined. The optimization approach is evaluated for finding optimal energy extractions for 15 scenarios with different specific constant groundwater flow velocities. Ground temperature development is simulated using the optimal energy extractions and contrasted against standard application. It is demonstrated that optimized systems always level the ground temperature distribution and generate smaller subsurface temperature changes than non-optimized ones. Mean underground temperature changes within the studied BHE field are between 13% and 24% smaller when the optimized system is used. By applying the optimized energy extraction patterns, the temperature of the heat carrier fluid in the BHE, which controls the overall performance of the system, can also be raised by more than 1 °C.

Hecht-Méndez, J.; de Paly, M.; Beck, M.; Blum, P.; Bayer, P.

2012-04-01

236

Advanced Horizontal Well Recirculation Systems for Geothermal Energy Recovery in Sedimentary Formations  

SciTech Connect

There is increased recognition that geothermal energy resources are more widespread than previously thought, with potential for providing a significant amount of sustainable clean energy worldwide. Recent advances in drilling, completion, and production technology from the oil and gas industry can now be applied to unlock vast new geothermal resources, with some estimates for potential electricity generation from geothermal energy now on the order of 2 million megawatts. Terralog USA, in collaboration with the University of California, Irvine (UCI), are currently investigating advanced design concepts for paired horizontal well recirculation systems, optimally configured for geothermal energy recovery in permeable sedimentary and crystalline formations of varying structure and material properties. This two-year research project, funded by the US Department of Energy, includes combined efforts for: 1) Resource characterization; 2) Small and large scale laboratory investigations; 3) Numerical simulation at both the laboratory and field scale; and 4) Engineering feasibility studies and economic evaluations. The research project is currently in its early stages. This paper summarizes our technical approach and preliminary findings related to potential resources, small-scale laboratory simulation, and supporting numerical simulation efforts.

Mike Bruno; Russell L. Detwiler; Kang Lao; Vahid Serajian; Jean Elkhoury; Julia Diessl; Nicky White

2012-09-30

237

Fracture Characterization in Enhanced Geothermal Systems by Wellbore and Reservoir Analysis  

SciTech Connect

This report highlights the work that was done to characterize fractured geothermal reservoirs using production data. That includes methods that were developed to infer characteristic functions from production data and models that were designed to optimize reinjection scheduling into geothermal reservoirs, based on these characteristic functions. The characterization method provides a robust way of interpreting tracer and flow rate data from fractured reservoirs. The flow-rate data are used to infer the interwell connectivity, which describes how injected fluids are divided between producers in the reservoir. The tracer data are used to find the tracer kernel for each injector-producer connection. The tracer kernel describes the volume and dispersive properties of the interwell flow path. A combination of parametric and nonparametric regression methods were developed to estimate the tracer kernels for situations where data is collected at variable flow-rate or variable injected concentration conditions. The characteristic functions can be used to calibrate thermal transport models, which can in turn be used to predict the productivity of geothermal systems. This predictive model can be used to optimize injection scheduling in a geothermal reservoir, as is illustrated in this report.

Roland N. Horne, Kewen Li, Mohammed Alaskar, Morgan Ames, Carla Co, Egill Juliusson, Lilja Magnusdottir

2012-06-30

238

Modeling of thermodynamic and chemical changes in low-temperature geothermal systems  

SciTech Connect

A method was developed to incorporate the transport of several chemical components into a model of the transport of fluid mass and heat within a geothermal system. It was demonstrated that the use of coupled hydrological, thermal and chemical data allows for the determination of field porosities, amounts and regions of cool recharge into the system as well as field permeabilities and the hot reservoir volume. With the additional information a reliable prediction of the long-term cooling rate can be made.

Spencer, A.L.

1986-12-01

239

Development of an Enhanced Two-Phase Production System at the Geysers Geothermal Field  

SciTech Connect

A method was developed to enhance geothermal steam production from two-phase wells at THE Geysers Geothermal Field. The beneficial result was increased geothermal production that was easily and economically delivered to the power plant.

Steven Enedy

2001-12-14

240

Imperial County Geothermal Development Semi-Annual Report, October 1, 1980-March 31, 1981.  

National Technical Information Service (NTIS)

The current geothermal progress in Imperial County is reported. Three areas are reported: Geothermal Administration, Geothermal Planning, and other Geothermal Activities. Geothermal Administration addresses the status of the Imperial Valley Environmental ...

1981-01-01

241

Critiquing ';pore connectivity' as basis for in situ flow in geothermal systems  

NASA Astrophysics Data System (ADS)

Geothermal system in situ flow systematics derived from detailed examination of grain-scale structures, fabrics, mineral alteration, and pore connectivity may be extremely misleading if/when extrapolated to reservoir-scale flow structure. In oil/gas field clastic reservoir operations, it is standard to assume that small scale studies of flow fabric - notably the Kozeny-Carman and Archie's Law treatments at the grain-scale and well-log/well-bore sampling of formations/reservoirs at the cm-m scale - are adequate to define the reservoir-scale flow properties. In the case of clastic reservoirs, however, a wide range of reservoir-scale data wholly discredits this extrapolation: Well-log data show that grain-scale fracture density fluctuation power scales inversely with spatial frequency k, S(k) ~ 1/k^?, 1.0 < ? < 1.2, 1cycle/km < k < 1cycle/cm; the scaling is a ';universal' feature of well-logs (neutron porosity, sonic velocity, chemical abundance, mass density, resistivity, in many forms of clastic rock and instances of shale bodies, for both horizontal and vertical wells). Grain-scale fracture density correlates with in situ porosity; spatial fluctuations of porosity ? in well-core correlate with spatial fluctuations in the logarithm of well-core permeability, ?? ~ ?log(?) with typical correlation coefficient ~ 85%; a similar relation is observed in consolidating sediments/clays, indicating a generic coupling between fluid pressure and solid deformation at pore sites. In situ macroscopic flow systems are lognormally distributed according to ? ~ ?0 exp(?(?-?0)), ? >>1 an empirical parameter for degree of in situ fracture connectivity; the lognormal distribution applies to well-productivities in US oil fields and NZ geothermal fields, ';frack productivity' in oil/gas shale body reservoirs, ore grade distributions, and trace element abundances. Although presently available evidence for these properties in geothermal reservoirs is limited, there are indications that geothermal system flow essentially obeys the same ';universal' in situ flow rules as does clastic rock: Well-log data from Los Azufres, MX, show power-law scaling S(k) ~ 1/k^?, 1.2 < ? < 1.4, for spatial frequency range 2cycles/km to 0.5cycle/m; higher ?-values are likely due to the relatively fresh nature of geothermal systems; Well-core at Bulalo (PH) and Ohaaki (NZ) show statistically significant spatial correlation, ?? ~ ?log(?) Well productivity at Ohaaki/Ngawha (NZ) and in geothermal systems elsewhere are lognormally distributed; K/Th/U abundances lognormally distributed in Los Azufres well-logs We therefore caution that small-scale evidence for in situ flow fabric in geothermal systems that is interpreted in terms of ';pore connectivity' may in fact not reflect how small-scale chemical processes are integrated into a large-scale geothermal flow structure. Rather such small scale studies should (perhaps) be considered in term of the above flow rules. These flow rules are easily incorporated into standard flow simulation codes, in particular the OPM = Open Porous Media open-source industry-standard flow code. Geochemical transport data relevant to geothermal systems can thus be expected to be well modeled by OPM or equivalent (e.g., INL/LANL) codes.

Kenedi, C. L.; Leary, P.; Malin, P.

2013-12-01

242

The importance of geochemical processes for the sustainability of deep geothermal systems: insights from coupled thermal-hydraulic-chemical modeling of the geothermal system at Bad Blumau, Austria  

NASA Astrophysics Data System (ADS)

We use reactive-transport models patterned after the geothermal system at Bad Blumau, Austria, to track the fate of a fluid during its ascent from the geothermal reservoir to the surface, where it undergoes heat- and CO2-extraction, and during its subsequent reinjection into the deep aquifer. The fluid in the reservoir is in equilibrium with the carbonate-dominated mineralogy of the aquifer rock at local temperature and pressure conditions. Pressure and conductive temperature changes during ascent and descent of the fluid induce changes in mineral solubilities. Subsequent mineral precipitation within the borehole changes the fluid composition and gradually clogs the borehole, thereby obstructing fluid flow. Because different minerals exhibit different solubilities as a function of temperature, the mineral assemblages that precipitate in the production well are distinct from those in the injection well. For instance, if the fluid in the reservoir is saturated in quartz, then the prograde solubility behaviour of quartz favours its precipitation in the production well. Conversely, carbonate minerals tend to precipitate in the injection well owing to their retrograde solubility functions. However, calculating the distribution of mineral phases is complicated by the fact that the precipitation of some minerals is kinetically controlled, such that they may continue to precipitate far into the injection well (e.g. quartz). The strongest modification of the fluid composition and the greatest potential for mineral precipitation occurs during heat extraction, and, in the particular case of Bad Blumau, during the extraction of CO2 at the surface. The extraction of CO2 entails a dramatic increase in the pH and leads to massive precipitation of carbonate minerals. Simulations suggest that, in the worst case, the extraction of CO2 can cause the borehole to be sealed by carbonate minerals within a few weeks. Thus, the use of chemical additives to inhibit carbonate precipitation is imperative in the Bad Blumau system. Furthermore, any modification of the fluid composition caused by mineral precipitation along the fluid's pathway means that the reinjected fluid is no longer in equilibrium with the aquifer rock. Consequently, rock-water interaction and fluid mixing at the base of the injection well drive chemical reactions that cause changes in porosity and permeability of the aquifer, potentially compromising the efficiency of the geothermal system. One concern during geothermal energy production is that of chemical corrosion of the borehole casing. For a range of "what-if" scenarios we explore the effect of corrosion on the fluid composition and on mineral precipitation to identify chemical fingerprints that could be used as corrosion indicators. Once suitable indicators are identified, incipient corrosion could be detected early on during regular chemical monitoring. Corrosion of the casing is typically associated with the release of Fe and H2 into the circulating fluid. However, the implications of this release depend on the local chemical conditions where corrosion occurs. For instance, elevated H2 in the fluid is a corrosion indicator only if it is not involved in subsequent redox reactions. Similarly, low H2 concentrations do not rule out possible corrosion. In general, the interpretation of a fluid or a mineral sample requires the understanding of chemical processes that occur along the flowpath throughout the geothermal system. If direct observations are not possible, then this understanding can only be achieved through numerical simulations that integrate and couple fluid flow, heat transport and chemical reactions within one theoretical framework. Our simulations demonstrate that these models are useful for quantifying the impact and minimizing the risk that chemical reactions may have on the productivity and sustainability of a geothermal system.

Alt-Epping, P.; Waber, H. N.; Eichinger, L.; Diamond, L. W.

2009-04-01

243

Gas chemistry, boiling and phase segregation in a geothermal system, Hellisheidi, Iceland  

NASA Astrophysics Data System (ADS)

The geochemistry of aquifer fluids of the Hellisheidi geothermal system, southwest Iceland, was studied. Based on samples of vapor and liquid from well discharge fluids, the aquifer fluid compositions at the depth of the geothermal system were reconstructed taking into account the highly variable degree of excess well discharge enthalpy, where the enthalpy of the discharge is significantly higher than that of vapor-saturated liquid at the measured aquifer temperature. Decreasing concentrations of non-volatile components such as Si in the total well discharge suggest that the main cause of elevated discharge enthalpies is liquid-vapor phase segregation, i.e. the retention of liquid in the aquifer rock due to its adhesion onto mineral surfaces. Moreover, the slightly lower than equilibrium calculated concentrations of H2 and H2S in some of the hottest and highest-enthalpy wells is considered to be caused by conductive heat transfer from the rocks to the fluids. Alternatively, the cause may lie in the selection of the phase segregation conditions. The calculated concentrations of volatile species in the aquifer fluid are very sensitive to the assumed phase segregation conditions while non-volatiles are not greatly affected by this model parameter. In general, the level of uncertainty does not contradict previous findings of a close approach to fluid-mineral equilibrium at aquifer temperatures above 250 °C. The CO2 concentrations were observed to fall below equilibrium with respect to the most likely mineral buffers, suggesting a possible source control. Elevated H2 concentrations indicate a small equilibrium vapor fraction in aquifer fluids (˜0.2% by mass or ˜3% by volume). Previous conceptual models of the Hengill volcanic area (e.g. Bödvarsson et al., 1990) have implied a central magmatic heat source underlying the Hengill central volcano. Instead, a new conceptual model of the Hellisheidi system is proposed that features two main regions of fluid upflow heated by a complex of dikes and sills associated with an eruptive fissure active during the Holocene.

Scott, Samuel; Gunnarsson, Ingvi; Arnórsson, Stefán; Stefánsson, Andri

2014-01-01

244

Energy Returned On Investment of Engineered Geothermal Systems Annual Report FY2011  

SciTech Connect

Energy Return On Investment (EROI) is an important figure of merit for assessing the viability of energy alternatives. For geothermal electric power generation, EROI is determined by the electricity delivered to the consumer compared to the energy consumed to construct, operate, and decommission the facility. Critical factors in determining the EROI of Engineered Geothermal Systems (EGS) are examined in this work. These include the input energy embodied into the system. The embodied energy includes the energy contained in the materials, as well as, that consumed in each stage of manufacturing from mining the raw materials to assembling the finished plant. Also critical are the system boundaries and value of the energy - heat is not as valuable as electrical energy.

Mansure, A.J.

2011-12-31

245

Selection of working fluids for a novel low-temperature geothermally-powered ORC based cogeneration system  

Microsoft Academic Search

A novel cogeneration system driven by low-temperature geothermal sources was investigated in this study. This system consists of a low-temperature geothermally-powered organic Rankine cycle (ORC) subsystem, an intermediate heat exchanger and a commercial R134a-based heat pump subsystem. The main purpose is to identify appropriate fluids which may yield high PPR (the ratio of power produced by the power generation subsystem

T. Guo; H. X. Wang; S. J. Zhang

2011-01-01

246

New Mexican geothermal development  

Microsoft Academic Search

New Mexico has more than 300 known thermal springs and wells, most located within the Rio Grande Rift, a north-south trending geological system that runs through the state. In the 1970's, state and federal governments took an active interest in geothermal energy in New Mexico. The studies identified 21 low-temperature sites in the state with the highest potential for commercial

1987-01-01

247

IGA: International Geothermal Association  

NSDL National Science Digital Library

The International Geothermal Association's (IGA) goal is "to encourage research, development, and utilization of geothermal resources worldwide through the compilation, publication, and dissemination of scientific and technical data and information." The website offers a multitude of information about geothermal energy around the world. Students can find educational resources about the history, nature, classification, utilization, and exploration of geothermal systems. Through an interactive map, users can find data on geothermal energy. Researchers can discover journals and upcoming conferences. Visitors can also learn how to take part in the IGA panel and discussion group.

248

Modeling Hydro-Mechanical Reservoir Stimulation for Geothermal Systems  

NASA Astrophysics Data System (ADS)

Several geothermal EGS projects are under development worldwide. As such the Coso project in the US and the Soultz project in Europe intend to produce electricity from circulating fluids in hot fracture rock. Improvement of the reservoir conditions by hydraulic stimulation and minimizing the seismic risk represents now a primary challenge to enable economic operation and future extension. In this context, the new HEX-S code has been developed to simulate the transient hydro-mechanical response of the rock matrix to massive hydraulic injections. The present paper describes the modeling results of the Soultz stimulation from 2003 and 2004 and the analysis of the situation in Coso. Maximum flow rates of 60 l/s have been used, triggering above 30'000 microseismic events. The transient numerical simulation intends to obtain a match of both, the microseismic and the hydraulic behavior. Different model calculations demonstrate the capabilities of our new approach. It is noteworthy that the modeling became possible only due to the excellent data quality at the Soultz project. The results demonstrate that simulations based on solid physical ground can reveal the complex reservoir behavior during hydraulic stimulation. The use of HEX-S also provides perspectives for future developments such as design calculations that enable optimizing cost-intensive hydraulic stimulations before hand.

Kohl, T.; Mégel, T.

2005-12-01

249

Modeling of a Liquid Phase Geothermal Doublet System at Regina, Saskatchewan, Canada  

NASA Astrophysics Data System (ADS)

The paper describes a computer-mathematical model used to analyze the nature of the subsurface temperature disturbance that results from extraction of hot liquid from a geothermal production well with concurrent injection of cooled tailings water in a nearby disposal well. The model was designed specifically to determine, at an early stage of development, an appropriate well spacing for the sedimentary-basin geothermal project at Regina, Canada. Assumptions include an infinite horizontal confined aquifer with uniform thickness and a finely dispersed pore system. The mathematical model is based on an energy balance equation that combines Darcy's law, Fourier's law, and the change in heat content of an element within the active zone of the aquifer. The numerical model is developed by means of the integrated finite difference technique. Short computer run times are achieved through the use of symmetry, an expanding grid system, and the use of the Theis solution. Investigation of model sensitivity shows the model to be sensitive to such factors as interwell distance, pumping rates, porosity, and aquifer thickness, but quite insensitive to hydraulic conductivity and storativity. Sample results are given for Regin aquifers undergoing both continuous and seasonal pumping. Isotherm maps show that the temperature disturbance evolves with time from a cooled, circular area around the injection well to a strongly noncircular pattern with a protrusion of cooled water extending toward the production well. The model is used to predict time of thermal breakthrough for Regina aquifers using different pumping rates and interwell distances. Temperature histories for continuous pumping show that after thermal breakthrough, the produced water undergoes a slight decline of temperature over a considerable time span. For the withdrawal of equal volumes of fluid, the temperature disturbance around the disposal well is spread over a slightly larger area for the seasonal pumping case compared to continuous pumping. The thermal front is broader for the seasonal case because of the longer period of elapsed time during which thermal conduction occurs. For seasonal operations, thermal breakthrough will occur after less water has been pumped and there is a more gradual decline in the temperature of the production well after thermal breakthrough.

Hutchence, K.; Weston, J. H.; Law, A. G.; Vigrass, L. W.; Jones, F. W.

1986-09-01

250

Finite Element Modeling for Geothermal Resource Exploration  

NASA Astrophysics Data System (ADS)

Recently there has been an increased interest in developing geothermal resources to satisfy growing energy needs. Hence, there is a need to accurately locate and characterize viable geothermal systems. Geothermal resources often exhibit anomalously high electrical conductivities and elevated ground surface temperatures. In this project, we gather temperature, temperature gradient, direct current resistivity, and spectral induced polarization data over a geothermally active area. Incorporating all these data types for geothermal resource exploration can reduce ambiguity in the geologic model and increase discovery success rates. However, joint inversion of different survey types for multiple physical parameters is not yet routine. We have utilized COMSOL Multiphysics, a commercially available finite element modeling software package, to create and evaluate complex geological and geophysical models which include all pertinent rock properties. We combine the geophysical data with geologic knowledge to create a robust model of the geothermal reservoir. We start with existing geologic data and resistivity inversion results to build a base model in COMSOL. Then we synthesize our surveys with the finite element method and compare the results with the field data. The model is then modified to more accurately describe the field data. This process may be repeated multiple times with the user’s geologic knowledge guiding the process. The end result is a geologic model of the geothermal area which satisfies all geological and geophysical field data. This will reduce the risks associated with geothermal prospecting.

Quilty, J.; Cox, L. H.; Elkins, B.

2010-12-01

251

Underground Mine Water Heating and Cooling Using Geothermal Heat Pump Systems  

SciTech Connect

In many regions of the world, flooded mines are a potentially cost-effective option for heating and cooling using geothermal heat pump systems. For example, a single coal seam in Pennsylvania, West Virginia, and Ohio contains 5.1 x 1012 L of water. The growing volume of water discharging from this one coal seam totals 380,000 L/min, which could theoretically heat and cool 20,000 homes. Using the water stored in the mines would conservatively extend this option to an order of magnitude more sites. Based on current energy prices, geothermal heat pump systems using mine water could reduce annual costs for heating by 67% and cooling by 50% over conventional methods (natural gas or heating oil and standard air conditioning).

Watzlaf, G.R.; Ackman, T.E.

2006-03-01

252

Applications of fractured continuum model to enhanced geothermal system heat extraction problems.  

PubMed

This paper describes the applications of the fractured continuum model to the different enhanced geothermal systems reservoir conditions. The capability of the fractured continuum model to generate fracture characteristics expected in enhanced geothermal systems reservoir environments are demonstrated for single and multiple sets of fractures. Fracture characteristics are defined by fracture strike, dip, spacing, and aperture. The paper demonstrates how the fractured continuum model can be extended to represent continuous fractured features, such as long fractures, and the conditions in which the fracture density varies within the different depth intervals. Simulations of heat transport using different fracture settings were compared with regard to their heat extraction effectiveness. The best heat extraction was obtained in the case when fractures were horizontal. A conventional heat extraction scheme with vertical wells was compared to an alternative scheme with horizontal wells. The heat extraction with the horizontal wells was significantly better than with the vertical wells when the injector was at the bottom. PMID:24600552

Kalinina, Elena A; Klise, Katherine A; McKenna, Sean A; Hadgu, Teklu; Lowry, Thomas S

2014-01-01

253

On-line corrosion monitoring in geothermal district heating systems. II. Localized corrosion  

Microsoft Academic Search

Corrosion monitoring in district heating systems has traditionally been performed by using off-line methods, such as weight loss. The disadvantage is that the method is very slow, especially in low-corrosive environments, and that it only provides information about the past corrosion (accumulated over period of time). The purpose of the work is to test on-line monitoring methods in geothermal hot

S. Richter; R. I. Thorarinsdottir; F. Jonsdottir

2007-01-01

254

A re-evaluation of the Moyuta geothermal system, Southern Guatemala  

Microsoft Academic Search

Chemical and isotopic data from four fumarole sites combined with prefeasibility assessments obtained in the 1970s have resulted in a re-evaluation of the Moyuta geothermal system. Moyuta consists of an east-west trending complex of Quaternary andesite\\/dacite domes and flows cut by north-trending faults. Areas of fumaroles, acid springs, and bicarbonate-rich thermal springs flank the north and south sides of the

F. Goff; A. Adams; P. E. Trujillo; D. Counce; C. Janik; L. Fahlquist; A. Roldan; M. Revolorio

1991-01-01

255

Fluids and parameters optimization for a novel cogeneration system driven by low-temperature geothermal sources  

Microsoft Academic Search

A novel cogeneration system was proposed and techno-economically investigated, consisting of a low-temperature geothermally-powered organic Rankine cycle (ORC) subsystem, an intermediate heat exchanger subsystem and a heat pump subsystem. The main purpose is to identify suitable working fluids (among 27 fluids with boiling point temperature ranging from ?47.69 to 47.59°C) and optimized cycle parameters for the ORC-based power generation subsystem.

T. Guo; H. X. Wang; S. J. Zhang

2011-01-01

256

Geothermal Energy.  

ERIC Educational Resources Information Center

Described are the origin and nature of geothermal energy. Included is the history of its development as an energy source, technological considerations affecting its development as an energy source, its environmental effects, economic considerations, and future prospects of development in this field. Basic system diagrams of the operation of a…

Eaton, William W.

257

COTHERM: Numerical modeling of the deep roots of volcanic geothermal systems  

NASA Astrophysics Data System (ADS)

We report numerical simulations of the transient evolution of fluid flow and heat transport in high-enthalpy geothermal systems around cooling intrusions, including the deep, 'supercritical' roots. We employ the CSMP++ fluid flow and heat transport code, and analyze the temperature, pressure, phase state distribution etc. during the whole lifetime of a geothermal system. Such simulations are of high relevance to projects like the Iceland Deep Drilling Project, which aim to dramatically improve the economics of geothermal power production by tapping such 'supercritical' reservoirs. We study the effects of the depth of the intrusion, the system-scale permeability and the permeability change across the brittle-ductile transition. While previous studies have commonly adopted a temperature-dependent parameterization, with permeability decreasing in a log-linear fashion at temperatures above 360° C, this study explores a variety of different potential temperature dependencies of permeability and their effects on model results. These effects are large and namely affect the thickness of the conductive boundary layer, which impacts the overall rate of cooling of the intrusion.

Scott, Samuel; Weis, Philipp; Driesner, Thomas

2014-05-01

258

Simulation of water-rock interaction in the Yellowstone geothermal system using TOUGHREACT  

SciTech Connect

The Yellowstone geothermal system provides an ideal opportunity to test the ability of reactive transport models to simulate the chemical and hydrological effects of water-rock interaction. Previous studies of the Yellowstone geothermal system have characterized water-rock interaction through analysis of rocks and fluids obtained from both surface and downhole samples. Fluid chemistry, rock mineralogy, permeability, porosity, and thermal data obtained from the Y-8 borehole in Upper Geyser Basin were used to constrain a series of reactive transport simulations of the Yellowstone geothermal system using TOUGHREACT. Three distinct stratigraphic units were encountered in the 153.4 m deep Y-8 drill core: volcaniclastic sandstone, perlitic rhyolitic lava, and nonwelded pumiceous tuff. The main alteration phases identified in the Y-8 core samples include clay minerals, zeolites, silica polymorphs, adularia, and calcite. Temperatures observed in the Y-8 borehole increase with depth from sub-boiling conditions at the surface to a maximum of 169.8 C at a depth of 104.1 m, with near-isothermal conditions persisting down to the well bottom. 1-D models of the Y-8 core hole were constructed to simulate the observed alteration mineral assemblage given the initial rock mineralogy and observed fluid chemistry and temperatures. Preliminary simulations involving the perlitic rhyolitic lava unit are consistent with the observed alteration of rhyolitic glass to form celadonite.

Dobson, Patrick F.; Salah, Sonia; Spycher, Nicolas; Sonnenthal, Eric L.

2003-04-28

259

Simulation of water-rock interaction in the yellowstone geothermal system using TOUGHREACT  

SciTech Connect

The Yellowstone geothermal system provides an ideal opportunity to test the ability of reactive transport models to accurately simulate water-rock interaction. Previous studies of the Yellowstone geothermal system have characterized water-rock interaction through analysis of rocks and fluids obtained from both surface and downhole samples. Fluid chemistry, rock mineralogy, permeability, porosity, and thermal data obtained from the Y-8 borehole in Upper Geyser Basin were used to constrain a series of reactive transport simulations of the Yellowstone geothermal system using TOUGHREACT. Three distinct stratigraphic units were encountered in the 153.4 m deep Y-8 drill core: volcaniclastic sandstone, perlitic rhyolitic lava, and nonwelded pumiceous tuff. The main alteration phases identified in the Y-8 core samples include clay minerals, zeolites, silica polymorphs, adularia, and calcite. Temperatures observed in the Y-8 borehole increase with depth from sub-boiling conditions at the surface to a maximum of 169.8 C at a depth of 104.1 m, with near-isothermal conditions persisting down to the well bottom. 1-D models of the Y-8 core hole were constructed to determine if TOUGHREACT could accurately predict the observed alteration mineral assemblage given the initial rock mineralogy and observed fluid chemistry and temperatures. Preliminary simulations involving the perlitic rhyolitic lava unit are consistent with the observed alteration of rhyolitic glass to form celadonite.

Dobson, P.F.; Salah, S.; Spycher, N.; Sonnenthal, E.

2003-04-28

260

Development of a new activity model for complex mixed-salt solutions from ambient to geothermal conditions  

NASA Astrophysics Data System (ADS)

Geochemical modeling of fluid-rock interaction in geothermal environments is a demanding task because of the prevalent high temperatures, pressures and salinities. Solution speciation, mineral compositions and assemblages as well as gas compositions are typically computed from multicomponent-multiphase thermodynamic models for standard state properties and activities or fugacities. In concentrated aqueous solutions, the Pitzer model (Pitzer, 1973) is the standard approach for computing solute species and solvent activities. An alternative model is the extended universal quasichemical (EUNIQUAC) model (Thomsen & Rasmussen, 1996). The Pitzer model is based on a virial expansion of the osmotic pressure. For complex multi-electrolyte solutions comprising several dozens of solute species, the number of empiric parameters for the Pitzer model can easily excceed several hundreds. The EUNIQUAC model needs less than a quarter of the empiric parameters required for the Pitzer model. EUNIQUAC is based on more recent theoretical approaches to the statistical mechanical treatment of solutions. A disadvantage of the EUNIQUAC model is that it gives a less accurate representation of the experimental data. A disadvantage of both models is that they are typically only parameterized along the vapor-pressure saturation curve, which considerably restricts their range of application at geothermal conditions. We developed a modification of the EUNIQUAC model (termed ELVIS) which preserves the non-electrostatic framework of EUNIQUAC, but accounts better for electrostatic interactions. ELVIS needs significantly fewer parameters than the Pitzer model, but yields comparably accurate representation of experimental data. Unlike the EUNIQUAC and Pitzer models, the ELVIS parameters are formulated both in terms of temperature and pressure dependence. First results of calibrating the ELVIS model to experimental data of the H2O-NaCl and H2O-CaCl2 systems over wide ranges in temperature, pressure and composition are presented.

Hingerl, F. F.; Wagner, T.; Kulik, D. A.; Kosakowski, G.; Driesner, T.

2012-04-01

261

Optimization of Integrated Reservoir, Wellbore, and Power Plant Models for Enhanced Geothermal Systems  

NASA Astrophysics Data System (ADS)

Geothermal energy has the potential to become a substantially greater contributor to the U.S. energy market. An adequate investment in Enhanced Geothermal Systems (EGS) technology will be necessary in order to realize the potential of geothermal energy. This study presents an optimization of a waterbased Enhanced Geothermal System (EGS) modeled for AltaRock Energy's Newberry EGS Demonstration location. The optimization successfully integrates all three components of the geothermal system: (1) the present wellbore design, (2) the reservoir design, and (3) the surface plant design. Since the Newberry EGS Demonstration will use an existing well (NWG 55-29), there is no optimization of the wellbore design, and the aim of the study for this component is to replicate the present wellbore conditions and design. An in-house wellbore model is used to accurately reflect the temperature and pressure changes that occur in the wellbore fluid and the surrounding casing, cement, and earth during injection and production. For the reservoir design, the existing conditions, such as temperature and pressure at depth and rock density, are incorporated into the model, and several design variables are investigated. The engineered reservoir is modeled using the reservoir simulator TOUGH2 while using the graphical interface PetraSim for visualization. Several fracture networks are investigated with the goal of determining which fracture network yields the greatest electrical output when optimized jointly with the surface plant. A topological optimization of the surface is completed to determine what type of power plant is best suited for this location, and a parametric optimization of the surface plant is completed to determine the optimal operating conditions. The conditions present at the Newberry, Oregon EGS project site are the basis for this optimization. The subsurface conditions are favorable for the production of electricity from geothermal energy with rock temperatures exceeding 300°C at a well depth of 3 km. This research was completed in collaboration with AltaRock Energy, which has provided our research group with data from the Newberry well. The purpose of this thesis is to determine the optimal conditions for operating an Enhanced Geothermal System for the production of electricity at Newberry. It was determined that a fracture network consisting of five fractured zones carrying 15 kg/s of fluid is the best reservoir design out of those investigated in this study. Also, it was found that 100 m spacing between the fractured zones should be implemented as opposed to only 50 m of spacing. A double-flash steam power plant provides the best method of utilization of the geothermal fluid. For the maximum amount of electricity generation over the 30-year operating lifetime, the cyclone separator should operate at 205°C and the flash vessel should operate at 125°C.

Peluchette, Jason

262

Recent drilling activities at the earth power resources Tuscarora geothermal power project's hot sulphur springs lease area.  

SciTech Connect

Earth Power Resources, Inc. recently completed a combined rotary/core hole to a depth of 3,813 feet at it's Hot Sulphur Springs Tuscarora Geothermal Power Project Lease Area located 70-miles north of Elko, Nevada. Previous geothermal exploration data were combined with geologic mapping and newly acquired seismic-reflection data to identify a northerly tending horst-graben structure approximately 2,000 feet wide by at least 6,000 feet long with up to 1,700 feet of vertical offset. The well (HSS-2) was successfully drilled through a shallow thick sequence of altered Tertiary Volcanic where previous exploration wells had severe hole-caving problems. The ''tight-hole'' drilling problems were reduced using drilling fluids consisting of Polymer-based mud mixed with 2% Potassium Chloride (KCl) to reduce Smectite-type clay swelling problems. Core from the 330 F fractured geothermal reservoir system at depths of 2,950 feet indicated 30% Smectite type clays existed in a fault-gouge zone where total loss of circulation occurred during coring. Smectite-type clays are not typically expected at temperatures above 300 F. The fracture zone at 2,950 feet exhibited a skin-damage during injection testing suggesting that the drilling fluids may have caused clay swelling and subsequent geothermal reservoir formation damage. The recent well drilling experiences indicate that drilling problems in the shallow clays at Hot Sulphur Springs can be reduced. In addition, average penetration rates through the caprock system can be on the order of 25 to 35 feet per hour. This information has greatly reduced the original estimated well costs that were based on previous exploration drilling efforts. Successful production formation drilling will depend on finding drilling fluids that will not cause formation damage in the Smectite-rich fractured geothermal reservoir system. Information obtained at Hot Sulphur Springs may apply to other geothermal systems developed in volcanic settings.

Goranson, Colin

2005-03-01

263

Insights From Laboratory Experiments On Simulated Faults With Application To Fracture Evolution In Geothermal Systems  

SciTech Connect

Laboratory experiments provide a wealth of information related to mechanics of fracture initiation, fracture propagation processes, factors influencing fault strength, and spatio-temporal evolution of fracture properties. Much of the existing literature reports on laboratory studies involving a coupling of thermal, hydraulic, mechanical, and/or chemical processes. As these processes operate within subsurface environments exploited for their energy resource, laboratory results provide insights into factors influencing the mechanical and hydraulic properties of geothermal systems. I report on laboratory observations of strength and fluid transport properties during deformation of simulated faults. The results show systematic trends that vary with stress state, deformation rate, thermal conditions, fluid content, and rock composition. When related to geophysical and geologic measurements obtained from engineered geothermal systems (e.g. microseismicity, wellbore studies, tracer analysis), laboratory results provide a means by which the evolving thermal reservoir can be interpreted in terms of physico-chemical processes. For example, estimates of energy release and microearthquake locations from seismic moment tensor analysis can be related to strength variations observed from friction experiments. Such correlations between laboratory and field data allow for better interpretations about the evolving mechanical and fluid transport properties in the geothermal reservoir – ultimately leading to improvements in managing the resource.

Stephen L. Karner, Ph.D

2006-06-01

264

Simulation of Enhanced Geothermal Systems: A Benchmarking and Code Intercomparison Study  

SciTech Connect

Numerical simulation codes have become critical tools for understanding complex geologic processes, as applied to technology assessment, system design, monitoring, and operational guidance. Recently the need for quantitatively evaluating coupled Thermodynamic, Hydrologic, geoMechanical, and geoChemical (THMC) processes has grown, driven by new applications such as geologic sequestration of greenhouse gases and development of unconventional energy sources. Here we focus on Enhanced Geothermal Systems (EGS), which are man-made geothermal reservoirs created where hot rock exists but there is insufficient natural permeability and/or pore fluids to allow efficient energy extraction. In an EGS, carefully controlled subsurface fluid injection is performed to enhance the permeability of pre-existing fractures, which facilitates fluid circulation and heat transport. EGS technologies are relatively new, and pose significant simulation challenges. To become a trusted analytical tool for EGS, numerical simulation codes must be tested to demonstrate that they adequately represent the coupled THMC processes of concern. This presentation describes the approach and status of a benchmarking and code intercomparison effort currently underway, supported by the U. S. Department of Energy’s Geothermal Technologies Program. This study is being closely coordinated with a parallel international effort sponsored by the International Partnership for Geothermal Technology (IPGT). We have defined an extensive suite of benchmark problems, test cases, and challenge problems, ranging in complexity and difficulty, and a number of modeling teams are applying various simulation tools to these problems. The descriptions of the problems and modeling results are being compiled using the Velo framework, a scientific workflow and data management environment accessible through a simple web-based interface.

Scheibe, Timothy D.; White, Mark D.; White, Signe K.; Sivaramakrishnan, Chandrika; Purohit, Sumit; Black, Gary D.; Podgorney, Robert; Boyd, Lauren W.; Phillips, Benjamin R.

2013-06-30

265

Geothermal reconnaissance of the Marmara Sea region (NW Turkey): surface heat flow density in an area of active continental extension  

Microsoft Academic Search

Northwestern Anatolia is an area of significant neotectonic activity. The Northern Anatolian Fault splits into different branches and the tectonic regime changes from translation to a combination of extension and translation. High seismicity as well as frequent and in places large hot springs are related to these tectonic features. The present study aims at characterising the geothermal situation of this

Martin Pfister; Ladislaus Rybach; Sakir Simsek

1998-01-01

266

Current California legislative and regulatory activity impacting geothermal hydrothermal commercialization: monitoring report No. 2. Report No. 1020  

SciTech Connect

The progress of four bills relating to geothermal energy is reported. The current regulatory activities of the California Energy Commission, the Lake County Planning Commission/Lake County Air Pollution Control District, the Governor's Office of Planning and Research, the State Lands' Commission, and the California Public Utilities Commission are reviewed. (MHR)

Not Available

1980-04-20

267

Geothermal systems within the Mammoth Corridor in Yellowstone National Park and the adjacent Corwin Springs KGRA  

USGS Publications Warehouse

A study of potential impacts of geothermal development in the Corwin Springs KGRA north of Yellowstone Park on thermal springs within the Park is being conducted by the U.S. Geological Survey. Thermal waters in the KGRA and at Mammoth Hot Springs, located 13 km inside the Park boundary, are high in bicarbonate and sulfate and are actively depositing travertine. These similarities and the existence of numerous regional-scale structural and stratigraphic features that could provide conduits for fluid flow at depth indicate a possible cause for concern. The objectives of this study include delineations of any hydrologic connections between these thermal waters, the level of impact of geothermal development in the event of such connections, and mitigation measures to minimize or eliminate adverse impacts. The study involves a number of geochemical, geophysical, geologic, and hydrologic techniques, but does not include any test drilling. Preliminary results suggest that thermal waters at Bear Creek Springs may contain a component of water derived from Mammoth but that thermal waters at La Duke Hot Spring do not. The total rate of thermal water that discharges in the area proposed for geothermal development (near La Duke) has been determined; restricting the net production of thermal water to rates less than this total could provide a satisfactory margin of safety for development.

Sorey, Michael; Colvard, Elizabeth; Sturchio, N. C.

1990-01-01

268

Geothermal Energy.  

ERIC Educational Resources Information Center

An introduction to geothermal energy is provided in this discussion of: (1) how a geothermal reservoir works; (2) how to find geothermal energy; (3) where it is located; (4) electric power generation using geothermal energy; (5) use of geothermal energy as a direct source of heat; (6) geopressured reservoirs; (7) environmental effects; (8)…

Conservation and Renewable Energy Inquiry and Referral Service (DOE), Silver Spring, MD.

269

Geothermal energy: 1992 program overview  

SciTech Connect

Geothermal energy is described in general terms with drawings illustrating the technology. A map of known and potential geothermal resources in the US is included. The 1992 program activities are described briefly. (MHR)

Not Available

1993-04-01

270

Review of international geothermal activities and assessment of US industry opportunities: Summary report  

SciTech Connect

This report summarizes a study initiated to review and assess international developments in the geothermal energy field and to define business opportunities for the US geothermal industry. The report establishes data bases on the status of worldwide geothermal development and the competitiveness of US industry. Other factors identified include existing legislation, tax incentives, and government institutions or agencies and private sector organizations that promote geothermal exports. Based on the initial search of 177 countries and geographic entities, 71 countries and areas were selected as the most likely targets for the expansion of the geothermal industry internationally. The study then determined to what extent their geothermal resource had been developed, what countries had aided or participated in this development, and what plans existed for future development. Data on the energy, economic, and financial situations were gathered.

Not Available

1987-08-01

271

Review of international geothermal activities and assessment of US industry opportunities: Final report  

SciTech Connect

This study was initiated to review and assess international developments in the geothermal energy field and to define business opportunities for the US geothermal industry. The report establishes data bases on the status of worldwide geothermal development and the competitiveness of US industry. Other factors identified include existing legislation, tax incentives, and government institutions or agencies and private sector organizations that promote geothermal exports. Based on the initial search of 177 countries and geographic entities, 71 countries and areas were selected as the most likely targets for the expansion of the geothermal industry internationally. The study then determined to what extent their geothermal resource had been developed, what countries had aided or participated in this development, and what plans existed for future development. Data on the energy, economic, and financial situations were gathered.

Not Available

1987-08-01

272

Pumpernickel Valley Geothermal Project Thermal Gradient Wells  

SciTech Connect

The Pumpernickel Valley geothermal project area is located near the eastern edge of the Sonoma Range and is positioned within the structurally complex Winnemucca fold and thrust belt of north-central Nevada. A series of approximately north-northeast-striking faults related to the Basin and Range tectonics are superimposed on the earlier structures within the project area, and are responsible for the final overall geometry and distribution of the pre-existing structural features on the property. Two of these faults, the Pumpernickel Valley fault and Edna Mountain fault, are range-bounding and display numerous characteristics typical of strike-slip fault systems. These characteristics, when combined with geophysical data from Shore (2005), indicate the presence of a pull-apart basin, formed within the releasing bend of the Pumpernickel Valley – Edna Mountain fault system. A substantial body of evidence exists, in the form of available geothermal, geological and geophysical information, to suggest that the property and the pull-apart basin host a structurally controlled, extensive geothermal field. The most evident manifestations of the geothermal activity in the valley are two areas with hot springs, seepages, and wet ground/vegetation anomalies near the Pumpernickel Valley fault, which indicate that the fault focuses the fluid up-flow. There has not been any geothermal production from the Pumpernickel Valley area, but it was the focus of a limited exploration effort by Magma Power Company. In 1974, the company drilled one exploration/temperature gradient borehole east of the Pumpernickel Valley fault and recorded a thermal gradient of 160oC/km. The 1982 temperature data from five unrelated mineral exploration holes to the north of the Magma well indicated geothermal gradients in a range from 66 to 249oC/km for wells west of the fault, and ~283oC/km in a well next to the fault. In 2005, Nevada Geothermal Power Company drilled four geothermal gradient wells, PVTG-1, -2, -3, and -4, and all four encountered geothermal fluids. The holes provided valuable water geochemistry, supporting the geothermometry results obtained from the hot springs and Magma well. The temperature data gathered from all the wells clearly indicates the presence of a major plume of thermal water centered on the Pumpernickel Valley fault, and suggests that the main plume is controlled, at least in part, by flow from this fault system. The temperature data also defines the geothermal resource with gradients >100oC/km, which covers an area a minimum of 8 km2. Structural blocks, down dropped with respect to the Pumpernickel Valley fault, may define an immediate reservoir. The geothermal system almost certainly continues beyond the recently drilled holes and might be open to the east and south, whereas the heat source responsible for the temperatures associated with this plume has not been intersected and must be at a depth greater than 920 meters (depth of the deepest well – Magma well). The geological and structural setting and other characteristics of the Pumpernickel Valley geothermal project area are markedly similar to the portions of the nearby Dixie Valley geothermal field. These similarities include, among others, the numerous, unexposed en echelon faults and large-scale pull-apart structure, which in Dixie Valley may host part of the geothermal field. The Pumpernickel Valley project area, for the majority of which Nevada Geothermal Power Company has geothermal rights, represents a geothermal site with a potential for the discovery of a relatively high temperature reservoir suitable for electric power production. Among locations not previously identified as having high geothermal potential, Pumpernickel Valley has been ranked as one of four sites with the highest potential for electrical power production in Nevada (Shevenell and Garside, 2003). Richards and Blackwell (2002) estimated the total heat loss and the preliminary production capacity for the entire Pumpernickel Valley geothermal system to be at 35MW. A more conservative estimate, for

Z. Adam Szybinski

2006-01-01

273

Mass variation in outcome to high production activity in Kamojang Geothermal Field, Indonesia: A reservoir monitoring with relative and absolute gravimetry  

NASA Astrophysics Data System (ADS)

The Kamojang Geothermal Field (KGF) is a typical vapor dominated hydrothermal system in west Java, Indonesia. This geothermal field is the oldest exploited geothermal field in Indonesia. From 1983 to 2005, more than 160 million tons of steam has been exploited from the KGF and more than 30 million tons of condensed water and river water were injected to the reservoir system. Regarding to the electricity demand, installed capacity of KGF increased from 30 MWe to 140 MWe in 1987 and 200 MWe in 2007. Mass variation in the geothermal reservoir can be measured by using the map of the gravity changes. Gravity changes observed in the KGF between 1999 and 2005 at 51 benchmarks are interpreted in terms of a change of mass. Concerning to the production mass increase, gravity changes also observed between 1999 and 2008 at 30 benchmarks. The recent gravity measurement was conducted using absolute gravimeter in 2009 and 2010 at 12 gravity benchmarks. Mass variation in the reservoir was caused by production and injection activities. Mass variation in KGF from 1999 to 2005 is about -3.34 Mt/year while is about -3.78 Mt/year from 1999 to 2008. Another period between 2009 and 2010, mass variation decreased about -8.24 Mt. According to the history of production and injection, natural recharge to the KGF's reservoir is estimated at about 2.77 Mt/year from 1999 to 2005 and 2.75 Mt/year from 1999 to 2008. Between 2009 and 2010, KGF has a bigger mass deficiency rate throughout 200 MWe maintain production.

Sofyan, Y.; Kamah, Y.; Nishijima, J.; Fujimitsu, Y.; Ehara, S.; Fukuda, Y.; Taniguchi, M.

2011-11-01

274

Water/rock interaction in the K?z?lcahamam Geothermal Field, Galatian Volcanic Province (Turkey): a modelling study of a geothermal system for reinjection well locations  

NASA Astrophysics Data System (ADS)

The K?z?lcahamam geothermal field is emplaced in Tertiary-aged volcanic units 70 km NW of Ankara (Turkey). Data for this low-temperature (74-86°C) geothermal field regarding the fracture zone system were obtained from surface manifestations (hot springs, alteration zones), five exploration wells (MTA-2, -3, -4, -5, -6) and two production wells (KHD-1, MTA-1). The K?z?lcahamam reservoir developed along the K?z?lcahamam fault zone and so the production wells (180-1556 m) effect each other due to their limited separation. Meteoric water enters from a recharge area NE of K?z?lcahamam, circulates and gains heat through the fault zone, and discharges to the surface. Detailed petrographical studies have been carried out with samples taken from surface rocks, cores, and cuttings from three wells (KHD-1, MTA-2, -3). X-ray diffraction techniques were also used in the present study. Kaolinite and montmorillonite zones were identified at outcrop samples. Chloritization, clay mineralization, sericitization and carbonization were determined in the ground mass of samples from wells. The observed alteration mineral assemblages indicate that K?z?lcahamam geothermal system has been cooling since the alteration minerals formed. The exploration well MTA-3 seems to be more suitable for a reinjection well than the other wells (MTA-2, -6), even if the cost of surface piping to transport the waste water to MTA-3 is higher than to another well (MTA-6).

Gevrek, A. I.

2000-03-01

275

Review of International Geothermal Activities and Assessment of US Industry Opportunites: Final Report  

SciTech Connect

This report contains detailed summaries, with bibliographies, of past, present, and planned geothermal development in 71 selected countries and areas. The report gives a pretty good description of types of work that had been done in each country by the mid 1980s, but does not tell much about which geothermal-provider country did the work. There are maps for most of the countries. There are numbers for market factors, but not for estimated geothermal potential. The information in this document has been superceded by the country summaries in the World Geothermal Congress Transactions of 1995, 2000, and 2005. This report was prepared by Meridian Corporation, Alexandria, VA. (DJE 2005)

None

1987-08-01

276

Recirculation System for Geothermal Energy Recovery in Sedimentary Formations: Laboratory Experiments and Numerical Simulations  

NASA Astrophysics Data System (ADS)

Geothermal energy resources are more widespread than previously thought and have the potential for providing a significant amount of sustainable clean energy worldwide. In particular, hot permeable sedimentary formations provide many advantages over traditional geothermal recovery and enhanced geothermal systems in low permeability crystalline formations. These include: (1) eliminating the need for hydraulic fracturing, (2) significant reduction in risk for induced seismicity, (3) reducing the need for surface wastewater disposal, (4) contributing to decreases in greenhouse gases, and (5) potential use for CO2 sequestration. Advances in horizontal drilling, completion, and production technology from the oil and gas industry can now be applied to unlock these geothermal resources. Here, we present experimental results from a laboratory scale circulation system and numerical simulations aimed at quantifying the heat transfer capacity of sedimentary rocks. Our experiments consist of fluid flow through a saturated and pressurized sedimentary disc of 23-cm diameter and 3.8-cm thickness heated along its circumference at a constant temperature. Injection and production ports are 7.6-cm apart in the center of the disc. We used DI de-aired water and mineral oil as working fluids and explored temperatures from 20 to 150 oC and flow rates from 2 to 30 ml/min. We performed experiments on sandstone samples (Castlegate and Kirby) with different porosity, permeability and thermal conductivity to evaluate the effect of hydraulic and thermal properties on the heat transfer capacity of sediments. The producing fluid temperature followed an exponential form with time scale transients between 15 and 45 min. Steady state outflow temperatures varied between 60% and 95% of the set boundary temperature, higher percentages were observed for lower temperatures and flow rates. We used the flow and heat transport simulator TOUGH2 to develop a numerical model of our laboratory setting. Given the remarkable match between our observations and numerical results, we extended our model to explore a wider range of thermal and hydrological parameters beyond the experimental conditions. Our results prove the capability of heat transfer in sedimentary formations for geothermal energy production.) Sandstone sample with two thermally insulating Teflon caps (white discs). In and out arrows indicate the flow direction while the sample is heated along its circumference (heater not shown). B) Example of a 2D temperature distribution during injection. White x shows the location of the flow ports, inlet (left) and outlet (right). Red is the set boundary temperature and blue is the fluid temperature at the inlet.

Elkhoury, J. E.; Detwiler, R. L.; Serajian, V.; Bruno, M. S.

2012-12-01

277

Geothermal Progress Monitor 12  

SciTech Connect

Some of the more interesting articles in this GPM are: DOE supporting research on problems at The Geysers; Long-term flow test of Hot Dry Rock system (at Fenton Hill, NM) to begin in Fiscal Year 1992; Significant milestones reached in prediction of behavior of injected fluids; Geopressured power generation experiment yields good results. A number of industry-oriented events and successes are reported, and in that regard it is noteworthy that this report comes near the end of the most active decade of geothermal power development in the U.S. There is a table of all operating U.S. geothermal power projects. The bibliography of research reports at the end of this GPM is useful. (DJE 2005)

None

1990-12-01

278

Hydrothermal alteration in the Reykjanes geothermal system: Insights from Iceland deep drilling program well RN-17  

NASA Astrophysics Data System (ADS)

The Reykjanes geothermal system is a seawater-recharged hydrothermal system that appears to be analogous to seafloor hydrothermal systems in terms of host rock type and low water/rock alteration. The similarities make the Reykjanes system a useful proxy for seafloor vents. At some time during the Pleistocene, the system was dominated by meteoric water recharge, and fluid composition at Reykjanes has evolved through time as a result of changing proportions of meteoric water influx as well as differing pressure and temperature conditions. The purpose of this study is to characterize secondary mineralization, degree of metasomatic alteration, and bulk composition of cuttings from well RN-17 from the Reykjanes geothermal system. The basaltic host rock includes hyaloclastite, breccia, tuff, extrusive basalt, diabase, as well as a marine sedimentary sequence. The progressive hydrothermal alteration sequence observed with increasing depth results from reaction of geothermal fluids with the basaltic host rock. An assemblage of greenschist facies alteration minerals, including actinolite, prehnite, epidote and garnet, occurs at depths as shallow as 350 m; these minerals are commonly found in Icelandic geothermal systems at temperatures above 250 °C (Bird and Spieler, 2004). This requires hydrostatic pressures that exceed the present-day depth to boiling point curve, and therefore must record alteration at higher fluid pressures, perhaps as a result of Pleistocene glaciation. Major, minor, and trace element profiles of the cuttings indicate transitional MORB to OIB composition with limited metasomatic shifts in easily mobilized elements. Changes in MgO, K 2O and loss on ignition indicate that metasomatism is strongly correlated with protolith properties. The textures of alteration minerals reveal alteration style to be strongly dependent on protolith as well. Hyaloclastites are intensely altered with calc-silicate alteration assemblages comprising calcic hydrothermal plagioclase, grandite garnet, prehnite, epidote, hydrothermal clinopyroxene, and titanite. In contrast, crystalline basalts and intrusive rocks display a range in alteration intensity from essentially unaltered to pervasive and nearly complete albitization of igneous feldspar and uralitization of clinopyroxene. Hydrothermal anorthite (An92-An98) occurs in veins in the most altered basalt cuttings and is significantly more calcic than igneous feldspar (An48-An79). Amphibole compositions change from actinolite to hornblende at depth. Hydrothermal clinopyroxene, which occurs in veins, has greater variation in Fe content and is systematically more calcic than igneous pyroxene and also lacks uralitic textures. Solid solutions of prehnite, epidote, and garnet indicate evolving equilibria with respect to aluminum and ferric iron.

Marks, Naomi; Schiffman, Peter; Zierenberg, Robert A.; Franzson, Hjalti; Fridleifsson, Gudmundur Ó.

2010-01-01

279

THERMAL CHARACTERISTICS OF THE CHENA HOT SPRINGS ALASKA GEOTHERMAL SYSTEM  

Microsoft Academic Search

Chena Hot Springs is located in the east-central part of the Alaska within the Yukon-Tanana Plateau, about 75 km east of Fairbanks. It is a moderate temperature deep circulation system typical of interior Alaska. The main shallow upflow zone is about 2000 ft long and 300 ft wide. The system is located at the edge of a granitic body where

Kamil Erkan; Gwen Holdman; David Blackwell; Walter Benoit

280

Application of seismic tomographic techniques in the investigation of geothermal systems  

SciTech Connect

The utility of microearthquake data for characterizing the Northwest Geysers geothermal field and the Long Valley Caldera (LVC) was investigated. Three-dimensional (3-D) P- and S-wave seismic velocity models were estimated for the Coldwater Creek Steam Field (CCSF) in the Northwest Geysers region. Hypocenters relocated using these 3-D models appear to be associated with the steam producing zone, with a deeper cluster of hypocenters beneath an active injection well. Spatial and temporal patterns of seismicity exhibit strong correlation with geothermal exploitation. A 3-D differential attenuation model was also developed for the CCSF from spectral ratios corrected for strong site effects. High-velocity anomalies and low attenuation in the near surface correspond to Franciscan metagraywacke and greenstone units. Microearthquakes recorded at seismographic stations located near the metagraywacke unit exhibit high corner frequencies. Low-velocity anomalies and higher attenuation in the near surface are associated with sections of Franciscan melange. Near-surface high attenuation and high Vp/Vs are interpreted to indicate liquid-saturated regions affected by meteoric recharge. High attenuation and low Vp/Vs marks the steam producing zone, suggesting undersaturation of the reservoir rocks. The extent of the high attenuation and low Vp/Vs anomalies suggest that the CCSF steam reservoir may extend northwestward beyond the known producing zone. This study concludes that microearthquake monitoring may be useful as an active reservoir management tool. Seismic velocity and attenuation structures as well as the distribution of microearthquake activity can be used to identify and delineate the geothermal reservoir, while temporal variations in these quantities would be useful in tracking changes during exploitation.

Romero, A.E. Jr.

1995-05-01

281

Microbiological monitoring in geothermal plants  

Microsoft Academic Search

In times of increasing relevance of alternative energy resources the utilization of geothermal energy and subsurface energy storage gains importance and arouses increasing interest of scientists. The research project ``AquiScreen'' investigates the operational reliability of geothermally used groundwater systems under microbial, geochemical, mineralogical and petrological aspects. Microbiological analyses based on fluid and solid phases of geothermal systems are conducted to

M. Alawi; S. Lerm; A. Vetter; A. Vieth; A. Seibt; M. Wolfgramm; H. Würdemann

2009-01-01

282

Geothermal drilling technology update  

SciTech Connect

Sandia National Laboratories conducts a comprehensive geothermal drilling research program for the US Department of Energy, Office of Geothermal Technologies. The program currently includes seven areas: lost circulation technology, hard-rock drill bit technology, high-temperature instrumentation, wireless data telemetry, slimhole drilling technology, Geothermal Drilling Organization (GDO) projects, and drilling systems studies. This paper describes the current status of the projects under way in each of these program areas.

Glowka, D.A.

1997-04-01

283

Fracture Propagation and Permeability Change under Poro-thermoelastic Loads & Silica Reactivity in Enhanced Geothermal Systems  

SciTech Connect

Geothermal energy is recovered by circulating water through heat exchange areas within a hot rock mass. Geothermal reservoir rock masses generally consist of igneous and metamorphic rocks that have low matrix permeability. Therefore, cracks and fractures play a significant role in extraction of geothermal energy by providing the major pathways for fluid flow and heat exchange. Therefore, knowledge of the conditions leading to formation of fractures and fracture networks is of paramount importance. Furthermore, in the absence of natural fractures or adequate connectivity, artificial fractures are created in the reservoir using hydraulic fracturing. Multiple fractures are preferred because of the large size necessary when using only a single fracture. Although the basic idea is rather simple, hydraulic fracturing is a complex process involving interactions of high pressure fluid injections with a stressed hot rock mass, mechanical interaction of induced fractures with existing natural fractures, and the spatial and temporal variations of in-situ stress. As a result, it is necessary to develop tools that can be used to study these interactions as an integral part of a comprehensive approach to geothermal reservoir development, particularly enhanced geothermal systems. In response to this need we have developed advanced poro-thermo-chemo-mechanical fracture models for rock fracture research in support of EGS design. The fracture propagation models are based on a regular displacement discontinuity formulation. The fracture propagation studies include modeling interaction of induced fractures. In addition to the fracture propagation studies, two-dimensional solution algorithms have been developed and used to estimate the impact of pro-thermo-chemical processes on fracture permeability and reservoir pressure. Fracture permeability variation is studied using a coupled thermo-chemical model with quartz reaction kinetics. The model is applied to study quartz precipitation/dissolution, as well as the variation in fracture aperture and pressure. Also, a three-dimensional model of injection/extraction has been developed to consider the impact poro- and thermoelastic stresses on fracture slip and injection pressure. These investigations shed light on the processes involved in the observed phenomenon of injection pressure variation (e.g., in Coso), and allow the assessment of the potential of thermal and chemical stimulation strategies.

Ahmad Ghassemi

2009-10-01

284

Comparing Maintenance Costs of Geothermal Heat Pump Systems with other HVAC Systems in Lincoln Public Schools: Repair, Service, and Corrective Actions.  

National Technical Information Service (NTIS)

The Lincoln Public School District, in Lincoln, Nebraska, recently installed vertical-bore geothermal heat pump systems in four, new, elementary schools. Because the district has consistent maintenance records and procedures, it was possible to study repa...

M. A. Martin D. J. Durfee P. J. Hughes

1999-01-01

285

The boron isotope systematics of Icelandic geothermal waters: 1. Meteoric water charged systems  

SciTech Connect

The authors have measured the boron isotope composition and boron and chloride concentrations of 27 Icelandic geothermal fluids from both high- and low-temperature systems. The {delta}{sup 11}B values range from {minus}6.7{per{underscore}thousand} in the Krafla system, to +25.0% in a warm spring from the Southern Lowlands. In addition, the authors have also determined the {delta}{sup 11}B values of basaltic glass from Nesjavellir ({minus}5.3 {+-} 1.4{per{underscore}thousand}) and travertine from Snaefellsnes ({minus}22 {+-} 0.5{per{underscore}thousand}). The B isotope and Cl/B systematics of the high-temperature systems are dominated by the composition of the local basalts. The lower temperature systems show evidence for mixing with B and Cl or a marine origin, together with some uptake of B into secondary mineral phases. The data from the Snaefellsnes geothermal system indicate that the fluids have undergone interaction with basalts that have undergone significant low-temperature alteration by seawater.

Aggarwal, J.K.; Palmer, M.R.; Bullen, T.D.; Arnorsson, S.; Ragnarsdottir, K.V.

2000-02-01

286

Measurement Requirements and Methods for Geothermal Reservoir System Parameters: An Appraisal.  

National Technical Information Service (NTIS)

One of the key needs in the advancement of geothermal energy is the availability of adequate measurements to aid the reservoir and production engineer in the development and operation of geothermal reservoirs, wells and the overall process plant. This rep...

M. D. Lamers

1979-01-01

287

System integration to produce concentrated brine and electricity from geopressured-geothermal reservoirs  

US Patent & Trademark Office Database

A systems design is disclosed which converts Geopressured-Geothermal (GPGT) brine into saturated brine in concert with the production of electricity from GPGT brine energy. The design integrates a GPGT conversion system which super-concentrates a portion of the GPGT brine, utilizing that portion's thermal energy, with a system designed to produce electricity from the remainder of GPGT brine energy. The end-brine from the electricity producing system is concentrated (sub-saturated) in a spray evaporation pond, which serves as a heat sink for both systems, and is combined with the super-saturated product brine from the GPGT conversion system, resulting in a saturated brine end-product. The saturated brine can be used for beneficial purposes, including for use as bulk material in the construction of salinity gradient solar ponds (SGSP), which collect, store, and deliver solar thermal baseload power (e.g., for electricity generation).

2014-04-29

288

Influence of time on metamorphism of sedimentary organic matter in liquid-dominated geothermal systems, western North America.  

USGS Publications Warehouse

Reflectance data of sedimentary organic matter samples from six liquid-dominated geothermal systems are strongly temperature-dependent. Geologic evidence indicates that reaction duration ranges from approx 103 to 106 yr in these systems that appear to have near-maximum temperatures. The strong temperature dependence of vitrinite reflectance indicates that after about 104 yr, reaction duration has little or no influence on metamorphism of organic matter in liquid-dominated geothermal systems. These data indicate that vitrinite reflectance can be used to determine the maximum temperature reached in hot sedimentary basins of moderate longevity. -after Author

Barker, C. E.

1983-01-01

289

District Heating with Geothermally Heated Culinary Water Supply Systems.  

National Technical Information Service (NTIS)

An initial feasibility study of using existing culinary water supply systems to provide hot water for space heating and air conditioning to a typical residential community is reported. The Phase I study has centered on methods of using low-to-moderate tem...

D. R. Pitts R. C. Schmitt

1979-01-01

290

Detecting and modeling subsurface fracture systems in geothermal fields using shear-wave splitting  

NASA Astrophysics Data System (ADS)

Shear wave splitting (SWS) is emerging as a useful exploration tool for geothermal fields as it can detect the geometry of the fracture system and the intensity of cracking within the geothermal reservoir. The method is based on the analyses of polarizations (?) and time delays (delta t) of split shear-waves that have been distorted by the anisotropy of the medium through which the seismic waves have propagated. Two experiments were conducted in Krafla and Hengill geothermal fields in Iceland in the summers of 2004 and 2005 respectively. Clear evidences of SWS were observed in both sites. In Krafla, in addition to the observed prevalence of a crack system oriented in approximately N--S direction which is consistent with the direction of regional rift zone, fast shear-wave polarization directions along a general E--W direction are also persistent. In Hengill, the measurements and consequent inversions of the shear-wave splitting parameters have provided evidence for a predominant fracture system oriented approximately NNE-SSW which is consistent with the regional tectonics in SW Iceland. Based on our previous research we have developed and consolidated a number of algorithms that can in principle make possible the automatic monitoring of subsurface fracture systems in geothermal fields. Seismic data are collected from an array of three-component seismic sensors. When a seismic event is detected it will be readily located provided that the record is available at no less than four seismometers. If shear-wave splitting is determined to be present for an event, both parameters (? and deltat) will be automatically measured using a newly developed method based on the analysis of multiple time windows. An automated SWS algorithm is performed for a series of time windows to yield a series of estimated pairs of ? and deltat, followed by a cluster analysis to finally determine the best estimate of polarization and time delay. Then, if the event is within the shear-wave window of any recording station, the measured parameters will be combined with all available measurements and used to invert for the orientation and intensity of cracks in the vicinity of that station.

Tang, Chuanhai

291

Using Estimated Risk to Develop Stimulation Strategies for Enhanced Geothermal Systems  

NASA Astrophysics Data System (ADS)

Enhanced geothermal systems (EGS) are an attractive source of low-carbon electricity and heating. Consequently, a number of tests of this technology have been made during the past couple of decades, and various projects are being planned or under development. EGS work by the injection of fluid into deep boreholes to increase permeability and hence allow the circulation and heating of fluid through a geothermal reservoir. Permeability is irreversibly increased by the generation of microseismicity through the shearing of pre-existing fractures or fault segments. One aspect of this technology that can cause public concern and consequently could limit the widespread adoption of EGS within populated areas is the risk of generating earthquakes that are sufficiently large to be felt (or even to cause building damage). Therefore, there is a need to balance stimulation and exploitation of the geothermal reservoir through fluid injection against the pressing requirement to keep the earthquake risk below an acceptable level. Current strategies to balance these potentially conflicting requirements rely on a traffic light system based on the observed magnitudes of the triggered earthquakes and the measured peak ground velocities from these events. In this article we propose an alternative system that uses the actual risk of generating felt (or damaging) earthquake ground motions at a site of interest (e.g. a nearby town) to control the injection rate. This risk is computed by combining characteristics of the observed seismicity of the previous 6 h with a (potentially site-specific) ground motion prediction equation to obtain a real-time seismic hazard curve; this is then convolved with the derivative of a (potentially site-specific) fragility curve. Based on the relation between computed risk and pre-defined acceptable risk thresholds, the injection is increased if the risk is below the amber level, decreased if the risk is between the amber and red levels, or stopped completely if the risk is above the red level. Based on simulations using a recently developed model of induced seismicity in geothermal systems, which is checked here using observations from the Basel EGS, in this article it is shown that the proposed procedure could lead to both acceptable levels of risk and increased permeability.

Douglas, John; Aochi, Hideo

2014-01-01

292

Temporary Bridging Agents for use in Drilling and Completion of Enhanced Geothermal Systems  

SciTech Connect

CSI Technologies, in conjunction with Alta Rock Energy and the University of Utah have undergone a study investigating materials and mechanisms with potential for use in Enhanced Geothermal Systems wells as temporary diverters or lost circulation materials. Studies were also conducted with regards to particle size distribution and sealing effectiveness using a lab-scale slot testing apparatus to simulate fractures. From the slot testing a numerical correlation was developed to determine the optimal PSD for a given fracture size. Field trials conducted using materials from this study were also successful.

Watters, Larry; Watters, Jeff; Sutton, Joy; Combs, Kyle; Bour, Daniel; Petty, Susan; Rose, Peter; Mella, Michael

2011-12-21

293

A review of progress in understanding the fluid geochemistry of the Cerro Prieto geothermal system  

USGS Publications Warehouse

Fluid geochemistry has played a major role in our present understanding of the Cerro Prieto geothermal system. Fluid chemical and isotopic compositions have been used to indicate the origin of water, salts and gases, original subsurface temperature and fluid flow, fluid-production mechanisms, and production-induced aquifer boiling and cold-water entry. The extensive geochemical data and interpretations for Cerro Prieto published from 1964 to 1981 are reviewed and discussed. Fluid geochemistry must continue to play an important role in the further development of the Cerro Prieto field. ?? 1984.

Truesdell, A. H.; Nehring, N. L.; Thompson, J. M.; Janik, C. J.; Coplen, T. B.

1984-01-01

294

Using estimated risk to develop stimulation strategies for induced seismicity in enhanced geothermal systems  

NASA Astrophysics Data System (ADS)

Enhanced Geothermal Systems (EGS) are an attractive source of low-carbon electricity and heating. Consequently, a number of tests of this technology have been made during the past couple of decades and various projects are being planned or under development. EGS work by the injection of fluid into deep boreholes to increase permeability and hence allow the circulation and heating of fluid through a geothermal reservoir. Permeability is irreversibly increased by the shearing of pre-existing factures or fault segments, and hence by the generation of microseismicity. One aspect of this technology that can cause public concern and consequently could limit the widespread adoption of EGS within populated areas is the risk of generating earthquakes that are sufficiently large to be felt (or even to cause building damage). Therefore, there is a need to balance stimulation and exploitation of the geothermal reservoir by injecting fluids against the pressing requirement to keep the earthquake risk below an acceptable level. Current strategies to balance these potentially conflicting requirements rely on a traffic light system based on the observed magnitudes of the triggered earthquakes and the measured peak ground velocities from these events. Douglas and Aochi (Pageoph, 2014) propose an alternative system that uses the actual risk of generating felt (or damaging) earthquake ground motions at a site of interest (e.g. a nearby town) to control the injection rate. This risk is computed by combining characteristics of the observed seismicity rate of the previous six hours, with a (potentially site-specific) ground-motion prediction equation to obtain a real-time seismic hazard curve, and then the convolution of this with the derivative of a (potentially site-specific) fragility curve. Based on the relation between computed risk and pre-defined acceptable risk thresholds the injection is: increased (if the risk is below the amber level), decreased (if the risk is between amber and red levels) or stopped completely (if the risk is above the red level). Based on simulations using a recently developed model of induced seismicity in geothermal systems (Aochi et al., GJI, 2014), which is validated here using observations from the Basel EGS in 2006, it is shown that the proposed procedure could lead to both acceptable levels of risk and increased permeability.

Douglas, John; Aochi, Hideo

2014-05-01

295

South Dakota geothermal resources  

SciTech Connect

South Dakota is normally not thought of as a geothermal state. However, geothermal direct use is probably one of the best kept secrets outside the state. At present there are two geothermal district heating systems in place and operating successfully, a resort community using the water in a large swimming pool, a hospital being supplied with part of its heat, numerous geothermal heat pumps, and many individual uses by ranchers, especially in the winter months for heating residences, barns and other outbuildings, and for stock watering.

Lund, J.W.

1997-12-01

296

Design and Implementation of Geothermal Energy Systems at West Chester University  

SciTech Connect

West Chester University is launching a comprehensive transformation of its campus heating and cooling systems from traditional fossil fuels (coal, oil and natural gas) to geothermal. This change will significantly decrease the institution's carbon footprint and serve as a national model for green campus efforts. The institution is in the process of designing and implementing this project to build well fields, a pumping station and install connecting piping to provide the geothermal heat/cooling source for campus buildings. This project addresses the US Department of Energy Office of Energy Efficiency and Renewable Energy (EERE) goal to invest in clean energy technologies that strengthen the economy, protect the environment, and reduce dependence on foreign oil. In addition, this project advances EERE's efforts to establish geothermal energy as an economically competitive contributor to the US energy supply. For this grant, WCU will extend piping for its geo-exchange system. The work involves excavation of a trench approximately 8 feet wide and 10-12 feet deep located about 30 feet north of the curb along the north side of West Rosedale for a distance of approximately 1,300 feet. The trench will then turn north for the remaining distance (60 feet) to connect into the mechanical room in the basement of the Francis Harvey Green Library. This project will include crossing South Church Street near its intersection with West Rosedale, which will involve coordination with the Borough of West Chester. After installation of the piping, the trench will be backfilled and the surface restored to grass as it is now. Because the trench will run along a heavily-used portion of the campus, it will be accomplished in sections to minimize disruption to the campus as much as possible.

Greg Cuprak

2011-08-31

297

Geothermal Water Use: Life Cycle Water Consumption, Water Resource Assessment, and Water Policy Framework  

DOE Data Explorer

This report examines life cycle water consumption for various geothermal technologies to better understand factors that affect water consumption across the life cycle (e.g., power plant cooling, belowground fluid losses) and to assess the potential water challenges that future geothermal power generation projects may face. Previous reports in this series quantified the life cycle freshwater requirements of geothermal power-generating systems, explored operational and environmental concerns related to the geochemical composition of geothermal fluids, and assessed future water demand by geothermal power plants according to growth projections for the industry. This report seeks to extend those analyses by including EGS flash, both as part of the life cycle analysis and water resource assessment. A regional water resource assessment based upon the life cycle results is also presented. Finally, the legal framework of water with respect to geothermal resources in the states with active geothermal development is also analyzed.

Jenna N. Schroeder

298

Direct utilization of geothermal heat in cascade application to aquaculture and greenhouse systems at Navarro College. Annual report, January-December 1983  

Microsoft Academic Search

Progress is reported on a project for the use of the 130°F central Texas geothermal resource. The milestones in the construction of the system for cascading the geothermal enenrgy through two enclosed aquaculture ponds, a greenhouse heating system, and a collection catfish reservoir are reported. (MHR)

1983-01-01

299

Direct Utilization of Geothermal Heat in Cascade Application to Aquaculture and Greenhouse Systems at Navarro College. Annual Report, January 1984-September 1984.  

National Technical Information Service (NTIS)

Progress is reported on a project to use the 130 exp 0 F geothermal resource in central Texas. The system for cascading geothermal energy through aquaculture and greenhouse systems was completed and the first shrimp harvest was held. (ERA citation 10:0004...

K. Smith

1984-01-01

300

Direct Utilization of Geothermal Heat in Cascade Application to Aquaculture and Greenhouse Systems at Navarro College. Annual Report, January-December 1983.  

National Technical Information Service (NTIS)

Progress is reported on a project for the use of the 130 exp 0 F central Texas geothermal resource. The milestones in the construction of the system for cascading the geothermal enenrgy through two enclosed aquaculture ponds, a greenhouse heating system, ...

K. Smith

1983-01-01

301

Direct utilization of geothermal heat in cascade application to aquaculture and greenhouse systems at Navarro College. Annual report, January-December 1983  

SciTech Connect

Progress is reported on a project for the use of the 130/sup 0/F central Texas geothermal resource. The milestones in the construction of the system for cascading the geothermal enenrgy through two enclosed aquaculture ponds, a greenhouse heating system, and a collection catfish reservoir are reported. (MHR)

Smith, K.

1983-12-30

302

Monitoring of Building Heating and Cooling Systems Based on Geothermal Heat Pump in Galicia (Spain)  

NASA Astrophysics Data System (ADS)

In November 2009 was signed an agreement between Galicia's Government and EnergyLab to develop a project related with the geothermal heatpumps (hereafter, GSHP) technology. That project consisted in replacing the existing thermal equipment generators (diesel boilers and air-water heat pumps) by GSHP systems in representative public buildings: two nursery schools, a university library, a health centre and a residential building. This new systems will reach the demands of existing heating, cooling and domestic hot water (hereafter, DHW). These buildings can serve as examples of energy and economic savings that can offer this technology. We will show detailed analysis of the GSHP facilities monitored, since the starting-up of them. Which includes: COP's, EER's, energy consumption, operating costs, operation hours of the system, economic and emissions comparative, geothermal exchange evolution graphs, environmental conditions evolution graphs (temperature and demands), etc. The results presented show an example of the important benefits of the GSHP technology and the significant savings that can offer its implementation for heating, cooling and DHW production. Note to the reader: The article number has been corrected on web pages on November 22, 2013.

Iglesias, M.; Rodriguez, J.; Franco, D.

2012-10-01

303

Numerical simulations to assess thermal potential at Tauranga low-temperature geothermal system, New Zealand  

NASA Astrophysics Data System (ADS)

Tauranga low-temperature geothermal system (New Zealand) has been used for the last 40 years for direct uses including space heating, bathing and greenhouses. Warm-water springs in the area are between 22 and 39 °C, with well temperatures up to 67 °C at 750 m depth. A heat and fluid flow model of the system is used to determine reservoir properties and assess thermal potential. The model covers 130 km by 70 km to 2 km depth, and was calibrated against temperatures measured in 17 wells. Modelling shows that to maintain the observed primarily conductive heat flow regime, bulk permeability is ?2.5 × 10-14 m2 in sedimentary cover and ?1 × 10-16 m2 in the underlying volcanic rocks. The preferred model (R 2 = 0.9) corresponds to thermal conductivities of 1.25 and 1.8 W/m2 for sedimentary and volcanic rocks, respectively, and maximum heat flux of 350 mW/m2. The total surface heat flow is 258 MW over 2,200 km2. Heat flux is highest under Tauranga City, which may be related to inferred geology. Model simulations give insights into rock properties and the dynamics of heat flow in this low-temperature geothermal system, and provide a basis to estimate the effects of extracting hot fluid.

Pearson, S. C. P.; Alcaraz, S. A.; Barber, J.

2013-12-01

304

The Iceland Deep Drilling Project (IDDP): (7) Arsenic distribution within a Basalt-Hosted, High-Temperature Geothermal System, Reykjanes, Iceland  

NASA Astrophysics Data System (ADS)

The Reykjanes geothermal system is an active, high-temperature, seawater-dominated system located on the southwestern coast of Iceland and is a target site for deep drilling by the Iceland Deep Drilling Project (IDDP). Geothermal fluids produced from drillholes in the Reykjanes geothermal system contain As concentrations up to 240 ppb; however, the distribution of arsenic within the geothermal system is poorly known. The Reykjanes geothermal system is located along the landward continuation of the Mid-Atlantic Ridge (MAR) and has been studied extensively through the efforts of the IDDP and others, and so provides an opportunity to evaluate the hydrothermal geochemistry of arsenic in a basalt-hosted geothermal system. We measured the bulk rock concentration of As, Fe, S, Ti and thirteen other trace metals and metalloids by ICP-MS and ICP-OES in fifty drillhole cutting samples from 350 to 3050 m depth in Reykjanes geothermal well RN-17. The host rock consists of layers of hyaloclastite and fractured crystalline basalts that are frequently intruded by shallow mafic intrusives. Previous studies indicate that the As content of Icelandic basalts is related to their degree of differentiation, with olivine-tholeiites containing 0.02-0.18 ppm As, tholeiites 0.36-0.38 ppm As, and Icelandites 0.76-1.59 ppm As. In RN-17, As content varied between 0.4 and 0.8 ppm for ~70% of the 2700 m profile, suggesting a background concentration of ~0.6 ppm As for the system. The As minima was 0.3 ppm at 2000 m. There were two distinct As maxima in the drillhole cuttings: As was elevated to 0.8-2.3 ppm and 1.7-2.9 ppm at 400-650 m and 1750-1900 m, respectively. From 2300 to ~2700 m, arsenic was slightly elevated (>0.6 - 1.1 ppm). Of the elements analyzed, As correlated most closely with S, and it did so more closely than any of the other elements, including the common chalcophiles Ni, Cu, Zn and Pb. This suggests that hydrothermal sulfides efficiently sequester arsenic and that arsenic is behaving similarly to sulfur within high-temperature geothermal systems. The depths at which arsenic and sulfur were enriched partially overlap with hyaloclastite basaltic tuffs and/or breccias, suggesting that host-rock permeability and the related variables of fluid pressure and water/rock ratio may control sulfide formation and therefore also arsenic distribution. Within the global As cycle, As is concentrated in sedimentary rocks (5-10 ppm) and in felsic extrusive rocks (3.2-5.4 ppm). The results presented here indicate that hydrothermal alteration of basaltic rocks also locally concentrates As up to ~ 3 ppm, producing initial As and S heterogeneities that will influence the geochemical signature of later metamorphism.

Olsen, N. J.; Bird, D. K.; Arnórsson, S.; Fridriksson, T.; Fridleifsson, G. O.; Elders, W. A.

2009-12-01

305

Volcanology and geothermal energy  

SciTech Connect

The aim of this book is to demonstrate how volcanological concepts can be applied to the evaluation and exploration of geothermal energy resources. In regard to the geothermal content of the book, some of the information comes from the first-hand experience gained during the authors' exploration work in Middle America and with the Los Alamos Hot Dry Rock program. Other cases discussed come from classic geothermal systems in many regions and settings. The book begins with a summary of recent practical advances in volcanology, and then moves on to describe the considerable importance of pyroclastic rocks as a took to evaluate geothermal systems, including an in-depth treatment of hydrovolcanism. Following chapters deal with surface manifestations of geothermal systems, and systems associated with calderas, silicic lava domes, and basaltic volcanoes. The last chapter is on geothermal systems in maturing composite volcanoes. The Appendices include a broad overview of field methods in volcanic regions, volcanic rock classifications and properties, thermodynamic properties of water vapor (steam tables), and the use of cuttings in geothermal well logs. A two-dimensional heat flow code used for estimating geothermal resources is also given. The book makes two significant contributions: first, in its treatment of eruption dynamics, focusing on quantitative and theoretical analysis of volcanic processes, and second, in its comprehensive treatment of the fundamentals of hydrovolcanism, including fuel-coolant interactions and hydrofracturing.

Wohletz, K.; Heiken, G.

1992-01-01

306

Numerical simulations of heat transfer through fractured rock for an enhanced geothermal system development in Seokmodo, Korea  

NASA Astrophysics Data System (ADS)

Estimating the expected capacity and efficiency of energy is a crucial issue in the construction of geothermal plant. It is the lasting temperature of extracted geothermal water that determines the effectiveness of enhanced geothermal systems (EGS), so the heat transfer processes in geothermal reservoirs under site-specific geologic conditions should be understood first. The construction of the first geothermal plant in Korea is under planning in Seokmodo, where a few flowing artesian wells showing relatively high water temperature of around 70°C were discovered lately. The site of interest is a part of the island region, consisting of the reclaimed land surrounded by the sea and small mountains. Geothermal gradient measures approximately 45°C/km and the geothermal water is as saline as seawater. Geologic structure in this region is characterized by the fractured granite. In this study, thermo-hydrological (TH) numerical simulations for the temperature evolution in a fractured geothermal reservoir under the supposed injection-extraction operating conditions were carried out using TOUGH2. Multiple porosity model which is useful to calculate the transient interporosity flow in TH coupled heat transfer problem was used in simulations. Several fracture planes which had been investigated in the field were assigned to have highly permeable properties in order to avoid the averaging approximation and describe the dominant flow through the fractures. This heterogeneous model showed the rise of relatively hot geothermal water in the densely fractured region. The temperature of the extracted geothermal water also increased slowly for 50 years due to the rising flow through the fractures. The most sensitive factor which affects the underground thermal distribution and temperature of geothermal water was permeability of the medium. Change in permeabilities of rock and fracture within the range of 1 order might cause such an extreme change in the temperature of geothermal water that the measurement of the permeability should be performed through a very careful process in order to guarantee a reliable simulation. As the fracture spacing became narrower, overall thermal distribution appeared to be similar to that from EPM model. This suggests that EPM model, which is easy to design and takes less time, can be replaced for the densely fractured medium. Change in fracture aperture within the range of that of actual rocks did not cause a remarkable difference in temperature distribution, which means that measuring accuracy of the actual aperture value in rocks is relatively less important. This demonstrates that the distribution and the structure of fracture system make a great contribution to the whole simulation for fluid and heat flow mechanisms in geologic medium, and thus require an intensive geologic investigation for the fractures including strike and dip information, permeability and connecting relation. In addition, the simulation results show that the heterogeneous model can include the description for the significant fracture flow and it can be a practical tool for a site-specific simulation for EGS sites. This preliminary simulation was useful to estimate the scale of the geothermal reservoir and the energy potential in Seokmodo and it can be further expanded to a long-term simulation to predict the evolution of the geothermal reservoir under the potential EGS operations. Acknowledgement: This study was financially supported by KIGAM, KETEP and BK21.

Shin, Jiyoun; Kim, Kyung-Ho; Hyun, Yunjung; Lee, Kang-Keun

2010-05-01

307

Stragegies to Detect Hidden Geothermal Systems Based on Monitoringand Analysis of CO2 in the Near-Surface Environment  

SciTech Connect

We investigate the potential for CO2 monitoring in thenear-surface environment as an approach to exploration for hiddengeothermal systems. Numerical simulations of CO2 migration from a modelhidden geothermal system show that CO2 concentrations can reach highlevels in the shallow subsurface even for relatively low CO2 fluxes.Therefore, subsurface measurements offer an advantage over above-groundmeasurements which are affected by winds that rapidly disperse CO2. Tomeet the challenge of detecting geothermal CO2 emissions within thenatural background variability of CO2, we propose an approach thatintegrates available detection and monitoring techniques with statisticalanalysis and modeling.

Lewicki, Jennifer L.; Oldenburg, Curtis M.

2005-03-29

308

Geothermal Systems In The Snake River Plain Idaho Characterized By The Hotspot Project  

NASA Astrophysics Data System (ADS)

The Snake River Plain (SRP) is potentially the largest geothermal province in the world. It is postulated that the SRP results from passage of the North American Plate over the Yellowstone mantle plume. This has resulted in felsic, caldera-related volcanism followed by voluminous eruptions of basalt. Compilations of subsurface temperature data demonstrate the masking effect of the Snake River Aquifer. As a consequence, here has been little serious geothermal exploration within the center of the plain; although there are numerous examples of low-temperature fluids, as well as the Raft River geothermal system, on the southern flanks of the SRP. Project Hotspot was designed to investigate the geothermal potential of the SRP through the coring and subsequent scientific evaluation of three holes, each representing a different geothermal environment. These are located at Kimama, north of Burley, in the center of the plain; at Kimberly near Twin Falls on the southern margin of the plain; and at Mountain Home Air Force base in the central part of the western SRP. Both the Kimberly and Mountain Home sites are located in areas that have warm wells and hot springs, whereas, the Kimama site has neither surface nor subsurface thermal manifestations. All of the sites studied here were sampled using slim hole coring techniques in conjunction with a bottom hole temperature probe developed by DOSECC. Our first hole at Kimama in the center of the eastern SRP was cored to a depth of 1,912 m. Temperature measurements showed the SRP fresh water aquifer extends to a depth of 965 m and masks the underlying high temperature gradient of 74.5oC/Km. The core hole at Kimberly reached a depth of 1,959 m and demonstrated a large low-temperature resource of >50oC below 800 m. A core hole at Mountain Home AFB in the eastern SRP reached a depth of 1,821 m and demonstrated the presence of an intermediate- to high-temperature artesian resource that has a clear magmatic association, with measured temperatures of up to 140oC and extrapolated equilibrium temperatures of 150oC. Calculated equilibrium temperatures of the artesian water samples vary from ~134oC to 154oC (Lachmar et al 2012; GRC Transactions). The Kimama hole greatly expanded the depth extent of the Snake River aquifer. However, beneath the masking effect of the aquifer, high temperature gradients were encountered suggesting that high-temperature resources could be present, but their identification could be difficult. The Kimberly hole demonstrated that low-temperature resources along the southern flank of the SRP can have considerable depth extent and are higher volume than previously anticipated. The overall architecture of this large low-temperature system deserves further investigation. Hole MH-2 Mountain Home AFB in the central part of the western SRP has encountered the upper part of a high temperature geothermal resource that also remains to be fully evaluated.

Nielson, D. L.; Delahunty, C.; Shervais, J. W.

2012-12-01

309

Evidence for a Magmatic Source of Heat for the Steamboat Springs Geothermal System Using Trace Elements and Gas Geochemistry  

Microsoft Academic Search

The objective of this project is the development of a representa- tive geochemical database for a comprehensive suite of elemental and isotopic parameters (i.e., beyond the typical data suite) for geo- thermal fluids in the Great Basin. Preliminary assessment suggests that there are significant differences between magmatic-driven and extensional geothermal systems. In particular, fluids in magmatic systems have higher concentrations

Greg B. Arehart; Mark F. Coolbaugh; Simon R. Poulson

310

Geothermal direct-heat utilization assistance  

NASA Astrophysics Data System (ADS)

The report summarizes activities of the Geo-Heat Center (GHC) at Oregon Institute of Technology for the first quarter of Fiscal Year 1995. It describes contacts with parties during this period related to assistance with geothermal direct heat projects. Areas dealt with include geothermal heat pumps, space heating, greenhouses, aquaculture, resources and equipment. Research is also being conducted on geothermal energy cost evaluation, low-temperature geothermal resource assessment, use of silica waste from the Cerro Prieto geothermal field as construction materials and geothermal heat pumps. Outreach activities include the publication of a quarterly bulletin on direct heat applications and dissemination of information on low-temperature geothermal resources and utilization.

311

Summary of geothermal exploration activity in the state of Washington from 1978 to 1983  

SciTech Connect

During the course of conducting the statewide reconnaissance study of Washington's potential geothermal resources, several specific areas and broader regions have been identified as targets which warrant a more concentrated effort. Over the past three years, the program has continued to identify new sites, but has concentrated on better defining the resource potential of the best areas. The locations of these geothermal areas are shown, and the level of progress for each area is shown, expressed as a percentage of completion for the various exploration tasks. Descriptions of the geothermal target areas are presented.

Korosec, M.A.

1984-01-01

312

Imperial County geothermal development. Quarterly report, April 1-June 30, 1982  

SciTech Connect

The activities of the Geothermal Office during the quarter are discussed, including: important geothermal events, geothermal waste disposal, a grant award by the California Energy Commission, the geothermal development meeting, and the current status of geothermal development in Imperial County. Activities of the Geothermal Planner are addressed, including permits, processing of EIR's, and other planning activities. Progress on the direct heat study is reported.

Not Available

1982-06-30

313

Isotopic evidence for magmatic and meteoric water recharge and the processes affecting reservoir fluids in the Palinpinon geothermal system, Philippines  

SciTech Connect

Stable isotopic compositions of meteoric and geothermal waters indicate that the Palinpinon geothermal system of Southern Negros is fed by a parent water that originated from a mixture of local meteoric (80%) and magmatic (20%) waters. The meteoric water has an isotopic concentration of {minus}8.5{per_thousand} and {minus}54{per_thousand} in {sup 18}O and {sup 2}H, respectively, which corresponds to an average infiltration altitude of about 1,000 m above sea level. With exploitation of the system and injection of wastewaters to the reservoir, the stable isotopic composition became heavier due to significant mixing of geothermal fluids with injection waters. Incursion of cooler meteoric waters, which is confirmed by the presence of tritium, also leads to the formation of acid-sulfate waters. Stable isotopes are effective as ``natural tracers`` to determine the origin and mixing of different fluids in the reservoir.

Gerardo, J.Y.; Seastres, J.S. Jr. [Philippine National Oil Co.-Energy Development Corp., Fort Bonifacio (Philippines). Geothermal Div.] [Philippine National Oil Co.-Energy Development Corp., Fort Bonifacio (Philippines). Geothermal Div.; Nuti, S.; D`Amore, F. [Ist. Internazionale per le Ricerche Geotermiche, Pisa (Italy)] [Ist. Internazionale per le Ricerche Geotermiche, Pisa (Italy); Gonfiantini, R. [International Atomic Energy Agency, Vienna (American Samoa). Isotope Hydrology] [International Atomic Energy Agency, Vienna (American Samoa). Isotope Hydrology

1993-10-01

314

Reconstructing the geological and structural history of an active geothermal field: A case study from New Zealand  

NASA Astrophysics Data System (ADS)

The utilisation of geothermal systems benefits from an understanding of the host-rock geology, locations and controls of permeability pathways, and the nature and timing of magmatic sources providing thermal energy. Kawerau Geothermal Field in the central Taupo Volcanic Zone (TVZ) of New Zealand is currently developed for electricity generation and direct uses of high-temperature steam to ~ 200 MW electrical output. The Kawerau geothermal system is hosted in a sequence of volcanic lithologies (tuffs, lavas and intrusive bodies) and sediments that overlie faulted Mesozoic metasedimentary (greywacke) basement. Identification of lithologies in the volcanic/sedimentary sequence is challenging due to the levels of hydrothermal alteration and lithological similarities. A combination of detailed petrological investigations, consideration of the emplacement processes and greater certainty of crystallisation or eruption ages through U-Pb age determinations on zircons is used to reconstruct the depositional and faulting evolution of the rocks hosting the currently active hydrothermal system. The oldest event inferred is faulting of the greywacke along northwest-southeast orientated, dominantly strike-slip structures to generate half-grabens that were filled with sediments, incorporating two dated ignimbrites (2.38 ± 0.05 and 2.17 ± 0.05 Ma). A 1.46 ± 0.01 Ma ignimbrite was deposited relatively evenly across the field, implying that any topographic relief was subdued at that time. Subsequent deposition of ignimbrites occurred in episodes around 1.0, 0.55-0.6, and 0.32 Ma, interspersed with thin sedimentary sequences that accumulated at average rates of 0.06 mm yr- 1. Andesite lavas from a buried composite cone occur as a conformable package between units dated at 1.0 and 0.6 Ma. Bodies of coherent rhyolite occur at multiple stratigraphic levels: two magma types with associated tuffs were emplaced as domes and sills at 0.36 ± 0.03 Ma, and a third type at 0.138 ± 0.007 Ma as dikes, and domes that are exposed at surface. The andesitic Putauaki composite cone southwest of the field first erupted around 8 ka, but earlier hydrothermal eruption breccias imply that magma was intruded to shallow depths as early as ~ 16 ka. Age data and associated correlations show that post-1.5 Ma normal faulting has accompanied episodic subsidence of the Kawerau area, with fault movement focused between northeast-southwest structures (associated with the geometry of the modern TVZ) and the reactivated northwest-southeast structures associated with most displacement in the area prior to 1.5 Ma. Contrasts between emplacement of coherent rhyolite as sills at 0.36 Ma and a dike at 0.138 Ma reflect a shift in orientation of the principal stress axes in response to initiation of the modern TVZ rifting regime. Most volcanic rocks at Kawerau are distally sourced from elsewhere in the TVZ but form local marker horizons that delineate topographic relief within the field, and additionally constrain past subsidence rates. Current rates of subsidence and thermal output at Kawerau are geologically recent features associated with latest Quaternary rifting processes (< ~ 50 ka) and emplacement of the magmatic system for Putauaki volcano (~ 16 ka) respectively.

Milicich, S. D.; Wilson, C. J. N.; Bignall, G.; Pezaro, B.; Bardsley, C.

2013-07-01

315

Enhanced Geothermal Systems (EGS) - Where Are We Now  

NASA Astrophysics Data System (ADS)

There were seven major EGS projects in which reservoir circulation was achieved prior to the Geodynamics Limited project in the Innamincka granite in northern South Australia which commenced in 2002. Six other projects did not achieve significant circulation. Importantly all but one of these projects were located in granitic bodies in which it is assumed that families of existing natural fractures are present. Evidence from all these EGS projects indicated that: 1 Stimulation in granite rock resulting from water injection with no added chemicals enhanced rock fracture permeability by 2-3 orders of magnitude. 2 The increased permeability resulted from increased fracture porosity associated with slippage on existing natural fractures during the stimulation. 3The extent of the resulting reservoir could be accurately mapped by acoustic (micro-seismic) monitoring of the fracture slippages. 4 The orientation of the reservoir is strongly dependent on the relative directions of the three principle rock stress axes. 5 The stimulation pumping pressures required were 50-75% of the minimum principle stress for the depth of reservoir creation in accord with geomechanical theory, and are therefore lower than those required to open tensile fractures (fracking). 6 The size of the resulting stimulated reservoir is proportional to the volume of water injected. New space created by the increase in fracture porosity associated with the micro-seismic events is taken up by the injected water. 7 Most projects to 2002 were carried out in strike-slip and normal faulting stress regimes with minimum stress direction horizontal and the resulting reservoirs were oriented close to vertically. 8 Volcanic activity can only occur in strike-slip and normal faulting stress regimes so EGS reservoirs in volcanic areas will be oriented close to vertically. 9 The Fjallbacka project in Sweden was the only project carried out in an overthrust stress regime (minimum stress direction vertical) and the reservoir was oriented horizontally. It is with these understandings that the Geodynamics field program commenced near Innamincka in 2002 where high temperature granite basement had been intersected at 3.6 km depth by petroleum exploration wells. Gravity and heat flow models indicated the basement granite to be 10 km thick and that most of the heat flow (> 100 mW/m2) was derived from elevated thorium and uranium levels in the granite. The stress environment was thought to be overthrust, but this was not certain.The results of the Geodynamics field program consists of drilling 5 wells to the granite, stimulation in three of those wells, flow testing in two of those wells and circulation between two of those wells. There are now four main barriers to economic deployment of EGS throughout the world for electricity generation. One is the cost of drilling and new technologies need to be developed to increase drilling ROP in high strength rocks. The other three relate to reservoir development and increased flow rate. These are (i) new geophysical tools to locate large fractures remotely (ii) deployment of temporary fracture sealing agents to allow enhancement in more than one fracture, and (iii) decreased flow impedance in a given fracture at the production well. New projects at different locations around the world are required to test ways of overcoming these barriers.

Wyborn, D.

2011-12-01

316

Microbial and Chemical Characterization of Geothermal Ground Water  

NASA Astrophysics Data System (ADS)

Subsurface geothermal sites are commonly colonized by chemolithotrophic bacteria which use rock minerals and CO_2 as sole nutrients. This type of ``life cradle'' may not only be common on Earth but may also be a likely scenario on many other planets. Three geothermal sites in southern New Mexico have been chosen to characterize geothermal waters for microbial diversity and chemical content. All sites of this on-going study are located on or near the Rio Grande Rift and are tapped into fractured reservoir systems of Paleozoic carbonate rocks, Tertiary volcanic rocks or consolidated basin-fill sediments. Geothermal fluids were analyzed for major cations and anions, selected trace elements, TOC, phosphate, fluoride and dissolved gases. The microbial analysis included phospholipid fatty acid (PLFA) analysis and DNA sequencing. Geothermal ground water was high in dissolved solids, had high concentrations of carbon dioxide and was more acidic than adjacent ground water not affected by geothermal activity. Geothermal ground-water samples contained very low amounts of biomass composed of relatively simple microbial communities. Several species of Archaebacteria were detected in some of the ground water that was derived from wells tapping into deep fractured systems. The analysis of denaturing gradient gel electrophoresis (DGGE) images indicated distinct differences of the types of microbes present in geothermal water compared to an adjacent deep non-thermal flow system.

Schulze-Makuch, Dirk; Kennedy, John

317

Geochemistry and the Exploration of the Ngawha Geothermal System, New Zealand  

SciTech Connect

The Ngawha geothermal system is atypical of New Zealand geothermal systems, being located outside the Taupo Volcanic Zone, and contained in tight sedimentary structures. Early geochemical surveys of surface discharges indicated a high gas, high borate fluid, discharging in small quantities, to the surface. An initial well (drilled in the early 1960’s, to 500m) produced a vary gassy fluid before calciting. Deeper wells drilled and discharged in the early 1980’s produced large flows of high gas fluid (up to 3wt%), at enthalpies around 1000 kj/kg. These low energy contents coupled with a low water to rock ratio, a very fractured structure, and consequent expected changes in the production fluid following exploitation, let do large scale exploitation plans being scrapped in 1982. The close attention to geochemical studies before and during the drilling operations enabled predictions of fluid type, physical conditions at depth, fluid disposal problems, and hydrologic reservoir models that have proved to be correct. The project served to indicate the value of comprehensive exploration strategies which precede the drilling phase, and the further value of, in particular, geochemical studies as an integral part of well testing procedures, for the updating of reservoir models. The close and open cooperation amongst the scientist and engineers involved was also of great value. 2 tabs., 4 figs., 15 refs.

Sheppard, D.S.

1987-01-20

318

Volcanology and geothermal energy  

Microsoft Academic Search

The authors of Volcanology and Geothermal Energy both integrate and link such fast growing and extensive topics as volcanology, geochemistry, reservoir engineering, and applied geophysics. Topics of particular interest presented in this book include the following: Hydrovolcanism; hydrofracture; principles of ore geology; Calderas and their geothermal systems. Important appendices are included.

K. Wohletz; G. Heiken

1992-01-01

319

Characterization of medium enthalpy geothermal system in the Campania region (southern Italy): from geological data to resource modelling  

NASA Astrophysics Data System (ADS)

Within the framework of the VIGOR project, a characterization of medium enthalpy geothermal resources have been carried out in the Campania region (southern Italy), with a focus on the "Guardia dei Lombardi" area (province of Avellino). The VIGOR project began on the basis of an agreement between the Ministry of Economic Development and the Italian National Research Council, and it deal with the exploitation of innovative uses of geothermal energy in the so-called "regions of convergence"(Campania, Calabria, Puglia and Sicilia). Thanks to the intense hydrocarbon exploration, carried out particularly during the 1956-1996 period, an extensive data set made up by deep wells and seismic reflection profiles exist in the study area. The previous exploration demonstrated the presence of a fractured carbonate reservoir, mainly belonging to the Cretaceous section of the Apulian shallow water carbonate platform (e.g. Scrocca 2010 and references therein), which is deformed to shape a buried antiformal stack. The culmination of the uppermost thrust unit reaches a depth of about 200 m SSL (i.e., about 1100 m below the ground level). The reservoir fluids are made up by a CO2 gas cap, which rests above an accumulation of fresh water in the central and upper part of the culmination of the deep carbonatic acquifer (e.g., Monte Forcuso 1 and 2 wells), and a saline water along the flank of the buried anticline (e.g., Bonito 1 Dir, Ciccone 1 wells). Medium enthalpy geothermal resources with a reservoir fluid temperature up to 100°C have been estimated in previous assessments at depth of 2000 m below ground level (ENEL 1987; 1994). However, the presence of thermal springs (e.g. Terme di S. Teodoro) in the area suggests the presence of an active hydraulic circuit and provide further constraints about the geochemical characteristics of the reservoir waters, and the geothermometers investigation (Duchi et al. 1995) give a possible reservoir fluid temperature up to about 124 °C. In this study, the overall reservoir/caprock system structural-stratigraphic setting has been defined based on the integrated interpretation of surface geology, public and available seismic reflection profiles, and composite well logs. In particular, a careful assessment of temperature field at depth has been carried out analyzing the well logs through Horner plot construction (Rider, 1996 and reference therein). Where the temperature data data were scarce or poorly constrained, the approach proposed by Della Vedova, et al. (2001) has been applied. On the basis of well tests, cores and mud losses/absorptions, the reservoir permeability was also re-estimated, confirming quite good permeability values for the fractured carbonate reservoir. One of the main results of this research is the development of an integrated 3D geological model which provides the base for a detailed assessment of the possible geothermal exploitation of the carbonate reservoir. The preliminary results of our analysis suggest that "Guardia dei Lombardi" can be indicated as an interesting area for the geothermal medium enthalpy exploitation, although the presence of the CO2 gas cap and the scaling capability of the deep fluids should be carefully evaluated. From the 3D geological model, we put a sounding basis for a numerical model of hot fluid extraction (made by TOUGH/TOUGHREACT) in which some reasonable hypothesis on the reservoir exploitation may be evaluated.

Montegrossi, G.; Inversi, B.; Scrocca, D.; Livani, M.; Petracchini, L.

2012-04-01

320

Geothermal Program Review XI: proceedings. Geothermal Energy - The Environmental Responsible Energy Technology for the Nineties  

SciTech Connect

These proceedings contain papers pertaining to current research and development of geothermal energy in the USA. The seven sections of the document are: Overview, The Geysers, Exploration and Reservoir Characterization, Drilling, Energy Conversion, Advanced Systems, and Potpourri. The Overview presents current DOE energy policy and industry perspectives. Reservoir studies, injection, and seismic monitoring are reported for the geysers geothermal field. Aspects of geology, geochemistry and models of geothermal exploration are described. The Drilling section contains information on lost circulation, memory logging tools, and slim-hole drilling. Topics considered in energy conversion are efforts at NREL, condensation on turbines and geothermal materials. Advanced Systems include hot dry rock studies and Fenton Hill flow testing. The Potpourri section concludes the proceedings with reports on low-temperature resources, market analysis, brines, waste treatment biotechnology, and Bonneville Power Administration activities. Selected papers have been indexed separately for inclusion in the Energy Science and Technology Database.

Not Available

1993-10-01

321

High-precision relocation of induced seismicity in the geothermal system below St. Gallen (Switzerland)  

NASA Astrophysics Data System (ADS)

From July to November 2013 a sequence of more than 850 events, of which more than 340 could be located, was triggered in a planned hydrothermal system below the city of St. Gallen in eastern Switzerland. Seismicity initiated on July 14 and the maximum Ml in the sequence was 3.5, comparable in size with the Ml 3.4 event induced by stimulation below Basel in 2006. To improve absolute locations of the sequence, more than 1000 P and S wave arrivals were inverted for hypocenters and 1D velocity structure. Vp of 5.6-5.8 km/s and a Vp/Vs ratio of 1.82-1.9 in the source region indicate a limestone or shale-type composition and a comparison with a lithological model from a 3D seismic model suggests that the seismically active streak (height up to 400 m) is within the Mesozoic layer. To resolve the fine structure of the induced seismicity, we applied waveform cross-correlation and double-difference algorithms. The results image a NE-SW striking lineament, consistent with a left-lateral fault plane derived from first motion polarities and moment tensor inversions. A spatio-temporal analysis of the relocated seismicity shows that, during first acid jobs on July 17, microseismicity propagated towards southwest over the entire future Ml 3.5 rupture plane. The almost vertical focal plane associated with the Ml 3.5 event of July 20 is well imaged by the seismicity. The area of the ruptured fault is approximately 675x400 m. Seismicity images a change in focal depths along strike, which correlates with a kink or bend in the mapped fault system northeast of the Ml 3.5 event. This change might indicate structural differences or a segmentation of the fault. Following the Ml 3.5 event, seismicity propagated along strike to the northeast, in a region without any mapped faults, indicating a continuation of the fault segment. Seismicity on this segment occurred in September and October. A complete rupture of the NE segment would have the potential to produce a magnitude larger than 3.0. Similarity of waveforms suggests that an Ml 3.2 in 1987 and an Ml 2.2 event in 1993 occurred on a similar structure with a similar slip direction as the Ml 3.5 event. It appears that the fault zone targeted by the geothermal project is not only oriented favourably for rupture relative to the regional stress field, but is also close to failure.

Diehl, Tobias; Kraft, Toni; Eduard, Kissling; Nicholas, Deichmann; Clinton, John; Wiemer, Stefan

2014-05-01

322

Using Electromagnetic Techniques to Test Models for Shallow Permeability in the Surprise Valley, CA Geothermal System  

NASA Astrophysics Data System (ADS)

Surprise Valley in northeastern Modoc County, CA is the westernmost major extensional graben in the northwestern Basin and Range province. There are abundant faults coincident with moderate to boiling temperature hot springs that discharge along the western rim of the valley and in the central eastern part of the valley. Fluid recharge and discharge pathways are poorly understood despite sporadic geothermal exploration, drilling, and development since the 1950's and a wide variety of academic studies that have been focused in the region. It is hypothesized that thermal fluids discharged into the basin exploit fracture permeability related to active extensional faulting along the Surprise Valley Fault (SVF), Lake City Fault Zone (LCFZ), and faults in the Hays Canyon Range (HCR). We present several fault-perpendicular Magnetotelluric profiles conducted across the LCFZ and HCR faults with the goal of imaging the orientation and extent of the geothermal reservoir that supplies the hot springs. Initial results are consistent with the HCR faults tapping a deep conductive aquifer below shallow resistive extrusive igneous rocks, with narrow low resistivity regions beneath the faults. There is no conclusive evidence for or against the LCFZ acting as a preferred fluid pathway, due to relatively homogeneous distribution highly conductive materials and the difficulty in differentiating clay-rich lacustrine sediments from hydrothermal fluids or clays.

Hawkes, S.; McClain, J. S.; Kahn, A.; Lewis, K.

2013-12-01

323

Comparing FRACHEM and TOUGHREACT for reactive transport modelingof brine-rock interactions in enhanced geothermal systems (EGS)  

SciTech Connect

Coupled modelling of fluid flow and reactive transport ingeothermal systems is challenging because of reservoir conditions such ashigh temperatures, elevated pressures and sometimes high salinities ofthe formation fluids. Thermal hydrological-chemical (THC) codes, such asFRACHEM and TOUGHREACT, have been developed to evaluate the long-termhydrothermal and chemical evolution of exploited reservoirs. In thisstudy, the two codes were applied to model the same geothermal reservoir,to forecast reservoir evolution using respective thermodynamic andkinetic input data. A recent (unreleased) TOUGHREACT version allows theuse of either an extended Debye-Hu?ckel or Pitzer activity model forcalculating activity coefficients, while FRACHEM was designed to use thePitzer formalism. Comparison of models results indicate that differencesin thermodynamic equilibrium constants, activity coefficients andkinetics models can result in significant differences in predictedmineral precipitation behaviour and reservoir-porosity evolution.Differences in the calculation schemes typically produce less differencein model outputs than differences in input thermodynamic and kineticdata, with model results being particularly sensitive to differences inion-interaction parameters for highsalinity systems.

Andre, L.; Spycher, N.; Xu, T.; Pruess, K.; Vuataz, F.-D.

2005-11-15

324

The effect of CO{sub 2} on reservoir behavior for geothermal systems  

SciTech Connect

The purpose was to gain an understanding of the effects of non-condensible gases (CO/sub 2/) in fractured two-phase geothermal systems. A thorough review of previous work on non-condensible gases was carried out. In addition, since the flowing mass fraction of CO/sub 2/ is strongly controlled by the flowing saturation, the flowing enthalpy literature was also reviewed. Numerical techniques were employed to examine how non-condensible gases (CO/sub 2/) affect well transients and to determine the value of these effects as tools to evaluate in situ reservoir parameters. Simplified reservoir models were used to define the effects of CO/sub 2/ in the reservoir and the resulting transient behavior at the feedzones to the well. Furthermore, fracture-matrix interaction was studied in detail to identify the effects of CO/sub 2/ on recovery and flow patterns within the reservoir. The insight gained from the sensitivity studies for enthalpy and CO/sub 2/ transients was applied to interpret transient data from well BR21 at the Broadlands geothermal field of New Zealand.

Gaulke, S.W.

1986-12-01

325

Evaluation of materials for systems using cooled, treated geothermal or high-saline brines  

NASA Astrophysics Data System (ADS)

Lack of adequate quantities of clean surface water for use in wet (evaporative) cooling systems indicates the use of high-salinity waste waters, or cooled geothermal brines, for makeup purposes. High-chloride, aerated water represents an extremely corrosive environment. In order to determine metals suitable for use in such an environment, metal coupons were exposed to aerated, treated geothermal brine salted to a chloride concentration of 10,000 and 50,000 ppM (mg/L) for periods of up to 30 days. The exposed coupons were evaluated to determine the general, pitting, and crevice corrosion characteristics of the metals. Results indicate that ferritic stainless steels (29-4-2 and SEACURE) exhibit excellent corrosion resistance at all levels of chloride concentration. Copper-nickel alloys (70/30 and Monel 400) exhibited excellent corrosion resistance in the high-saline water. The 70/30 copper-nickel alloy, which showed excellent resistance to general corrosion, exhibited mild pitting in the 30-day tests.

Suciu, D. F.; Wikoff, P. M.

1982-09-01

326

Thermal structure and fluid phase states in high-enthalpy geothermal systems as sensors of crustal permeability  

NASA Astrophysics Data System (ADS)

High-enthalpy geothermal systems show distinct thermal structures and fluid phase state distributions (single phase vs. boiling regions). These can be rationalized in terms of the phase diagram of water in pressure-enthalpy space (Fig. 1). Numerical simulations using the HYDROTHERM and CSMP++ simulation platforms showed that system-scale permeability and the closure of permeability at higher temperatures near the magmatic heat source are the key parameter that controls this behavior (Hayba & Ingebritsen, 1997; Driesner & Geiger, 2007). Interestingly, thermal profiles that resemble those measured in natural systems only emerged when simulations were run with constant background permeability. Depth-dependent background permeability as suggested by Ingebritsen&Manning does not lead to observed profiles. The most likely interpretation is that the depth-dependent permeability model applies to a crust that is in a steady state with respect to a competition between permeability creation by failure and permeability in response to strain and chemical fluid-rock interaction while in geothermal systems high fluid pressure leads to elevated transient permeability. We suggest that the thermal structure and fluid phase state distribution in geothermal systems are measures of the sytem-scale permeability. They may be useful in better constraining parameters of empirical permeability models.pflow paths of geothermal fluids in a pressure-enthalpy phase diagram of water as a function of permeability: (A) 10-16 m2, (B) 10-15 m2, (C) 10-14 m2.

Driesner, T.; Weis, P.

2012-12-01

327

Imaging the Roots of Geothermal Systems: 3-D Inversion of Magnetotelluric Array Data in the Taupo Volcanic Zone, New Zealand  

NASA Astrophysics Data System (ADS)

The Taupo Volcanic Zone (TVZ), located in the central North Island of New Zealand, is a rifted arc that contains more than 20 liquid-dominated high-temperature geothermal systems, which together discharge ~4.2 GW of heat at the surface. The shallow (upper ~500 m) extent of these geothermal systems is marked by low-resistivity, mapped by tens-of-thousands of DC resistivity measurements collected throughout the 1970's and 80's. Conceptual models of heat transport through the brittle crust of the TVZ link these low-resistivity anomalies to the tops of vertically ascending plumes of convecting hydrothermal fluid. Recently, data from a 40-site array of broadband seismometers with ~4 km station spacing, and an array of 270 broadband magnetotelluric (MT) measurements with ~2 km station spacing, have been collected in the south-eastern part of the TVZ in an experiment to image the deep structure (or roots) of the geothermal systems in this region. Unlike DC resistivity, these MT measurements are capable of resolving the resistivity structure of the Earth to depths of 10 km or more. 2-D and 3-D models of subsets of these MT data have been used to provide the first-ever images of quasi-vertical low-resistivity zones (at depths of 3-7 km) that connect with the near-surface geothermal fields. These low-resistivity zones are interpreted to represent convection plumes of high-temperature fluids ascending within fractures, which supply heat to the overlying geothermal fields. At the Rotokawa, Ngatamariki and Ohaaki geothermal fields, these plumes extend to a broad layer of low-resistivity, inferred to represent a magmatic, basal heat source located below the seismogenic zone (at ~7-8 km depth) that drives convection in the brittle crust above. Little is known about the mechanisms that transfer heat into the hydrothermal regime. However, at Rotokawa, new 3-D resistivity models image a vertical low-resistivity zone that lies directly beneath the geothermal field. The top of this low-resistivity zone (at ~3 km depth where temperatures are greater than 330°C) coincides with a cluster of seismicity that may mark the top of the brittle-ductile transition zone. Thus, we may be imaging the contact between the underlying ';volcanic' and the upper ';geothermal' system, at a depth (~4 km) that is much shallower than expected.

Bertrand, E. A.; Caldwell, G.; Bannister, S. C.; Hill, G.; Bennie, S.

2013-12-01

328

Technical support for geopressured-geothermal well activities in Louisiana. Final report, September 27, 1978-December 31, 1980  

SciTech Connect

The data analysis is based on the Brazoria Texas well and the balance of the modeling work is theoretical. Progress in the regional assessment of the geopressured-geothermal resource in Louisiana is reported. Environmental monitoring effort established monitoring systems and baseline environmental measurements. Efforts to improve the technoeconomic model, improve the estimates of methane in solution, and to evaluate newly identified sites are described. (MHR)

Wrighton, F.M.; Bebout, D.; Carver, D.R.; Groat, C.C.; Johnson, A.E. Jr.

1981-08-31

329

Direct Utilization of Geothermal Heat in Cascade Application to Aquaculture and Greenhouse Systems at Navarro College. Annual Report, January-December 1982.  

National Technical Information Service (NTIS)

Progress is reported on a project for the use of the 130 exp 0 F central Texas geothermal resource. The revised project consists of cascading the geothermal energy through two enclosed aquaculture ponds, a greenhouse heating system, and into a collection ...

K. Smith

1982-01-01

330

Direct utilization of geothermal heat in cascade application to aquaculture and greenhouse systems at Navarro College. Annual report, January-December 1982  

SciTech Connect

Progress is reported on a project for the use of the 130/sup 0/F central Texas geothermal resource. The revised project consists of cascading the geothermal energy through two enclosed aquaculture ponds, a greenhouse heating system, and into a collection catfish reservoir. (MHR)

Smith, K.

1982-12-31

331

Potential impacts of artificial intelligence expert systems on geothermal well drilling costs:  

SciTech Connect

The Geothermal research Program of the US Department of Energy (DOE) has as one of its goals to reduce the cost of drilling geothermal wells by 25 percent. To attain this goal, DOE continuously evaluates new technologies to determine their potential in contributing to the Program. One such technology is artifical intelligence (AI), a branch of computer science that, in recent years, has begun to impact the marketplace in a number of fields. Expert systems techniques can (and in some cases, already have) been applied to develop computer-based ''advisors'' to assist drilling personnel in areas such as designing mud systems, casing plans, and cement programs, optimizing drill bit selection and bottom hole asssembly (BHA) design, and alleviating lost circulation, stuck pipe, fishing, and cement problems. Intelligent machines with sensor and/or robotic directly linked to AI systems, have potential applications in areas of bit control, rig hydraulics, pipe handling, and pipe inspection. Using a well costing spreadsheet, the potential savings that could be attributed to each of these systems was calculated for three base cases: a dry steam well at The Geysers, a medium-depth Imerial Valley well, and a deep Imperial Valley well. Based on the average potential savings to be realized, expert systems for handling lost circulations problems and for BHA design are the most likely to produce significant results. Automated bit control and rig hydraulics also exhibit high potential savings, but these savings are extremely sensitive to the assumptions of improved drilling efficiency and the cost of these sytems at the rig. 50 refs., 19 figs., 17 tabs.

Satrape, J.V.

1987-11-24

332

Interactive Maps from the Great Basin Center for Geothermal Energy  

DOE Data Explorer

The Great Basin Center for Geothermal Energy, part of the University of Nevada, Reno, conducts research towards the establishment of geothermal energy as an economically viable energy source within the Great Basin. The Center specializes in collecting and synthesizing geologic, geochemical, geodetic, geophysical, and tectonic data, and using Geographic Information System (GIS) technology to view and analyze this data and to produce favorability maps of geothermal potential. The interactive maps are built with layers of spatial data that are also available as direct file downloads (see DDE00299). The maps allow analysis of these many layers, with various data sets turned on or off, for determining potential areas that would be favorable for geothermal drilling or other activity. They provide information on current exploration projects and leases, Bureau of Land Management land status, and map presentation of each type of scientific spatial data: geothermal, geophysical, geologic, geodetic, groundwater, and geochemical.

333

Delineation of the High Enthalpy Reservoirs of the Sierra Nevada Volcanic Geothermal System, South-Central Chile  

NASA Astrophysics Data System (ADS)

Geothermal system associated with the Pleistocene-Holocene Sierra Nevada volcano (SNVGS) in the Araucanía Region of Chile has surface manifestations from the north-western flank of the volcano, up to Manzanar and Malalcahuello. Baños del Toro, located on the northwestern flank of the volcano, has numerous fumaroles and acid pools (acid sulfate waters, T=~90°C, pH=2.1, TDS=3080 mg/L); while Aguas de la Vaca, near the base of the volcano, has a bubbling spring (chloride-sulfate waters, T=~60°C, pH=7.0, TDS=950 mg/L). Five shallow (<120m) wells (2 at Manzanar and 3 at Malalcahuello) dug and drilled in the Cautín River Valley discharge alkaline (pH= 9-10) waters with relatively low TDS (130-210mg/L). The main heat source of the geothermal system is apparently the magmatic system of the Sierra Nevada volcano. Liquiñe-Ofqui Fault Zone (LOFZ) that transects the area forms excellent conduits for the flow of the geothermal waters. The geothermal reservoirs are hosted in the volcanic rocks interceded with glacial deposits over the North Patagonian Batholith that forms an impermeable barrier, and thus constitutes the lower boundary of the geothermal system and also controls the lateral flow of the fluids. An equilibrium temperature of ~210°C is derived from gas geothermometry (CO2/Ar-H2/Ar) of the discharges at Baños del Toro. Geothermal fluids from the upflow area on the northwestern flank of the volcano migrate northwards to the Cautín River Valley. The geothermal system has a high enthalpy reservoir(s) on the northwestern flank of the Sierra Nevada volcano and low-enthalpy reservoirs in the Cautín River Valley that have been tapped to form spas at Manzanar and Malalcahuello. While sub-vertical fractures of LOFZ facilitate the recharge of the system, lateral flow of the geothermal fluids is apparently controlled by lithology; Melipueclo Pluton in particular prevents the westward flow from the upflow zone, causing the flow only northwards to Malalcahuello and subsequently westward on meeting poorly permeable Guapitrío Member of the Cura-Mallín Formation. This change in the flow direction from northwestward up to Malalcahuello to westward towards Manzanar is supported by topographic and hydrographic conditions as well, besides available geological and geophysical data. SNVGS is perhaps the most promising geothermal system in the area, considering the presence of high enthalpy reservoir and stable heat source, ideal for its development as geothermal resource. Acknowledgments: Authors would like to acknowledge the funding for this work through the PBCT PDA-07 project of CONICYT and Geothermal Program (Cátedra de Geotermia) of the Ministry of Energy and Mining, Government of Chile.

Alam, M.; Muñoz, M.; Parada, M.

2011-12-01

334

Problems of trace-element ratios and geothermometry in a gravel geothermal-aquifer system  

SciTech Connect

The system studied is a Tertiary-age, block-faulted basin in which a Pleistocene gravel bed acts as a confined aquifer and permits the lateral dispersion of the geothermal fluids. Vertical movement of the hot water is currently believed to be controlled by faults on the east side of the valley. An aerial magnetic anomaly and a Bouguer gravity anomaly appear to correspond with thoese eastern faults. Basic data on the geology and trace element halos has been presented previously. Evaluation of the mixing phenomena in this system was attempted using a dissolved silica-enthalpy graph. A chalcedony curve is also plotted. An enthalpy versus chloride plot, suggests that either conductive cooling occurs before mixing or that higher chloride content background waters are available for mixing. (MHR)

Sonderegger, J.L.; Donovan, J.J.

1982-01-01

335

Assessment of the State-Of-The-Art of Numerical Simulation of Enhanced Geothermal Systems  

SciTech Connect

The reservoir features of importance in the operation of enhanced geothermal systems are described first (Section 2). The report then reviews existing reservoir simulators developed for application to HDR reservoirs (Section 3), hydrothermal systems (Section 4), and nuclear waste isolation (Section 5), highlighting capabilities relevant to the evaluation and assessment of EGS. The report focuses on simulators that include some representation of flow in fractures, only mentioning other simulators, such as general-purpose programs or groundwater models (Section 6). Following these detailed descriptions, the report summarizes and comments on the simulators (Section 7), and recommends a course of action for further development (Section 8). The references are included in Section 9. Appendix A contains contractual information, including a description of the original and revised scope of work for this study. Appendix B presents comments on the draft report from DOE reviewer(s) and the replies of the authors to those comments. [DJE-2005

None

1999-11-01

336

Microbiological Aspects of Geothermal Energy: Influence of Microbial Activity on Scaling and Clogging in a Cold Storage  

NASA Astrophysics Data System (ADS)

The development of strategies to substantially reduce emission of greenhouse gases to the atmosphere is one of the major challenges of the next decades. Therefore, the utilization of subsurface stored energy arouses increasing interest. Corrosion and scaling are major problems in geothermal operation which create significant maintenance and cleaning costs. In the scope of the research project AquiScreen the operational reliability of geothermal used aquifer systems was investigated under microbial, geochemical, mineralogical, and petrologic aspects (see also Alawi et al.; General Assembly EGU 2010). This presentation focuses on the investigation of a cold storage in Berlin (Reichstag building, depth 30-50 m). In order to evaluate the impact of microbial processes in the low saline aquifer (see also Vetter et al.; General Assembly EGU 2010), the microbial communities of fluid and filter samples were investigated by Fluorescent in situ hybridization (FISH) and DNA fingerprinting techniques based on PCR amplified partial 16S rRNA genes. Analyses of fluid samples revealed a bacterial community dominated by iron and sulfur oxidizing bacteria closely related to Siderooxidans lithoautotrophicus, Gallionella sp. and Thiotrix unzii. Scanning electron microscope analysis revealed iron hydroxide formation and precipitation in the filter of the top side facility and the well, corresponding to the abundance of iron oxidizing bacteria. Besides oxidizing bacteria sulfate reducing bacteria (SRB) were detected as well, indicating the formation of micro-habitats with divergent redox zones. After several years of operation and routine maintenance procedures the injectivity of the injection wells and the endurance of the top side facility filters were reduced drastically due to clogging. Mechanical cleaning and a disinfection treatment with hydrogen peroxide (H2O2) were successful to re-establish the injectivity of the wells. The results of the microbiological investigations prove that bacteria and their metabolic activities were involved in the decrease of filter endurances. A strong biofilm formation of filamentous sulfur-oxidizing bacteria related to Thiothrix was observed. In the course of the disinfection measure the microbial composition in the process water changed significantly. Thiothrix could not be detected any longer and the biocoenosis in the fluid was dominated now by Flavobacterium, Acidovorax as well as Alcaligenaceae related organisms. In contrast, SRB analyzed by specific dissimilatory sulfite reductase genes were hardly affected by the disinfection measures. However, even if especially SRB are considered as the most important taxonomic group for microbiologically influenced corrosion (MIC), present operational results indicate that scaling and clogging were the predominant processes for the operation of the shallow cold storage in Berlin.

Lerm, Stephanie; Alawi, Mashal; Miethling-Graff, Rona; Vieth, Andrea; Seibt, Andrea; Wolfgramm, Markus; Würdemann, Hilke

2010-05-01

337

Oxygen isotope exchange in rocks and minerals from the Cerro Prieto geothermal system: Indicators of temperature distribution and fluid flow  

Microsoft Academic Search

Paleotemperatures different from the present thermal regime were studied by examining coexisting mineral systems which exchanged their oxygen with the geothermal brines at different rates. Oxygen isotopic compositions were measured in drill cuttings and core and core samples from more than 40 wells. Oxygen isotopic profiles of pore filling calcites in sandstones are a measure of the recent equilibrium temperature

A. E. Williams; W. A. Elders

1981-01-01

338

An integrated multidisciplinary re-evaluation of the geothermal system at Valles Caldera, New Mexico, using an immersive three-dimensional (3D) visualization environment  

NASA Astrophysics Data System (ADS)

We describe an approach to explore the spatial relationships of a geothermal resource by examining diverse geological, geophysical, and geochemical data sets using the immersive 3-dimensional (3D) visualization capabilities of the UC Davis Keck Center for Active Visualization in the Earth Sciences (KeckCAVES). The KeckCAVES is a facility where stereoscopic images are projected onto four, surfaces (three walls and a floor), which the user perceives as a seamless 3D image of the data. The user can manipulate and interact with the data, allowing a more intuitive interpretation of data set relationships than is possible with traditional 2-dimensional techniques. We incorporate multiple data sets of the geothermal system at Valles Caldera, New Mexico: topography, lithology, faults, temperature, alteration mineralogy, and magnetotellurics. With the ability to rapidly and intuitively observe data relationships, we are able to efficiently and rapidly draw conclusions about the subsurface architecture of the Valles Caldera geothermal system. We identify two high-temperature anomalies, one that corresponds with normal faults along the western caldera ring fracture, and one that with the resurgent dome. A cold-temperature anomaly identified adjacent to the resurgent dome high-temperature anomaly appears to relate to a fault controlled graben valley that acts as a recharge zone, likely funneling cold meteoric water into the subsurface along normal faults observed on published maps and cross sections. These high-temperature anomalies broadly correspond to subsurface regions where previous magnetotelluric studies have identified low apparent resistivity. Existing hot springs in the Sulfur Springs area correspond to the only location where our modeled 100°C isotherm intersects the ground surface. Correlation between the first occurrence of key alteration minerals (pyrite, chlorite, epidote) in previously drilled boreholes and our temperature model vary, with chlorite showing a strong correlation with a model temperature of ~120°C. In summary, the application of immersive 3D modeling can provide industry with a method to make informed assessments of the location and volume of a geothermal system and a cost-effective approach during exploration and developmentblique view from beneath the Valles Caldera geothermal system, visualized in the 3D immersive KeckCAVES facility at UC Davis. View is looking up to the southwest. Data from previously drilled temperature boreholes (red lines) were used to calculate temperature isotherms (100°C-blue; 150°C-green; 200°C-yellow; 250°C-red).

Fowler, A.; Bennett, S. E.; Wildgoose, M.; Cantwell, C.; Elliott, A. J.

2012-12-01

339

FINAL REPORT ENHANCED GEOTHERMAL SYSTEMS TECHNOLOGY PHASE II ANIMAS VALLEY, NEW MEXICO  

SciTech Connect

Final Technical Report covering siting, permitting, and drilling two geothermal temperature gradient holes. This report provides a summary of geotechnical and geophysical data that led to the siting, drilling, and completion of 2 temperature gradient holes in the geothermal anomaly at Lightning Dock Known Geothermal Resource Area in the Animas Valley of New Mexico. Included in this report is a summary of institutional factors and data defining the well drilling process and acquiring drilling permits. Data covering the results of the drilling and temperature logging of these two holes are provided. The two gradient holes were sited on federal geothermal leases owned by Lightning Dock Geothermal, Inc. and both holes were drilled into lakebed sediments some distance from the intense shallow geothermal anomaly located in the eastern half of Section 7, Township 25 South, Range 19 West.

Roy A.Cunniff; Roger L. Bowers

2003-12-29

340

Federal Geothermal Research Program Update Fiscal Year 2000  

SciTech Connect

The Department of Energy's Geothermal Program serves two broad purposes: (1) to assist industry in overcoming near-term barriers by conducting cost-shared research and field verification that allows geothermal energy to compete in today's aggressive energy markets; and (2) to undertake fundamental research with potentially large economic payoffs. The four categories of work used to distinguish the research activities of the Geothermal Program during FY 2000 reflect the main components of real-world geothermal projects. These categories form the main sections of the project descriptions in this Research Update. Exploration Technology research focuses on developing instruments and techniques to discover hidden hydrothermal systems and to explore the deep portions of known systems. Research in geophysical and geochemical methods is expected to yield increased knowledge of hidden geothermal systems. Reservoir Technology research combines laboratory and analytical investigations with equipment development and field testing to establish practical tools for resource development and management for both hydrothermal reservoirs and enhanced geothermal systems. Research in various reservoir analysis techniques is generating a wide range of information that facilitates development of improved reservoir management tools. Drilling Technology focuses on developing improved, economic drilling and completion technology for geothermal wells. Ongoing research to avert lost circulation episodes in geothermal drilling is yielding positive results. Conversion Technology research focuses on reducing costs and improving binary conversion cycle efficiency, to permit greater use of the more abundant moderate-temperature geothermal resource, and on the development of materials that will improve the operating characteristics of many types of geothermal energy equipment. Increased output and improved performance of binary cycles will result from investigations in heat cycle research.

Renner, J.L.

2001-08-15

341

Performance enhancement of a thermally activated cooling system using microchannel heat exchangers  

Microsoft Academic Search

In the current study a thermally activated cooling system that combines an ORC system with a vapor compression cooling cycle was developed and tested under laboratory conditions. This combined system can utilize waste heat or other thermal sources such as solar and geothermal to generate power and cooling. Hot oil with temperature up to 200 °C was used as the simulated

Hailei Wang; Richard B. Peterson

2011-01-01

342

The U.S. Department of Energy's Geothermal Reservoir Technology Program  

SciTech Connect

Geothermal reservoir engineering is an important aspect f the Department of Energy’s Geothermal Technology Division, geothermal research and development program. Reservoir engineering-related research, a component of all geosciences activities, is of particular importance in the context of Hydrothermal Reservoir Research. Three closely related research activities (Brine Injection, Reservoir Definition, and Caldera Reservoir Investigations) are now combined under the more general heading of Reservoir Technology. Scientific investigations, as part of the Salton Sea Scientific Drilling Program, also contribute greatly to the understanding of the behavior of high-temperature hydrothermal convection systems. With the creation of the Geothermal Technology Organization, where geothermal research will be cost-shard with industry, it is anticipated that a number of research topics will be brought to the point where the geothermal industry can rapidly put new technology into use. 2 tabs., 2 figs.

Mock, John E.; Blackett, Robert E.

1987-01-20

343

Microbiological Monitoring in Geothermal Plants  

Microsoft Academic Search

In the scope of the research projects ``AquiScreen'' and ``MiProTherm'' we investigated geothermally used groundwater systems under microbial, geochemical, mineralogical and petrological aspects. On one side an enhanced process understanding of engineered geothermal systems is mandatory to optimize plant reliability and economy, on the other side this study provides insights into the microbiology of terrestrial thermal systems. Geothermal systems located

M. Alawi; S. Lerm; R. Linder; A. Vetter; A. Vieth-Hillebrand; R. Miethling-Graff; A. Seibt; M. Wolfgramm; H. Wuerdemann

2010-01-01

344

Geothermal greenhouse development update  

SciTech Connect

Greenhouse heating is one of the popular applications of low-to moderated-temperature geothermal resources. Using geothermal energy is both an economical and efficient way to heat greenhouses. Greenhouse heating systems can be designed to utilize low-temperature (>50{degrees}C or 122{degrees}F) resources, which makes the greenhouse an attractive application. These resources are widespread throughout the western states providing a significant potential for expansion of the geothermal greenhouse industry. This article summarizes the development of geothermal heated greenhouses, which mainly began about the mid-1970`s. Based on a survey (Lienau, 1988) conducted in 1988 and updated in 1997, there are 37 operators of commercial greenhouses. Table 1 is a listing of known commercial geothermal greenhouses, we estimate that there may be an additional 25% on which data is not available.

Lienau, P.J. [Geo-Heat Center, Oregon Institute of Technology, Klamath Falls, OR (United States)

1997-01-01

345

Quartz dissolution and silica deposition in hot-dry-rock geothermal systems  

SciTech Connect

The kinetics of quartz dissolution control the produced fluid dissolved silica concentration in geothermal systems in which the downhole residence time is finite. The produced fluid of the Phase I, Run Segment 5 experimental Hot Dry Rock (HDR) geothermal system at Fenton Hill, NM, was undersaturated with respect to quartz in one pass through the reservoir, suggesting that the rate of granite dissolution governed the outlet dissolved silica concentration in this system. The literature data for the rate of quartz dissolution in water from 65 to 625/sup 0/C is correlated using an empirical rate law which is first order in quartz surface area and degree of undersaturation of the fluid. The Arrhenius plot (ln k vs T/sup -1/) is linear over eight orders of magnitude of the rate constant, verifying the validity of the proposed rate expression. Carefully performed quartz dissolution experiments in the present study duplicated the literature data and completed the data base in the temperature range from 150 to 250/sup 0/C. Identical experiments using crushed granite indicate that the rate of quartz dissolution in the presence of granite could be as much as 1 to 2 orders of magnitude faster than the rates observed in the pure quartz experiments. A temperature dependent HDR reservoir model incorporates the quartz dissolution rate law to simulate the dissolved silica behavior during the Fenton Hill Run Segment 5 experiment. For this low-permeability, fracture-dominated reservoir, the assumptions of one-dimensional plug flow through a vertically-inclined rectangular fracture and one-dimensional rock heat conduction perpendicular to the direction of flow are employed. These simplifications lead to an analytical solution for the temperature field in the reservoir.

Robinson, B.A.

1982-07-01

346

Geophysics of Geothermal Areas: State of the Art and Future Development  

NASA Astrophysics Data System (ADS)

In May 1980 a workshop organized by the Advanced School of Geophysics of the Ettore Majorana Center for Scientific Culture was held in Erice, Italy. The purpose was to present the state of the art and future development of geophysics as related to exploration for geothermal resources and the environmental impact of the development of geothermal systems. The workshop was addressed to “younger researchers working in scientific institutions and in public or private agencies and who are particularly interested in these aspects of the energy problem.” Fourteen formal lectures were presented to the workshop. This volume contains papers based on 10 of these lectures with a preface, forward, and introduction by the editors. The ten papers are “Heat Transfer in Geothermal Areas,” “Interpretation of Conductive Heat Flow Anomalies,” “Deep Electromagnetic Soundings in Geothermal Exploration,” “A Computation Method for dc Geoelectric Fields,” “Measurement of Ground Deformation in Geothermal Areas,” “Active Seismic Methods in Geothermal Exploration,” “The Role of Geophysical Investigations in the Discovery of the Latera Geothermal Field,” “Geothermal Resources Exploration in the European Community: The Geophysical Case,” “Activity Performed by AGIP (ENI Group) in the Field of Geothermal Energy,” and “Geothermal Exploration in the Western United States.” Six of the authors are from Italy, and one each is from Iceland, the Netherlands, West Germany, and the United States. All of the papers are in English.

Mabey, Don R.

347

Active filter system implementation  

Microsoft Academic Search

Adjustable speed AC drives with low input current THD are becoming increasingly important in industry. This article has detailed the implementation of a parallel active filter, which is integrated within a 450 kW adjustable speed drive to provide an overall system which conforms to IEEE 519, and which provides significant benefits on a system level. The design of the active

S. Bhattacharya; T. M. Frank; D. M. Divan; B. Banerjee

1998-01-01

348

REGIONAL ASSESSMENT OF EXPLORATION POTENTIAL FOR GEOTHERMAL SYSTEMS IN THE GREAT BASIN USING A GEOGRAPHIC INFORMATION SYSTEM (GIS) - Part II  

Microsoft Academic Search

A geothermal GIS covering the state of Nevada was developed last year using DOE funding at the Great Basin Center for Geothermal Energy (GBCGE). The currently proposed research will expand that GIS to cover the entire Great Basin. The objectives are fourfold: 1) integrate and evaluate new geothermal data developed by the GBCGE and other sources, 2) regionally assess the

Mark F. Coolbaugh; Gary Raines; Lisa Shevenell; Tim Minor; Don Sawatzky; Gary Oppliger

349

Geothermal Energy.  

ERIC Educational Resources Information Center

During 1978, exploration for geothermal energy continued at the same moderately low level of the past few years in most countries. The U.S. is the only country where the development of geothermal energy depends on private industry. (BB)

Reed, Marshall J.

1979-01-01

350

Geothermal Energy  

SciTech Connect

Geothermal Energy Technology (GET) announces on a bimonthly basis the current worldwide information available on the technologies required for economic recovery of geothermal energy and its use as direct heat or for electric power production.

Steele, B.C.; Harman, G.; Pitsenbarger, J. [eds.

1996-02-01

351

Mt. Natib, Philippines: a geochemical model of a caldera-hosted geothermal system  

NASA Astrophysics Data System (ADS)

Geochemical investigations have been conducted on the thermal springs within the Mt. Natib caldera, western Luzon, Philippines. The thermal waters are mostly of the SO 4-HCO 3-Cl and Cl-HCO 3 types indicating substantial contributions from condensates and meteoric water. The spatial trend in Cl/B ratios in hot springs is consistent with dominantly vertical permeability and fluid movement. Cation geothermometry indicates subsurface temperatures greater than 200°C. A chloride-enthalpy plot reveals subsurface dilution of geothermal fluid with conductively heated surface water and points to a reservoir fluid with a chloride content of 5000 mg/kg at a temperature of 170°C. This temperature estimate is considered to be conservative due to evidence of near-surface low permeability and chemical reequilibration. Finally, a physico-chemical model of the caldera-hosted hydrothermal system at Mt. Natib is presented based on the available data.

Ruaya, J. R.; Panem, C. C.

1991-04-01

352

Multielement geochemistry of solid materials in geothermal systems and its applications. Part 1. Hot-water system at the Roosevelt Hot Springs KGRA, Utah  

Microsoft Academic Search

Geochemical studies of the geothermal system at Roosevelt Hot Springs, Utah, have led to development of chemical criteria for recognition of major features of the system and to a three-dimensional model for chemical zoning in the system. Based on this improved level of understanding several new or modified geochemical exploration and assessment techniques have been defined and are probably broadly

R. W. Bamford; O. D. Christensen; R. M. Capuano

1980-01-01

353

Evaluation of materials for systems using cooled, treated geothermal or high-saline brines  

SciTech Connect

Lack of adequate quantities of clean surface water for use in wet (evaporative) cooling systems indicates the use of high-salinity waste waters, or cooled geothermal brines, for makeup purposes. High-chloride, aerated water represents an extremely corrosive environment. In order to determine metals suitable for use in such an environment, metal coupons were exposed to aerated, treated geothermal brine salted to a chloride concentration of 10,000 and 50,000 ppM (mg/L) for periods of up to 30 days. The exposed coupons were evaluated to determine the general, pitting, and crevice corrosion characteristics of the metals. The metals exhibiting corrosion resistance at 50,000 ppM chloride were then evaluated at 100,000 and 200,000 ppM chloride. Since these were screening tests to select materials for components to be used in a cooling system, with primary emphasis on condenser tubing, several materials were exposed for 4 to 10 months in pilot cooling tower test units with heat transfer for further corrosion evaluation. The results of the screening tests indicate that ferritic stainless steels (29-4-2 and SEA-CURE) exhibit excellent corrosion resistance at all levels of chloride concentration. Copper-nickel alloys (70/30 and Monel 400) exhibited excellent corrosion resistance in the high-saline water. The 70/30 copper-nickel alloy, which showed excellent resistance to general corrosion, exhibited mild pitting in the 30-day tests. This pitting was not apparent, however, after 6 months of exposure in the pilot cooling tower tests. The nickel-base alloys exhibited excellent corrosion resistance, but their high cost prevents their use unless no other material is found feasible. Other materials tested, although unsuitable for condenser tubing material, would be suitable as tube sheet material.

Suciu, D.F.; Wikoff, P.M.

1982-09-01

354

Geothermal energy: basic legal parameters  

SciTech Connect

Geothermal activity in the United States is in initial stages. Thus, the states may establish a comprehensive legal framework to guide the course of future development. For geothermal energy to supply its full potential, basic parameters must be established which identify the subject resource and provide for prompt access and secure rights to the resource. A clear understanding of the nature of geothermal development is a prerequisite for effective legislation. Geothermal resources have distinctive characteristics which should be recognized in state laws and regulations. Regulatory experience with other resources is an important reference, but may not be transferable to geothermal development. Indeed, current state and federal geothermal policies are often criticized for excessive reliance on mineral or water law precedents. In addition policies applied to deep, hot geothermal resources may be inappropriate for shallow warm thermal fluids.

Wonstolen, K.A.

1980-09-01

355

QEMSCAN° (Quantitative Evaluation of Minerals by Scanning Electron Microscopy): capability and application to fracture characterization in geothermal systems  

NASA Astrophysics Data System (ADS)

Fractures are important conduits for fluids in geothermal systems, and the creation and maintenance of fracture permeability is a fundamental aspect of EGS (Engineered Geothermal System) development. Hydraulic or chemical stimulation techniques are often employed to achieve this. In the case of chemical stimulation, an understanding of the minerals present in the fractures themselves is desirable to better design a stimulation effort (i.e. which chemical to use and how much). Borehole televiewer surveys provide important information about regional and local stress regimes and fracture characteristics (e.g. fracture aperture), and XRD is useful for examining bulk rock mineralogy, but neither technique is able to quantify the distribution of these minerals in fractures. QEMSCAN° is a fully-automated micro-analysis system that enables quantitative chemical analysis of materials and generation of high-resolution mineral maps and images as well as porosity structure. It uses a scanning electron microscopy platform (SEM) with an electron beam source in combination with four energy-dispersive X-ray spectrometers (EDS). The measured backscattered electron and electron-induced secondary X-ray emission spectra are used to classify sample mineralogy. Initial applications of QEMSCAN° technology were predominantly in the minerals industry and application to geothermal problems has remained limited to date. In this pilot study, the potential application of QEMSCAN° technology to fracture characterization was evaluated using samples of representative mineralized fractures in two geothermal systems (Newberry Volcano, Oregon and Brady's geothermal field, Nevada). QEMSCAN° results were compared with XRD and petrographic techniques. Nine samples were analyzed from each field, collected from the drill core in the 1000-1500 m depth range in two shallow wells (GEO-N2 at Newberry Volcano and BCH-3 at Brady's). The samples were prepared as polished thin sections for QEMSCAN° analysis. Results indicate that a sampling resolution of 10 ?m is sufficient to resolve fracture morphology and mineral zonation (where multiple episodes of mineralization occurred), and enables relatively fast data acquisition (3 cm2 can be analyzed in approximately 3 hours). Finer resolutions (down to 2.5 ?m) take significantly longer, but can be used to provide additional spatial detail in areas of interest after a low resolution (10 ?m) scan. Use of XRD data in conjunction with QEMSCAN° data is sometimes needed to distinguish geothermal alteration minerals with similar chemical compositions (clay minerals, micas and chlorite), however overall the technique appears to have excellent potential for geothermal applications.

Ayling, B.; Rose, P. E.; Zemach, E.; Drakos, P. S.; Petty, S.

2011-12-01

356

Idaho Geothermal Commercialization Program. Idaho geothermal handbook  

SciTech Connect

The following topics are covered: geothermal resources in Idaho, market assessment, community needs assessment, geothermal leasing procedures for private lands, Idaho state geothermal leasing procedures - state lands, federal geothermal leasing procedures - federal lands, environmental and regulatory processes, local government regulations, geothermal exploration, geothermal drilling, government funding, private funding, state and federal government assistance programs, and geothermal legislation. (MHR)

Hammer, G.D.; Esposito, L.; Montgomery, M.

1980-03-01

357

Water rock interaction and hydrothermal mineral equilibria in the Tendaho geothermal system  

NASA Astrophysics Data System (ADS)

The Tendaho geothermal system occurs within a NW-SE-trending rift basin filled with Quaternary volcanics (mainly basalts) and fluvio-lacustrine sediments. Three deep (TD-1, TD-2 and TD-3) and one shallow (TD-4) geothermal wells have been drilled. The waters of productive wells TD-1, TD-2 and TD-4 are typical Na-Cl geothermal waters with reservoir temperature ranging between 220 and 270°C. Chemical analysis of core samples (altered basalts) shows increased Ca, Fe, Mg, Al content (owing to the dissolution of plagioclase and femics and the precipitation of wairakite, laumontite, epidote, garnet, calcite and clay minerals) and decreased Na, K, Si and Ti (owing mostly to the dissolution of glass matrix). Petrographic study of cuttings and core samples shows: (1) evidence of an early stage of calcite, zeolite (wairakite or laumontite) and quartz crystallization, while calcite underwent different stages of dissolution/precipitation, possibly due to abrupt changes in pH and CO 2 partial pressure; (2) that epidote, garnet, prehnite, pyroxene and amphibole crystallization occurred after wairakite or laumontite. Chlorite is the main layered silicate in the basaltic rocks in wells TD-1 and TD-2, temperatures beyond the stability of smectite and chlorite/smectite (C/S) interlayers must have been reached. The smectites and C/S interlayers in association with chlorite in well TD-3 indicate that this well has had a more complex thermal history, with variable temperatures. The smectites occur at temperatures above 120°C, which is considered to be the threshold for the transformation of smectite to illite. No evidence of disequilibrium conditions of smectites has been found at reservoir temperatures currently present at Tendaho. Fluid inclusion data indicate heating in the well TD-1, and thermal conditions similar to the ones measured in the deepest part of well TD-2, while the uppermost part of this latter has undergone cooling. Intense cooling has affected well TD-3, drilled far from the upflow zone of the field, probably in an area characterized by self-sealing, cooling and very low permeability.

Gianelli, Giovanni; Mekuria, Negussie; Battaglia, Stefano; Chersicla, Alessandro; Garofalo, Paolo; Ruggieri, Giovanni; Manganelli, Mirco; Gebregziabher, Zewde

1998-11-01

358

Modifications for Geothermal-Heating System for Kingswood Apartments, Klamath Falls, Oregon.  

National Technical Information Service (NTIS)

The Kingswood Apartments, located on Eberlein Street in Klamath Falls, are currently heated by a geothermal well producing 118 exp 0 F water. Geothermal water from the well is piped directly through fan coil units in each of the 117 apartments and dispose...

1982-01-01

359

Behavior of Rare Earth Elements in Geothermal Systems: A New Exploration/Exploitation Tool.  

National Technical Information Service (NTIS)

The goal of this four-year project was to provide a database by which to judge the utility of the rare earth elements (REE) in the exploration for and exploitation of geothermal fields in the United States. Geothermal fluids from hot springs and wells hav...

S. A. Wood

2001-01-01

360

Behavior of Rare Earth Element In Geothermal Systems; A New Exploration\\/Exploitation Tool  

Microsoft Academic Search

The goal of this four-year project was to provide a database by which to judge the utility of the rare earth elements (REE) in the exploration for and exploitation of geothermal fields in the United States. Geothermal fluids from hot springs and wells have been sampled from a number of locations, including: (1) the North Island of New Zealand (1

Scott A. Wood

2002-01-01

361

Potential Impacts of Artificial Intelligence Expert Systems on Geothermal Well Drilling Costs: Final Report.  

National Technical Information Service (NTIS)

The Geothermal research Program of the US Department of Energy (DOE) has as one of its goals to reduce the cost of drilling geothermal wells by 25 percent. To attain this goal, DOE continuously evaluates new technologies to determine their potential in co...

J. V. Satrape

1987-01-01

362

Accelerated Geothermal Resource Development in the Great Basin Through Enhanced Public Awareness and Outreach to Shareholders.  

SciTech Connect

The Great Basin Center for Geothermal Energy conducted work encompassing two main tasks. We (1) produced a web-based, stakeholder geothermal information system for Nevada geothermal data relevant to assessing and developing geothermal resources, and (2) we held informational stakeholder workshops (both as part of GeoPowering the West Initiative). The objective of this grant was to conduct workshops and fund database and web development activities. This grant funds salaries for web and database developers and part of the administrative assistant who helps to coordinate and organize workshops, and maintain selected databases.

Taranik, James V.; Oppliger, Gary; Sawatsky, Don

2002-04-10

363

Multidisciplinary research of geothermal modeling  

NASA Astrophysics Data System (ADS)

KEYWORDS Geothermal sciences, geothermics, research, theory and application, numerical calculation, geothermal modeling, Technical University Darmstadt, Ministry of Economics and Technology (BMWi) INTRODUCTION In times of global warming renewable, green energies are getting more and more important. The development of application of geothermal energy as a part of renewable energies in Germany is a multidisciplinary process of fast growing research and improvements. Geothermal energy is the energy, which is stored below earth's surface. The word geothermal derives from the Greek words geo (earth) and thermos (heat), so geothermal is a synonym to earth heat. Geothermal energy is one of the auspicious renewable energies. In average the temperature increases 3°C every 100 m of depth, which is termed as geothermal gradient. Therefore 99 percent of our planet is hotter than 1.000°C, while 99 percent of that last percent is even hotter than 100°C. Already in a depth of about 1 kilometer temperatures of 35 - 40°C can be achieved. While other renewable energies arise less or more from the sun, geothermal energy sources its heat from the earth's interior, which is caused mostly by radioactive decay of persistent isotopes. This means a possibility of a base-loadable form of energy supply. Especially efficient is the use of deep geothermal energy of high-enthalpie reservoirs, which means a high energy potential in low depths. In Germany no high-enthalpie reservoirs are given. To use the given low-enthalpie potential and to generate geothermal power efficiently inventions and improvements need to be performed. An important part of geothermal progresses is performed by universities with multidisciplinary research of geothermal modeling. Especially in deep geothermal systems numerical calculations are essential for a correct dimensioning of the geothermal system. Therefore German universities and state aided organizations are developing numerical programs for a detailed use of application on geothermal systems. The history of this multidisciplinary research of geothermal modeling performed by German universities is shown in this paper. Outstanding geothermal research programs of German universities and state aided organizations (BGR, LBEG, GGA) are pointed out. Actual geothermal modeling programs based on the Finite-Element-Method or the Finite-Differences-Method as well as analytical programs are introduced. National and international geothermal projects supported by German universities and state aided organizations are described. Examples of supervised shallow and deep geothermal systems are given. Actually the Technical University Darmstadt is performing a research program supported by a national organization, the Ministry of Economics and Technology (BMWi). Main aim of this research program titled experimental investigation for the verification of a Finite-Element-Multiphase-Model is to analyze the subsoil as a three-phases-model with separated consideration of conduction, convection and advection and their subsequent interaction. The latest developments of numerical projects as well as the actual state of the before mentioned research program are pointed out in the paper. REFERENCES Quick, H., Arslan, U., Meißner, S., Michael, J. 2007. Deep foundations and geothermal energy - a multi-purpose solution, IFHS: 8. International conference on multi-purpose high-rise towers and tall buildings, Abu Dhabi, 2007 Arslan, U. and Huber, H. 2008. Application of geothermal energy. University of Istanbul, Yapistanbul No. 3 / 2008, Turkey, 2008 Quick, Q., Michael, J., Arslan, U., Huber, H. 2010. History of International Geothermal Power Plants and Geothermal Projects in Germany, Proceedings World Geothermal Congress 2010 Bali, Indonesia, 25-29 April 2010 Arslan, U., Huber, H. 2010. Education of Geothermal Sciences in Germany as part of an application orientated research, Proceedings European Civil Engineering Education and Training (EUCEET III) Special Volume, 2010

-Ing. Ulvi Arslan, Univ., ., Dr. _., Prof.; Heiko Huber, Dipl.-Ing.

2010-05-01

364

Structural control on geothermal circulation in the Cerro Tuzgle-Tocomar geothermal volcanic area (Puna plateau, Argentina)  

NASA Astrophysics Data System (ADS)

The reconstruction of the stratigraphical-structural framework and the hydrogeology of geothermal areas is fundamental for understanding the relationships between cap rocks, reservoir and circulation of geothermal fluids and for planning the exploitation of the field. The Cerro Tuzgle-Tocomar geothermal volcanic area (Puna plateau, Central Andes, NW Argentina) has a high geothermal potential. It is crossed by the active NW-SE trans-Andean tectonic lineament known as the Calama-Olacapato-Toro (COT) fault system, which favours a high secondary permeability testified by the presence of numerous springs. This study presents new stratigraphic and hydrogeological data on the geothermal field, together with the analysis from remote sensed image analysis of morphostructural evidences associated with the structural framework and active tectonics. Our data suggest that the main geothermal reservoir is located within or below the Pre-Palaeozoic-Ordovician basement units, characterised by unevenly distributed secondary permeability. The reservoir is recharged by infiltration in the ridges above 4500 m a.s.l., where basement rocks are in outcrop. Below 4500 m a.s.l., the reservoir is covered by the low permeable Miocene-Quaternary units that allow a poor circulation of shallow groundwater. Geothermal fluids upwell in areas with more intense fracturing, especially where main regional structures, particularly NW-SE COT-parallel lineaments, intersect with secondary structures, such as at the Tocomar field. Away from the main tectonic features, such as at the Cerro Tuzgle field, the less developed network of faults and fractures allows only a moderate upwelling of geothermal fluids and a mixing between hot and shallow cold waters. The integration of field-based and remote-sensing analyses at the Cerro Tuzgle-Tocomar area proved to be effective in approaching the prospection of remote geothermal fields, and in defining the conceptual model for geothermal circulation.

Giordano, Guido; Pinton, Annamaria; Cianfarra, Paola; Baez, Walter; Chiodi, Agostina; Viramonte, José; Norini, Gianluca; Groppelli, Gianluca

2013-01-01

365

User manual for GEOCITY: A computer model for cost analysis of geothermal district-heating-and-cooling systems. Volume 1: Main text  

NASA Astrophysics Data System (ADS)

The cost of residential space heating, space cooling, and sanitary water heating or process heating (cooling) using geothermal energy from a hydrothermal reservoir was calculated. The GEOCITY simulates the complete geothermal heating and cooling system, which consists of two principal parts: the reservoir and fluid transmission system and the distribution system. Geothermal space heating is provided by circulating hot water through radiators, convectors, and fan-coil units. Geothermal process heating is provided by directly using the hot water or by circulating it through a process heat exchanger. The life cycle cost of thermal energy from the reservoir and fluid transmission system to the distribution system and the life cycle cost of heat (chill) to the end users are calculated by discounted cash flow analysis.

Huber, H. D.; Fassbender, L. L.; Bloomster, C. H.

1982-09-01

366

Novel thermophilic sulfate-reducing bacteria from a geothermally active underground mine in Japan.  

PubMed

Thermophilic sulfate-reducing bacteria were enriched from samples obtained from a geothermal underground mine in Japan. The enrichment cultures contained bacteria affiliated with the genera Desulfotomaculum, Thermanaeromonas, Thermincola, Thermovenabulum, Moorella, "Natronoanaerobium," and Clostridium. Two novel thermophilic sulfate-reducing strains, RL50JIII and RL80JIV, affiliated with the genera Desulfotomaculum and Thermanaeromonas, respectively, were isolated. PMID:16672530

Kaksonen, Anna H; Plumb, Jason J; Robertson, Wendy J; Spring, Stefan; Schumann, Peter; Franzmann, Peter D; Puhakka, Jaakko A

2006-05-01

367

Changing hydrothermal activity in the Atlantis II Deep geothermal system  

Microsoft Academic Search

THE Atlantis II Deep is a pool of hot saline brine at the bottom of the central rift in the Red Sea (Fig. 1). Since its discovery in 1965 (ref. 1) it has undergone repeated detailed investigations2,3. A permanent increase of temperature has been reported by many workers4-8 and was interpreted as the result of the injection of hot brine

M. Schoell; M. HARTMANN

1978-01-01

368

GeoSys.Chem: Estimate of reservoir fluid characteristics as first step in geochemical modeling of geothermal systems  

NASA Astrophysics Data System (ADS)

A computer code GeoSys.Chem for the calculation of deep geothermal reservoir fluid characteristics from the measured physical-chemical parameters of separated water and condensed vapor samples obtained from drilled wells is presented. It was written as a dynamic link library (DLL) in Visual Basic in Visual Studio 2010 (VB.NET). Using this library a demonstration program GeoChem was developed in VB.NET, which accepts the input data file in the XML format. A stepwise calculation of deep reservoir fluid characteristics of 11 production wells of Los Azufres geothermal system is performed. The calculated concentration of CO2 (e.g.=1270 mmole/kg in the well AZ-09) in the vapor, discharged into the atmosphere at the weir box, from the water sample indicates some problem in the analysis of carbonic species concentrations. In the absence of good quality analysis of carbonic species it is suggested to consider the CO2 in the vapor sample at the separator and the total dissolved carbonic species concentration in the water sample (i.e., without considering the liberation of CO2 in the atmospheric vapor at the weir box) for the geothermal reservoir fluid composition calculations. Similarly, it presents various diagrams developed in Excel for the thermodynamic evolution of Los Azufres geothermal reservoir.

Verma, Mahendra P.

2012-12-01

369

Geochemical Enhancement Of Enhanced Geothermal System Reservoirs: An Integrated Field And Geochemical Approach  

SciTech Connect

The geochemical effects of injecting fluids into geothermal reservoirs are poorly understood and may be significantly underestimated. Decreased performance of injection wells has been observed in several geothermal fields after only a few years of service, but the reasons for these declines has not been established. This study had three primary objectives: 1) determine the cause(s) of the loss of injectivity; 2) utilize these observations to constrain numerical models of water-rock interactions; and 3) develop injection strategies for mitigating and reversing the potential effects of these interactions. In this study rock samples from original and redrilled injection wells at Coso and the Salton Sea geothermal fields, CA, were used to characterize the mineral and geochemical changes that occurred as a result of injection. The study documented the presence of mineral scales and at both fields in the reservoir rocks adjacent to the injection wells. At the Salton Sea, the scales consist of alternating layers of fluorite and barite, accompanied by minor anhydrite, amorphous silica and copper arsenic sulfides. Amorphous silica and traces of calcite were deposited at Coso. The formation of silica scale at Coso provides an example of the effects of untreated (unacidified) injectate on the reservoir rocks. Scanning electron microscopy and X-ray diffractometry were used to characterize the scale deposits. The silica scale in the reservoir rocks at Coso was initially deposited as spheres of opal-A 1-2 micrometers in diameter. As the deposits matured, the spheres coalesced to form larger spheres up to 10 micrometer in diameter. Further maturation and infilling of the spaces between spheres resulted in the formation of plates and sheets that substantially reduce the original porosity and permeability of the fractures. Peripheral to the silica deposits, fluid inclusions with high water/gas ratios provide a subtle record of interactions between the injectate and reservoir rocks. In contrast, fluid inclusions trapped prior to injection are relatively gas rich. These results suggest that the rocks undergo extensive microfracturing during injection and that the composition of the fluid inclusions will be biased toward the youngest event. Interactions between the reservoir rocks and injectate were modeled using the non-isothermal reactive geochemical transport code TOUGHREACT. Changes in fluid pH, fracture porosity, fracture permeability, fluid temperature, and mineral abundances were monitored. The simulations predict that amorphous silica will precipitate primarily within a few meters of the injection well and that mineral deposition will lead to rapid declines in fracture porosity and permeability, consistent with field observations. In support of Enhanced Geothermal System development, petrologic studies of Coso well 46A-19RD were conducted to determine the regions that are most likely to fail when stimulated. These studies indicate that the most intensely brecciated and altered rocks in the zone targeted for stimulation (below 10,000 ft (3048 m)) occur between 11,200 and 11,350 ft (3414 and 3459 m). This zone is interpreted as a shear zone that initially juxtaposed quartz diorite against granodiorite. Strong pervasive alteration and veining within the brecciated quartz diorite and granodiorite suggest this shear zone was permeable in the past. This zone of weakness was subsequently exploited by a granophyre dike whose top occurs at 11,350 ft (3459 m). The dike is unaltered. We anticipate, based on analysis of the well samples that failure during stimulation will most likely occur on this shear zone.

Joseph N. Moore

2007-12-31

370

Geothermal Energy Photo Collections: Links from the DOE Geothermal Technologies Program.  

DOE Data Explorer

The Geothermal Technologies Program, part of DOE's Office of Energy Efficiency and Renewable Energy, provides a page of links to online resources for photos of geothermal energy technologies, applications, projects, resources, and attractions. Resources currently listed are: • Geothermal Education Office Slide Show (100 photos of geothermal energy technologies and applications) • International Geothermal Association (photos from around the world of geothermal development activities) • National Renewable Energy Laboratory Photographic Information Exchange (PIX) • Salton Sea Photo Gallery • Yellowstone Geothermal Features • U.S. Geological Survey Cascades Volcano Observatory Photo Archives • Volcanoes of the Alaska Pennisula and Aleutian Islands (Selected Photographs from U.S.G.S.) • Volcanoes of Hawaii (U.S.G.S.)

371

INVESTIGATION OF AN ELECTROCHEMICAL MONITOR FOR TRACKING BIOFILM DEVELOPMENT AT THE BONNETT GEOTHERMAL PLANT, COVE FORT, UTAH  

Microsoft Academic Search

The investigation of an electrochemical probe for the real-time monitoring of biofilm develop- ment in a geothermal plant cooling system is reported. For the study, a BIGEORGE Biofilm Activity Monitoring System was installed in a cooling water circulation line at the Bonnett Geothermal Plant near Cove Fort, Utah. Data collected from the instrument from December 2000 to March 2002 has

P. A. Pryfogle; G. L. Mines; T. L. Sperry; R. G. Allred

372

Identification of Solid Wastes in Geothermal Operations.  

National Technical Information Service (NTIS)

Regulations governing the disposal of hazardous wastes led to an assessment for geothermal solid wastes for potentially hazardous characteristics. Samples were collected from three active geothermal sites in the western United States: The Geysers, Imperia...

E. L. Hagmann D. D. Minicucci C. D. Wolbach

1981-01-01

373

ANALYSIS OF GEOTHERMAL WASTES FOR HAZARDOUS COMPONENTS  

EPA Science Inventory

Regulations governing the disposal of hazardous wastes led to an assessment for geothermal solid wastes for potentially hazardous properties. Samples were collected from three active geothermal sites in the western United States: The Geysers, Imperial Valley, and northwestern Nev...

374

Exploring for Geothermal Resources with Electromagnetic Methods  

NASA Astrophysics Data System (ADS)

Electrical conductivity of the subsurface is known to be a crucial parameter for the characterization of geothermal settings. Geothermal systems, composed by a system of faults and/or fractures filled with conducting geothermal fluids and altered rocks, are ideal targets for electromagnetic (EM) methods, which have become the industry standard for exploration of geothermal systems. This review paper presents an update of the state-of-the-art geothermal exploration using EM methods. Several examples of high-enthalpy geothermal systems as well as non-volcanic systems are presented showing the successful application of EM for geothermal exploration but at the same time highlighting the importance of the development of conceptual models in order to avoid falling into interpretation pitfalls. The integration of independent data is key in order to obtain a better understanding of the geothermal system as a whole, which is the ultimate goal of exploration.

Muñoz, Gerard

2014-01-01

375

Microseismic Activity in Low-Hazard Geothermal Settings in Southern Germany  

NASA Astrophysics Data System (ADS)

In the last few years several geothermal power plants have taken up production in southern Germany and many more are currently in exploration or construction stages. One of the most promising areas in Germany with respect to geothermal exploitation is the Bavarian Molasse Basin: A karstified limestone formation at a few kilometers depth provides sufficiently high temperatures also for power production and its high permeability obviates the need for hydraulic stimulation of the reservoir. Furthermore the local setting is being considered as generally aseismic with very sparse and weak seismicity. The seismic hazard going along with production is therefore being considered negligible and no particular efforts for seismic monitoring were made. In 2008, however, an unexpected Ml 2.3 event which was felt by locals attracted public attention. With no stations near the epicenter, the event still was located in the general vicinity of a geothermal plant that took up production about half a year earlier. In the last two years a temporary network was set up that recorded more than thirty events with magnitudes mainly ranging from Ml 0 to 1.5. The data recorded in the local network are used for absolute locations. A high resolution 3-D P-wave velocity model is constructed from data of a dense 3-D seismic survey conducted to image the geothermal reservoir. An S-wave velocity model is compiled from converted shear waves, an old survey with shear wave excitation and cluster analysis of Vp/Vs ratios using the recorded events. Results show the hypocenters close to the bottom of the injection well. Results of waveform similarity analysis and clustering of events are presented along with preliminary results of further work focusing on hypocenter relocation via master-slave analysis and differential location techniques. Still, the exact extent of the man-made influence on the seismicity remains arguable. Events below magnitude 1.5 could not be detected prior to the production of the geothermal plant in the main network of the local earthquake service. Questions also remain as to the unique features of this geothermal site in comparison with others not far away that do not produce notable induced seismicity. How the fault targeted by the well is oriented in the present-day stress field is suspected to have a major impact on fault reactivation. An upcoming field experiment is about to address these open questions and test some working hypotheses. It is located at another geothermal reservoir in a very similar setting where a geothermal power plant is currently in the construction stage. In addition to monitoring the production stage, we intend to collect one year of pre-production data of the unperturbed reservoir. This will enable us to better assess the influence of fluid injections on local seismicity at geothermal plants and will lead to a better understanding of the reasons for the observed microseismicity.

Megies, T.; Wassermann, J. M.

2010-12-01

376

Evaluation of Oil-Industry Stimulation Practices for Engineered Geothermal Systems  

SciTech Connect

Geothermal energy extraction is typically achieved by use of long open-hole intervals in an attempt to connect the well with the greatest possible rock mass. This presents a problem for the development of Enhanced (Engineered) Geothermal Systems (EGS), owing to the challenge of obtaining uniform stimulation throughout the open-hole interval. Fluids are often injected in only a fraction of that interval, reducing heat transfer efficiency and increasing energy cost. Pinnacle Technologies, Inc. and GeothermEx, Inc. evaluated a variety of techniques and methods that are commonly used for hydraulic fracturing of oil and gas wells to increase and evaluate stimulation effectiveness in EGS wells. Headed by Leen Weijers, formerly Manager of Technical Development at Pinnacle Technologies, Inc., the project ran from August 1, 2004 to July 31, 2006 in two one-year periods to address the following tasks and milestones: 1) Analyze stimulation results from the closest oil-field equivalents for EGS applications in the United States (e.g., the Barnett Shale in North Texas) (section 3 on page 8). Pinnacle Technologies, Inc. has collected fracture growth data from thousands of stimulations (section 3.1 on page 12). This data was further evaluated in the context of: a) Identifying techniques best suited to developing a stimulated EGS fracture network (section 3.2 on page 29), and b) quantifying the growth of the network under various conditions to develop a calibrated model for fracture network growth (section 3.3 on page 30). The developed model can be used to design optimized EGS fracture networks that maximize contact with the heat source and minimize short-circuiting (section 3.4 on page 38). 2) Evaluate methods used in oil field applications to improve fluid diversion and penetration and determine their applicability to EGS (section 4 on page 50). These methods include, but are not limited to: a) Stimulation strategies (propped fracturing versus water fracturing versus injecting fluid below fracturing gradients) (section 4.1 on page 50); b) zonal isolation methods (by use of perforated casing or packers) (section 4.2 on page 57); c) fracture re-orientation and fracture network growth techniques (e.g., by use of alternating high- and low-rate injections) (section 4.4 on page 74); and d) fluid diversion methods (by use of the SurgiFrac technique, the StimGun perforation technique, or stress shadowing). This project task is to be completed in the first project year, enabling the most promising techniques to be field tested and evaluated in the second project year. 3) Study the applicability of the methods listed above by utilizing several techniques (section 5 on page 75) including, but not limited to: a) Hydraulic Impedance Testing (HIT) to determine the location of open hydraulic fractures along a open-hole interval; b) pressure transient testing to determine reservoir permeability, pore pressure, and closure stress; and c) treatment well tilt mapping or microseismic mapping to evaluate fracture coverage. These techniques were reviewed for their potential application for EGS in the first project year (section 5.1 on page 75). This study also includes further analysis of any field testing that will be conducted in the Desert Peak area in Nevada for ORMAT Nevada, Inc. (section 5.2 on page 86), with the aim to close the loop to provide reliable calibrated fracture model results. Developed through its hydraulic fracture consulting business, techniques of Pinnacle Technologies, Inc. for stimulating and analyzing fracture growth have helped the oil and gas industry to improve hydraulic fracturing from both a technical and economic perspective. In addition to more than 30 years of experience in the development of geothermal energy for commercial power generation throughout the world, GeothermEx, Inc. brings to the project: 1) Detailed information about specific developed and potential EGS reservoirs, 2) experience with geothermal well design, completion, and testing practices, and 3) a direct connection to the Desert Peak EGS project.

Peter Van Dyke; Leen Weijers; Ann Robertson-Tait; Norm Warpinski; Mike Mayerhofer; Bill Minner; Craig Cipolla

2007-10-17

377

Numerical simulations of heat transfer considering hydraulic discontinuity for an enhanced geothermal system development in Seokmo Island, Korea  

NASA Astrophysics Data System (ADS)

The construction of the first geothermal plant in Korea is under planning in Seokmo Island, where a few artesian wells showing relatively high water temperature of around 70 degrees were discovered lately. Geologic structure in this region is characterized by the fractured granite. Numerical simulations for the temperature evolution in a fractured geothermal reservoir in Seokmo Island under the supposed injection-extraction operating conditions were carried out using TOUGH2. A MINC model including a hydraulic discontinuity in Seokmo Island region, which reflected the analysis from several geophysical explorations and drilled rock core, was generated. Supposing the N05°E, NW83° fracture zone containing the pumping range, the numerical simulation results show that temperature of the extracted geothermal water decreases after 15 years of operation, which decreases the overall efficiency of the expected geothermal plant. This is because the colder water from the injection well, which is 400 m apart, begins to flow into the more permeable fracture zone from the 15th year, resulting in a decrease in temperature near the pumping well. Temperature distribution calculated from the simulation also shows a rise of relatively hot geothermal water along the fracture plane. All of the results are different from the non-fracture MINC model, which shows a low temperature contour in concentric circle shape around the injection well and relatively consistent extracting temperature. This demonstrates that the distribution and the structure of fracture system influence the major mass and heat flow mechanisms in geologic medium. Therefore, an intensive geologic investigation for the fractures including their structure, permeability and connecting relation is important. Acknowledgement This study was financially supported by KIGAM, KETEP and BK21.

Shin, J.; Kim, K.; Hyun, Y.; Lee, K.; Lee, T.

2011-12-01

378

State-of-the-art hydrogen sulfide control for geothermal energy systems: 1979  

SciTech Connect

Existing state-of-the-art technologies for removal of hydrogen sulfide are discussed along with a comparative assessment of their efficiencies, reliabilities and costs. Other related topics include the characteristics of vapor-dominated and liquid-dominated resources, energy conversion systems, and the sources of hydrogen sulfide emissions. It is indicated that upstream control technologies are preferred over downsteam technologies primarily because upstream removal of hydrogen sulfide inherently controls all downstream emissions including steam-stacking. Two upstream processes for vapor-dominated resources appear promising; the copper sulfate (EIC) process, and the steam converte