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1

PREPRODUCTION ACTIVITY IMPACTS OF ENHANCED GEOTHERMAL SYSTEMS  

Microsoft Academic Search

Research into the sustainability of geothermal energy previously focused on the management and use of the resource (Rybach and Mongillo, 2006) and the environmental impacts during geothermal energy production (Bloomfield et al., 2003; Reed and Renner, 1995). Within these constraints, studies have shown that there will be less impact on air emissions (including greenhouse gases), water consumption, and land use

Corrie Clark

2

Application of Fluid-Chemistry Studies to a Hot-Dry-Rock Geothermal System: I. Neutron-Activation Studies.  

National Technical Information Service (NTIS)

Neutron activation analysis methods were developed for determination of element concentrations in geothermal system waters, bulk rock samples, separated mineral phases, and intergranular salts from a hot dry rock geothermal system. Selected trace and majo...

R. Vidale I. Binder A. Gancarz

1981-01-01

3

DEPRESSURIZATION AS A STRATEGY FOR MINING ORE BODIES WITHIN AN ACTIVE GEOTHERMAL SYSTEM  

Microsoft Academic Search

The Lihir Gold Mine in Papua New Guinea is a world-class open pit gold mine that contains an active geothermal system. Temperatures within the ore bodies are up to 200°C and this presents a major constraint to mining operations and creates the potential for geothermal hazards including hydrothermal eruptions. For mining to be feasible, it is necessary to depressurize and

Romeo Rodriguez; Zosimo Aunzo; Jacqueline Kote; Samuel Gumo

2008-01-01

4

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

5

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

6

Sensitivity of predicted scaling and permeability in Enhanced Geothermal Systems to Thermodynamic Data and Activity Models  

NASA Astrophysics Data System (ADS)

A consortium of research groups from ETH Zurich, EPF Lausanne, the Paul Scherrer Institut and the University of Bonn collaborates in a comprehensive program of basic research on key aspects of the Enhanced Geothermal Systems (EGSs). As part of this GEOTHERM project (www.geotherm.ethz.ch), we concentrate on the fundamental investigation of thermodynamic models suitable for describing fluid-rock interactions at geothermal conditions. Predictions of the fluid-rock interaction in EGS still face several major challenges. Slight variations in the input thermodynamic and kinetic parameters may result in significant differences in the predicted mineral solubilities and stable assemblage. Realistic modeling of mineral precipitation in turn has implications onto our understanding of the permeability evolution of the geothermal reservoir, as well as the scaling in technical installations. In order to reasonably model an EGS, thermodynamic databases and activity models must be tailored to geothermal conditions. We therefore implemented in GEMS code the Pitzer formalism, which is the standard model used for computing thermodynamic excess properties of brines at elevated temperatures and pressures. This model, however, depends on a vast amount of interaction parameters, which are to a substantial extend unknown. Furthermore, a high order polynomial temperature interpolation makes extrapolation unreliable if not impossible. As an alternative we additionally implemented the EUNIQUAC activity model. EUNIQUAC requires fewer empirical fit parameters (only binary interaction parameters needed) and uses simpler and more stable temperature and pressure extrapolations. This results in an increase in computation speed, which is of crucial importance when performing coupled long term simulations of geothermal reservoirs. To achieve better performance under geothermal conditions, we are currently partly reformulating EUNIQUAC and refitting the existing parameter set. First results of the Pitzer-EUNIQUAC benchmark applied to relevant aqueous solutions at elevated temperature, pressure and ionic strength will be presented.

Hingerl, Ferdinand F.; Wagner, Thomas; Kulik, Dmitrii A.; Kosakowski, Georg; Driesner, Thomas; Thomsen, Kaj

2010-05-01

7

Geochemistry and alteration facies associated with epithermal precious metal mineralization in an active geothermal system, northern Lesbos, Greece  

Microsoft Academic Search

Hydrothermal quartz veins associated with gold and silver mineralization and variable amounts of base metal sulfides have been discovered within an active geothermal system in the Megala Therma area of northern Lesbos. This geothermal system is probably a late evolutionary stage in the formation of this mineralization. The veins are hosted in Upper Miocene volcanic rocks of andesitic composition and

E. Kontis; A. E. Kelepertsis; S. Skounakis

1994-01-01

8

Seismicity Associated with Geothermal Systems  

Microsoft Academic Search

Studying natural and induced seismicity associated with geothermal systems can provide information regarding the location and magnitude of hydraulic fracturing. Understanding the fracture system can aide geothermal exploration. In addition, seismicity can affect the output of a geothermal reservoir, and potentially be a seismic hazard to the surrounding area. This study focuses on two geothermal systems: the Raft River Geothermal

R. Walters; K. van Wijk

2009-01-01

9

Sensitivity of predicted scaling and permeability in Enhanced Geothermal Systems to Thermodynamic Data and Activity Models  

Microsoft Academic Search

A consortium of research groups from ETH Zurich, EPF Lausanne, the Paul Scherrer Institut and the University of Bonn collaborates in a comprehensive program of basic research on key aspects of the Enhanced Geothermal Systems (EGSs). As part of this GEOTHERM project (www.geotherm.ethz.ch), we concentrate on the fundamental investigation of thermodynamic models suitable for describing fluid-rock interactions at geothermal conditions.

Ferdinand F. Hingerl; Thomas Wagner; Dmitrii A. Kulik; Georg Kosakowski; Thomas Driesner; Kaj Thomsen

2010-01-01

10

Seismicity Associated with Geothermal Systems  

NASA Astrophysics Data System (ADS)

Studying natural and induced seismicity associated with geothermal systems can provide information regarding the location and magnitude of hydraulic fracturing. Understanding the fracture system can aide geothermal exploration. In addition, seismicity can affect the output of a geothermal reservoir, and potentially be a seismic hazard to the surrounding area. This study focuses on two geothermal systems: the Raft River Geothermal System (RRGS) in southern Idaho and the Mt. Princeton Geothermal System (MPGS) in central Colorado. The seismic data analyzed for the RRGS is from broadband sensors that are a part of the EarthScope Project’s Transportable Array (TA), while the seismic data from the MPGS is from broadband and short-period sensors from the IRIS PASSCAL Instrument Center. A significant increase in seismic activity was measured on the TA station L14A near the RRGS, indicating pump testing and production caused induced seismicity. In Colorado, local events were identified, possibly related to natural hydraulic fracturing caused by near-surface hot fluid movement. Number of seismic events that occurred before and during the production of energy at the Raft River Geothermal System, ID. These events were at least 80 times greater than the average background noise.

Walters, R.; van Wijk, K.

2009-12-01

11

Origin and distribution of thiophenes and furans in gas discharges from active volcanoes and geothermal systems.  

PubMed

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 C(2)-C(20) 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 C(4)H(8)O, 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. PMID:20480029

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

2010-03-31

12

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

13

Concepts, Classification, and Chemistry of Geothermal Systems  

NASA Astrophysics Data System (ADS)

Main concepts and a classification of different types of geothermal systems are presented in this chapter. Particular attention is given to chemical, physical, and geometric features of the geothermal systems inferred from active geothermal areas or reconstructed from geological observations. Additionally, different types of water existing in geothermal reservoirs worldwide are reviewed here. They are discussed and related to the basic processes that dominate their chemistry. The chemistry of geothermal waters discharged from wells provides specific information about the deep fluids in geothermal systems and how they relate to natural discharges from springs at Earths surface. This knowledge can be used to obtain essential information about reservoir behavior before and during exploitation and to set up conceptual models of reservoirs. Derivation of the hydrologic and chemical structure of geothermal systems forms the basis for reactive transport simulation, here and in general.

Kühn, Michael

14

Geothermal Technologies Program: Enhanced Geothermal Systems.  

National Technical Information Service (NTIS)

This general publication describes enhanced geothermal systems (EGS) and the principles of operation. It also describes the DOE program R&D efforts in this area, and summarizes several projects using EGS technology.

2004-01-01

15

Geothermal systems and their energy resources  

Microsoft Academic Search

Geothermal systems have not been reviewed comprehensively in previous IUGG Quadrennial Reports, although thermal aspects of the shallow crust were considered by Diment (1975). Nearly all types of geothermal systems are reviewed in this report, with emphasis on U. S. systems that are most likely to be utilized as energy sources. Active volcanism and the generation and evolution of magma

Donald E. White; Marianne Guffanti

1979-01-01

16

Active Seismics to Determine Reservoir Characteristics of a Hot Dry Rock Geothermal System  

SciTech Connect

Since 1981 three wells have been drilled to depths of between 2.0 and 2.6 km in the Carnmenellis granite, Cornwall, England in order to create a HDR geothermal system. These wells are separated by between 150 and 300 m and have been hydraulically connected by massive injections of both water and viscous gel (50 cpoise). Passive microseismic monitoring of the hydraulic stimulation and circulation experiments has been used since 1982 to determine the size and structure of the reservoir, and monitor its growth. The active seismic survey techniques of cross-hole seismics and vertical seismic profiling (VSP) have been introduced to complement the passive microseismic monitoring in characterizing the reservoir. The cross-hole seismic surveys indicate that the microseismicity defines the area of joint dilation. The attenuation of high frequencies in the region of microseismicity suggests that the reservoir is composed of a complex zone of cracks rather than a single large fracture. VSP surveys also show a good agreement between the microseismically defined reservoir and seismic signal attenuation. Recent improvements in hardware, computer processing and interpretation indicate that active seismics will play an increasingly important part in mapping and understanding geothermal reservoirs. 11 figs., 10 refs.

Green, A.S.P.; Baria, R.

1987-01-20

17

Condensation Processes in Geothermal Systems  

Microsoft Academic Search

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

D. I. Norman; J. N. Moore

2005-01-01

18

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

19

Seismology and Enhanced Geothermal Systems  

Microsoft Academic Search

Recent technical advances increase the potential utility of seismological methods for monitoring physical processes in geothermal systems, and in Enhanced Geothermal Systems (EGS) experiments in particular, although many challenges remain. Differential methods for locating microearthquake hypocenters relative to one another can delineate the shapes of failure zones with a resolution of a few tens of meters, and the resulting images

B. R. Julian; G. R. Foulger

2010-01-01

20

Molybdenum mineralization in an active geothermal system, Valles caldera, New Mexico  

SciTech Connect

Shallow, sub-ore-grade molybdenite mineralization has been discovered in the active, high-temperature geothermal system penetrated by Continental Scientific Drilling Program corehole VC-2A at Sulfur Springs, in the western ring-fracture zone of the Valles caldera, New Mexico. This mineralization is hosted by fractured, quartz-sericitized, intracaldera ash-flow tuffs younger than 1.12 Ma. The molybdenite is an unusual, poorly crystalline variety that occurs in vuggy veinlets and breccia cements also containing quartz, sericite (illite), pyrite, and fluorite, as well as local sphalerite, rhodochrosite, and chalcopyrite. Fluid-inclusion data suggest that this assemblage was deposited from very dilute solutions at temperatures near 200/sup 0/C. Geochemical modeling indicates that under restricted pH and fO/sub 2/ conditions at 200/sup 0/C, the molybdenite and associated phases would be in equilibrium with hydrothermal fluids now circulating in the deep subsurface. The shallow molybdenite zone intersected in VC-2A may be the near-surface expression of deep, Climax-type stockwork molybdenum mineralization.

Hulen, J.B.; Nielson, D.L.; Goff, F.; Gardner, J.N.; Charles, R.W.

1987-08-01

21

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

22

Induced Microseismic Activity in non Pressure Stimulated Geothermal System - an Example From Southern Germany  

NASA Astrophysics Data System (ADS)

In order to be efficient in selling heat and electric power, the most favorable locations for deep geothermal power plants are in close proximity to urbanized areas. This advantage bears the inherent danger of induced earthquakes especially during the stimulation and production phase of enhanced geothermal systems, which at least are partially felt in the near surroundings. Felt earthquakes, however, severely reduce the level of acceptance of residents close to the plant. The Bavarian Molasse basin is characterized by its highly permeable, deep groundwater bearing limestone layers. This high permeability permits the abdication of pressure stimulation of the geothermal reservoir and makes the close proximity to the densely populated area around Munich possible. In addition to this favorable production conditions, the Bavarian Molasse Basin is being considered as generally aseismic. In contrast to this obvious advantages five Ml > 2.0 events south of Munich which were felt by local residents attracted public attention. These events were located in the 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 80 events with magnitudes mainly ranging from Ml -0.5 to 1.5. Events below magnitude 1.5 could not be detected and located prior to the production stage of the geothermal plant in the main network of the local earthquake service Erdbebendienst Bayern. Still, the exact mechanism leading to the seismicity remains unknown. Most likely the orientation of pre-existing faults, which are pierced by the open-hole part of wells with respect to present stress field and the volume of re-injected cold water play a key role in understanding the mechanisms leading to the observed seismicity. Within the framework of a project financed by the German federal ministry of Environment, further field experiments are conducted to address these open questions and test some working hypotheses. At two geothermal projects in comparable settings pre-production data is acquired in local seismometer networks to facilitate a comparison of possible microseismicity during production stages with natural background microseismicity.

Wassermann, J. M.; Megies, T.

2011-12-01

23

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

24

Geothermal activities in Central America  

SciTech Connect

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 self-contained logging truck will be made available for use throughout Central America. An important objective of this program is to involve the private sector in resource development. 4 refs., 3 figs.

Whetten, J.T.; Hanold, R.J.

1985-09-11

25

Computerized international geothermal information systems  

SciTech Connect

The computerized international geothermal energy information system is reviewed. The review covers establishment of the Italy - United States linked data centers by the NATO Committee on Challenges of Modern Society, through a bilateral agreement, and up to the present time. The result of the information exchange project is given as the bibliographic and numerical data available from the data centers. Recommendations for the exchange of computerized geothermal information at the international level are discussed.

Phillips, S.L.; Lawrence, J.D.; Lepman, S.R.

1980-03-01

26

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

27

A corrosivity classification system for geothermal resources  

SciTech Connect

The most important difference between traditional steam systems and those that utilize geothermal fluids is the potential for corrosion of metals. The recently developed sourcebook ''Materials Selection Guidelines for Geothermal Energy Utilization Systems'' is expected to facilitate corrosion engineering decision making and reduce the cost of geothermal systems where new resources are similar to those presented by the corrosivity classification system.

Conover, Marshall F.

1982-10-08

28

Geothermal systems: Principles and case histories  

Microsoft Academic Search

The classification of geothermal systems is considered along with the geophysical and geochemical signatures of geothermal systems, aspects of conductive heat transfer and regional heat flow, and geothermal anomalies and their plate tectonic framework. An investigation of convective heat and mass transfer in hydrothermal systems is conducted, taking into account the mathematical modelling of hydrothermal systems, aspects of idealized convective

L. Rybach; L. J. P. Muffler

1981-01-01

29

Mapping of faults activated by the stimulation of the Basel enhanced geothermal system  

NASA Astrophysics Data System (ADS)

High-precision relative location procedures of the stronger seismic events (0.7 < ML < 3.4), based on cross-correlations of signals recorded by a six-sensor borehole array and numerous surface stations in the immediate epicentral area, show that clustering of hypocenters on different spatial scales is a dominant feature of the microseismicity induced by the stimulation of enhanced geothermal reservoir in Basel. In line with the fact that many of the observed earthquakes form clusters of similar events, several focal mechanisms are also nearly identical to each other. A comparison between the high-precision relative locations of the events within each cluster and the focal mechanisms often shows a good coincidence of the hypocentral distribution with one of the nodal planes of the focal mechanism. In some cases, the spatial extent of the individual clusters is limited to a few meters, which suggests that the corresponding events represent repeated slip with partial stress drop as pore pressures increase with time. In other cases, that include some of the stronger events (ML > 2), the dimension of the individual clusters can amount to several 100 meters, and the activity within these clusters can extend over several days. Given that the orientation of many fault segments identified in this way deviates significantly from the overall orientation of the seismic cloud, these results reveal a complex internal structure of the flow paths in the rock volume stimulated by the water injection.

Deichmann, N.; Kraft, T.; Evans, K. F.

2012-04-01

30

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

31

Prediction of Scaling in Geothermal Systems  

Microsoft Academic Search

One of the main objectives of the DOE Geothermal Program is to improve the efficiency and reliability of geothermal operations so that this renewable form of energy can be integrated into the nation's energy system. Scale formation and other chemical problems associated with energy extraction from high temperature brines frequently inhibit the economical utilization of geothermal resources. In some cases,

John H. Weare; Nancy E. Moller

1989-01-01

32

The California Energy Commission's geothermal activities  

SciTech Connect

Thank you for the invitation to participate in this distinguished gathering. I would like to briefly relate the interests of the California Energy Commission in geothermal energy. Geothermal energy is a basic component of many of our primary activities, and is expressly cited in our statutory authority, the Warren-Alquist Act (1974). Our mandates affect the geothermal industry both directly and indirectly. The Commission is responsible for 5-, 12-, and 20-year forecasts of California electricity supply and demand. These forecasts are reported in our biennial Electricity Report. These forecasts are used in various official regulatory proceedings. The primary use is in the Commission's power plant siting authority. The forecasts establish the base used to determine the need for new capacity and energy in the current planning period. The forecasts are also used in other Commission activities as well as in proceedings at the Public Utilities Commission. The 1990 Electricity Report represents a dramatic change in the way this agency balances the relative importance of price competition, environmental quality, demand management as a system resource, and the implications of continued reliance on natural gas. Generally, the Commission is grappling with the elusive and complex problems of quantifying the appropriate value to assign to external (i. e., non-market) environmental attributes of competing technologies. While we have not decisively established such values, we do believe that they do exist and that we are moving in the right direction. The adopted policies have positive long term implications for geothermal and the other renewable technologies. The Commission has been in existence since 1975 and during that time has seen the development of geothermal energy in several areas of the state. As a regulatory agency, we have authority over the construction of thermal electric plants over 50 megawatts (MW). To date the Commission has certified the construction of more than 1200 MW in the Geysers. This area is now experiencing a dramatic loss in productivity. The Commission is engaged in a cooperative effort with the parties operating in the Geysers to address the problem of resource productivity. We held a hearing to examine the causes of the decline of the geothermal steam resources and its affect on electric energy supply. An outcome of the hearing was the establishment of a Technical Advisory Committee with the responsibility of providing the Commission projections of capacity and energy under the current rates of steam decline. The Committee was also charged with examining options on efficient resource management, including research and development, testing, and analyses regarding reservoir and power plant operations.

Crowley, Barbara

1991-01-01

33

The Iceland Deep Drilling Project (IDDP): (II) Isotopic Constraints on Ice Age Hydrothermal Fluids in Active High-Temperature Geothermal Systems  

NASA Astrophysics Data System (ADS)

The Krafla, Hengill and Reykjanes geothermal systems, located along the active rift-zone of Iceland, are three sites that will be drilled to 4-5 km depth by the Iceland Deep Drilling Project (IDDP). We use oxygen and hydrogen stable isotopes in hydrothermal minerals to characterize the source, composition and evolution of hydrothermal fluids in the IDDP geothermal systems. This research is essential to effectively characterizing geochemical and hydrologic processes occurring at depth within these regions, especially in the high latitudes of Iceland, where periods of glaciation can have long lasting impacts on geothermal environments. Recent studies of the stable isotope composition of hydrothermal epidote in the Reykjanes geothermal system indicate a complex history of fluid source and fluid-rock interaction since at least the Pleistocene. The chlorine concentration of modern Reykjanes geothermal fluids indicate that they are hydrothermally modified seawater. However, measured hydrogen isotope values of these fluids are as low as -23‰. ?D values of hydrothermal epidote analyzed from four wells in Reykjanes range from -60 to - 78‰. These values are not in isotopic equilibrium with present day geothermal fluids, and retain an isotopic signature of a glacially-dominated fluid source early in the evolution of the geothermal system. If the Reykjanes system was initially sub-glacial, the depth of boiling in the basalt would have been more shallow due to the overburden of a thick insulating ice sheet. This may explain the presence of epidote and garnet mineralization at levels as shallow as 500 m in some wells. Additionally, estimates of the water-rock ratio and modal abundance of hydrous alteration minerals in the system suggest that there is enough relict (Ice Age) hydrogen in hydrothermally altered basalt to diffusionally exchange with modern geothermal fluids and lower the fluid hydrogen isotope composition by as much as 20‰. This study shows that hydrogen isotopes of geothermal waters cannot be used independently to trace the origin of these fluids. The age of the geothermal system and the extent of alteration through water-rock interaction are also critical in determining the fluid source and isotope composition. In previous studies of the Krafla geothermal system, fluids had an average ?D value of -89‰, which closely reflect isotope values of local precipitation. However, geothermal fluids of the Nesjavellir system (near Hengill) are ~ -79‰, 10-20‰ lower than local meteoric water. Structural and hydrologic interpretations of the region make it unlikely that this difference is due to fluid flow from the nearby Langjökull ice sheet. Preliminary analyses of hydrothermal epidote in these systems (~ -125‰ in Krafla and -115‰ in Nesjavellir) suggest that they are in isotopic equilibrium with the hydrothermal fluids. Further analyses of mineral-mineral and mineral-fluid fractionation will help determine the relative input of nearby and distal modern meteoric fluids as well as the potential for relict glacially-derived fluids as a source for the observed values in both systems.

Pope, E. C.; Bird, D. K.; Arnórsson, S.; Fridriksson, T.; Elders, W. A.; Fridleifsson, G. Ø.

2008-12-01

34

Geothermal systems of northern Nevada  

USGS Publications Warehouse

Hot springs are numerous and nearly uniformly distributed in northern Nevada. Most occur on the flanks of basins, along Basin and Range (late Miocene to Holocene) faults, while some occur in the inner parts of the basins. Surface temperatures of the springs range from slightly above ambient to, boiling; some springs are superheated. Maximum subsurface water temperatures calculated on the basis of quartz solubility range as high as 252?C, although most are below 190?C. Flows range from a trickle to several hundred liters per minute. The Nevada geothermal systems differ markedly from the power-producing system at The Geysers, Calif., and from those areas with a high potential, for power production (e.g., Yellowstone Park, Wyo.; Jemez Mountains, N. Mex.). These other systems are associated with Quaternary felsic volcanic rocks and probably derive their heat from cooling magma rather high in the crust. In northern Nevada, however, felsic volcanic rocks are virtually all older than 10 million years, and. analogous magmatic heat sources are, therefore, probably lacking. Nevada is part of an area of much higher average heat flow than the rest of the United States. In north-central Nevada, geothermal gradients are as great as 64?C per kilometer in bedrock and even higher in basin fill. The high gradients probably result from a combination of thin crust and high temperature upper mantle. We suggest that the geothermal systems of northern Nevada result from circulation of meteoric waters along Basin and Range faults and that their temperature chiefly depends upon (1) depth of circulation and (2) the geothermal gradient near the faults.

Hose, Richard Kenneth; Taylor, Bruce Edward

1974-01-01

35

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

Microsoft Academic Search

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

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

2001-01-01

36

Gas Chemistry in Geothermal Systems  

SciTech Connect

Five new gas geothermometers are introduced. They are useful for predicting subsurface temperatures in water dominated geothermal systems. The geothermometers use data on CO{sub 2}, H{sub 2}S and H{sub 2} concentrations in fumarole steam as well as CO{sub 2}/H{sub 2} and H{sub 2}S/H{sub 2} ratios. It is demonstrated that the gas composition of fumarole steam may be used with or withour drillhole data to evaluate steam condensation in the upflow zones of geothermal systems. Uncertainty exists, however, in distinguishing between the effects of steam condensation and phase separation at elevated pressures. The gas content in steam from discharging wells and the solute content of the water phase can be used to evaluate which boiling processes lead to "excess steam" in the discharge and at which temperature this "excess steam" is added to the fluid moving through the aquifer and into the well. Examples, using field data, are given to demonstrate all the mentioned applications of geothermal chemistry.

Arnorsson, Stefan; Gunnlaugsson, Einar

1983-12-15

37

Geothermal pumping systems  

SciTech Connect

Improvements in electric submersible pumping systems have resulted in a demonstrated downhole running life of one year for low horsepower units operating in 180{sup 0}C brine. The implementation of a prototype pressurized lubrication system to prevent brine intrusion and loss of lubricating oil from the motor and protector sections has been successfully tested. Second generation pressurized lubrication systems have been designed and fabricated and will be utilized in downhole production pumping tests during FY 84. Pumping system lifetime is currently limited by available power cable designs that are degraded by high-temperature brine. A prototype metal-sheathed power cable has been designed and fabricated and is currently undergoing destructive and nondestructive laboratory testing. This cable design has the potential for eliminating brine intrusion into the power delivery system through the use of a hermetically sealed cable from the surface to the downhole motor.

Hanold, R.J.

1983-01-01

38

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

39

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

Microsoft Academic Search

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

Lynn McLarty; Daniel Entingh

2000-01-01

40

Recent geothermal reservoir engineering activities at Lawrence Berkeley Laboratory  

SciTech Connect

This paper briefly describes the most recent activities in reservoir engineering for the geothermal group of Lawrence Berkeley Laboratory (LBL). The primary emphasis of the geothermal program of LBL is dedicated to reservoir engineering including theoretical investigations, the development and application of mathematical models, and field studies. The objectives of these activities are to develop and validate methods and instruments which will be utilized in the determination of the parameters of geothermal systems, and the identification and evaluation of the importance of the distinct processes which occur in reservoirs. The ultimate goal of the program is the development of state of the art technologies which characterize geothermal reservoirs and evaluate their productive capacity and longevity.

Lippmann, M.J.; Bodvarsson, G.S.; Benson, S.M.; Pruess, K.

1987-09-01

41

Radon Measurements in Geothermal Systems.  

National Technical Information Service (NTIS)

This study is concerned with radon in geothermal reservoirs. Radon is a naturally occurring radioactive gas produced by the decay of radium. Radon release from geothermal reservoirs depends on the concentration and distribution of radium, the emanation pr...

A. K. Stoker P. Kruger

1975-01-01

42

Heat and helium in geothermal systems  

Microsoft Academic Search

The bulk of the Earth's heat budget and all of the 4 He is produced by natural uranium and thorium radioactivity, thus uniquely coupling heat and helium in geothermal systems. In the relatively simple geothermal systems associated with mid-ocean ridges, the helium isotopic composition and heat\\/ 3 He ratios are similar to the theoretically predicted values, confirming the coherence between

B. Mack Kennedy; T. P. Fischer; D. L. Shuster

2000-01-01

43

Induced Seismicity in Enhanced Geothermal Systems  

Microsoft Academic Search

The issue of induced seismicity in geothermal systems has become an issue in several geothermal fields over the last several years. Presented will be a case history at The Geysers, California on the rate and nature of seismicity as a fuction of injection and its impact on the management of the field and the surrounding community. The impact was both

E. L. Majer; J. E. Peterson

2006-01-01

44

Philip, South Dakota geothermal district heating systems  

SciTech Connect

The geothermal heating project in Philip, South Dakota which uses the waste water from the Haakon School has now been in operation for 15 years. This project was one of the 23 cost shared by the U.S. DOE starting in 1978, of which 15 became operational. This article describes the geothermal heating system for eight buildings in downtown Philip.

Lund, J.W.

1997-12-01

45

The Socorro Geothermal System: A Low Temperature Geothermal Resource  

NASA Astrophysics Data System (ADS)

The State of New Mexico is endowed with relatively high background heat flow and permeable, fractured crystalline and sedimentary rocks. This combination has given rise to numerous low temperature geothermal systems throughout the state. In many instances, hot springs associated with these systems are located within gaps in regional confining units (a.k.a. hydrologic windows) caused either by fault block rotation or the emplacement of volcanic dikes. The Socorro Geothermal Area (SGA) is a prime example of this type of a forced convection geothermal system. The Socorro geothermal area (SGA) lies 2 miles to the west of the NM Tech Campus near the base of the Socorro Mountain Block and will be assessed for production by drilling a 1500ft test well in September 2009. Published shallow temperature gradient measurements in fractured, permeable (3000 Darcy) granites indicate peak heat flow values as high as 490 mW/m^2 but decreases to 25 mW/m^2 about 10 km to the west within the La Jencia Basin near the foothills of the Magdalena Mountains. Silica and Cation based geothermometers suggest that deep geothermal reservoir reaches temperatures of 80 to 112 deg. C. Carbon14 age dating of shallow groundwater within the discharge area are about 20,000 years old. Hydrothermal models we constructed indicates that Mountain front recharge penetrates to depths of 4.5 km below the La Jencia Basin sedimentary pile into fractured, crystalline rocks. Discharge occurs through a hydrologic window to the east within a breached playa deposit at the western edge of the Socorro Basin. The hydrologic window was caused by fault block rotation. Warm springs which produce several hundred gpm of 32 deg. C water at the surface several miles to the south of the proposed drilling area also attest to the presence of a significant hydrothermal system. This low temperature resource could potentially heat the Campus of NM Tech.

Person, M. A.; Owens, L. B.

2009-12-01

46

Geopressured-geothermal well activities in Louisiana  

SciTech Connect

Since September 1978, microseismic networks have operated continuously around US Department of Energy (DOE) geopressured-geothermal well sites to monitor any microearthquake activity in the well vicinity. Microseismic monitoring is necessary before flow testing at a well site to establish the level of local background seismicity. Once flow testing has begun, well development may affect ground elevations and/or may activate growth faults, which are characteristic of the coastal region of southern Louisiana and southeastern Texas where these geopressured-geothermal wells are located. The microseismic networks are designed to detest small-scale local earthquakes indicative of such fault activation. Even after flow testing has ceased, monitoring continues to assess any microearthquake activity delayed by the time dependence of stress migration within the earth. Current monitoring shows no microseismicity in the geopressured-geothermal prospect areas before, during, or after flow testing.

John, C.J.

1992-10-01

47

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

48

Construction of the Geothermal Intelligent Management Information System  

Microsoft Academic Search

This paper described a new geothermal intelligent management information system for the development of geothermal resources with the character of geothermal development and exploitation. The geothermal intelligent management information system includes nine powering module such as the GIS(Geographic Information System) second development module, visual management module, communication module, the data transmission module, data statistics module, database module, alarm module, print

Tao Hu; Jialing Zhu; Wei Zhang

2012-01-01

49

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

Microsoft Academic Search

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

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

2009-01-01

50

Monitoring Biological Activity at Geothermal Power Plants  

Microsoft Academic Search

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,

Peter A. Pryfogle

2005-01-01

51

Geothermal hot water transportation and utilization system  

SciTech Connect

A geothermal hot water transportation system is described for transporting geothermal hot water from underground to above ground. The system consists of: means for pressurizing and pumping hot water from a geothermal production well to a location above ground including a downhole pump for installation in the geothermal production well, and a long downhole pump shaft; a pump casing having a below surface end connected to the downhole pump and an above surface end; means for separating steam and hot water brought to the surface from the well by the downhole pump through the pump casing, including an above ground rotary separation two-phase flow turbine communicating with the above surface end of the pump casing, the two-phase flow turbine having a power output shaft means for directly powering the downhole pump through the downhole pump shaft.

Yamaoka, K.

1986-03-18

52

Geothermal systems ancient and modern: a geochemical review  

Microsoft Academic Search

Geothermal systems occur in a range of crustal settings. The emphasis of this review is on those occurring in regions of active or recently active volcanism, where magmatic heat at depths up to 8 km leads to convection of groundwater in the upper crust. Hot water (and steam) flows are controlled by the permeability of the crust and recent data

R. W. Henley; A. J. Ellis

1983-01-01

53

Specific features of geothermal steam turbine control and emergency system  

Microsoft Academic Search

There are significant construction as well as operational differences between geothermal and conventional steam turbines. These result in specific features associated with geothermal steam turbine control and emergency system. Several aspects of geothermal steam turbine control have been considered. Some proposals of geothermal steam turbine control have been presented. Among others the following operation modes have been considered: Driving turbine,

Z. Domachowski; A. Gutierrez

1986-01-01

54

Evaluation of geothermal cooling systems for Arizona  

SciTech Connect

Arizona consumes nearly 50 percent more electricity during the peak summer season of May through part of October, due to the high cooling load met by electrical-driven air conditioning units. This study evaluates two geothermal-driven cooling systems that consume less electricity, namely, absorption cooling and heat pumps. Adsorption cooling requires a geothermal resource above 105{sup 0}C (220{sup 0}F) in order to operate at a reasonable efficiency and capacity. Geothermal resources at these temperatures or above are believed existing in the Phoenix and Tucson areas, but at such depths that geothermal-driven absorption systems have high capital investments. Such capital investments are uneconomical when paid out over only five months of operation each year, but become economical when cascaded with other geothermal uses. There may be other regions of the state, where geothermal resources exist at 105{sup 0}C (220{sup 0}F) or higher at much less depth, such as the Casa Grande/Coolidge or Hyder areas, which might be attractive locations for future plants of the high-technology industries. Geothermal assisted heat pumps have been shown in this study to be economical for nearly all areas of Arizona. They are more economical and reliable than air-to-air heat pumps. Such systems in Arizona depend upon a low-temperature geothermal resource in the narrow range of 15.5 to 26.6{sup 0}C (60 to 80{sup 0}F), and are widely available in Arizona. The state has over 3000 known (existing) thermal wells, out of a total of about 30,000 irrigation wells.

White, D.H.; Goldstone, L.A.

1982-08-01

55

An example of geothermal systems: Hidirlar Geothermal Field, Biga Peninsula, NW Turkey  

Microsoft Academic Search

Biga Peninsula located at northwestern Anatolia on southern segment on the dextral North Anatolian Fault and has many important geothermal potential areas. There are known 14 geothermal system namely Tuzla, Kestanbol, Hidirlar, Kirkgeçit, Kocabaslar, Bardakçilar, Palamutoba, Akçakeçili, Küçükçetmi, Külcüler, Tepeköy, Çan, Topaklar and Etili. Among them, an important field is the Hidirlar geothermal field, situated at the southeast of the

Özkan Ates; Salih Zeki Tutkun; Alper Baba; Heiko Woith; Süha Özden

2010-01-01

56

An example of geothermal systems: Hidirlar Geothermal Field, Biga Peninsula, NW Turkey  

NASA Astrophysics Data System (ADS)

Biga Peninsula located at northwestern Anatolia on southern segment on the dextral North Anatolian Fault and has many important geothermal potential areas. There are known 14 geothermal system namely Tuzla, Kestanbol, H?d?rlar, K?rkgeçit, Kocaba?lar, Bardakç?lar, Palamutoba, Akçakeçili, Küçükçetmi, Külcüler, Tepeköy, Çan, Topaklar and Etili. Among them, an important field is the H?d?rlar geothermal field, situated at the southeast of the Biga Peninsula. This field is in a tectonosedimentary basin and controlled by different trending faults. It has a potential usage about 87,7°C surface discharge temperature. Three thermal springs sampled in the H?d?rlar geothermal field. They have named as Spring, Drill and Uyuz. Their surface temperatures are Spring=77,5°C, Drill=57,7°C and Uyuz=53,6°C. According to the result of hydro-geochemical analysis and diagrams, thermal waters are generally Na-SO4 and Na-SO4-HCO3 water types. Assessments of chemical geothermometers applied to the thermal waters, suggest that reservoir temperatures are 90°C-163°C for Spring, 81°C-149°C for Drill and 83°C-161°C for Uyuz. Around H?d?rlar geothermal field, have been determined five different geological units. Lower-Middle Triassic aged Nilüfer Unit of Karakaya Complex is the basement unit. Late Oligocene aged Çak?roba granodiorite and Çan volcanic rocks overlie the basement metamorphic rocks with an unconformity. Neogene aged Örencik Formation, Quaternary aged slope washes and alluvium cover all older units with angular unconformity. Main structural trends have ENE-trending normal faults and they have been cutting by youngest NE-trending normal faults with a dextral strike-slip component. All thermal water springs are arranged on the NE-trending youngest faults. Both fault-slip data and joint measurements, mainly in granodiorites, show an active local extensional tectonic regime on southern segment of North Anatolian Fault. This local tectonic regime determined as the compressional (maximum stress axis, sigma 1) direction (N192±82°E) in center as vertical, NNE-trending extensional (minimum stress axis, sigma 3) direction (N21±23°E) and WNW-trending intermediate stress axis (sigma 2) direction (N114±9°E) in horizontal plane. Joints and faults which develop under these stress directions allow surface cold water's going underground. Depending to geothermic gradien these waters get warmer at the depth of crust and reach to surface again by these normal faults and joint system in H?d?rlar geothermal system. According to these results, this geothermal system can suggest for H?d?rlar geothermal field. Because of basement rocks exposure wide areas and around thermal water springs, metamorphic rocks cannot create a close system. Therefore these rocks don't have reservoir rock property. Granodiorites can be an important reservoir rock, because hot fluid can circulate inside and even get warmer. This geothermal field is fed by only meteoric water. Heater of this system is both geothermic gradient and granidiorites. Cap rock of this system can suggest as Neogene aged Örencik Formation.

Ate?, Özkan; Zeki Tutkun, Salih; Baba, Alper; Woith, Heiko; Özden, Süha

2010-05-01

57

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

58

Geothermal Progress Monitor. System status and operational experience  

SciTech Connect

The Geothermal Progress Monitor (GPM) system was designed and implemented by MITRE for DOE's Division of Geothermal Energy (now the Division of Geothermal and Hydropower Technologies). This report summarizes MITRE's operational experience with the system during fiscal year 1983 and provides a qualitative assessment of its data sources.

Gerstein, R.E.; Medville, D.M.

1983-11-01

59

Induced seismicity associated with Enhanced Geothermal Systems  

Microsoft Academic Search

Enhanced Geothermal Systems (EGS) have the potential to make a significant contribution to the world energy inventory. One controversial issue associated with EGS, however, is the impact of induced seismicity or microseismicity, which has been the cause of delays and threatened cancellation of at least two EGS projects worldwide. Although microseismicity has in fact had few (or no) adverse physical

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

2007-01-01

60

Induced seismicity associated with enhanced geothermal system  

Microsoft Academic Search

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

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

2006-01-01

61

COST OF ELECTRICITY FROM ENHANCED GEOTHERMAL SYSTEMS  

Microsoft Academic Search

This paper presents the results of an analysis of the cost of electric power from Enhanced Geothermal Systems (EGS), specifically, reservoirs with sub- commercial permeability enhanced by hydraulic stimulation. The parameters in this exercise reflect the conditions encountered at the Desert Peak EGS project in Nevada, but the results should be applicable, at least qualitatively, to any EGS project. Several

Subir K. Sanyal; James W. Morrow; Steven J. Butler

62

Tracers for Characterizing Enhanced Geothermal Systems  

Microsoft Academic Search

Information about the times of thermal breakthrough and subsequent rates of thermal drawdown in enhanced geothermal systems (EGS) is necessary for reservoir management, designing fracture stimulation and well drilling programs, and forecasting economic return. Thermal breakthrough in heterogeneous porous media can be estimated using conservative tracers and assumptions about heat transfer rates; however, tracers that undergo temperature-dependent changes can provide

Karen Wright; George Redden; Carl D. Palmer; Harry Rollins; Mark Stone; Mason Harrup; Laurence C. Hull

2010-01-01

63

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

64

Geothermal materials development: FY 1990 accomplishments and current activities  

SciTech Connect

Advances in the development of hydrothermally stable materials, the commercial availabilities of which are considered essential for the attainment of the Geothermal Division's (GD) Hydrothermal Category Objectives, continue to be made. Fiscal year 1990 R D was focused on reducing well drilling and completion costs, energy conversion costs, and on mitigating corrosion in well casing. Activities on lost circulation control materials, CO{sub 2}-resistant lightweight cements and thermally conductive corrosion and scale-resistant linear systems have reached the final development stages. In addition, field tests to determine the feasibility for the use of polymer cement liners to mitigate HCl-induced corrosion at the Geysers were performed. Technology transfer efforts on high temperature elastomers for use in drilling tools such as drillpipe protectors and rotating head seals were continued under Geothermal Drilling Organization sponsorship. Recent accomplishments and ongoing work on each of these activities are described in the paper. 8 refs.

Kukacka, L.E.

1991-01-01

65

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

66

Geothermal Resource Analysis and Structure of Basin and Range Systems, Especially Dixie Valley Geothermal Field, Nevada  

SciTech Connect

Publish new thermal and drill data from the Dizie Valley Geothermal Field that affect evaluation of Basin and Range Geothermal Resources in a very major and positive way. Completed new geophysical surveys of Dizie Valley including gravity and aeromagnetics and integrated the geophysical, seismic, geological and drilling data at Dizie Valley into local and regional geologic models. Developed natural state mass and energy transport fluid flow models of generic Basin and Range systems based on Dizie Valley data that help to understand the nature of large scale constraints on the location and characteristics of the geothermal systems. Documented a relation between natural heat loss for geothermal and electrical power production potential and determined heat flow for 27 different geothermal systems. Prepared data set for generation of a new geothermal map of North American including industry data totaling over 25,000 points in the US alone.

David Blackwell; Kenneth Wisian; Maria Richards; Mark Leidig; Richard Smith; Jason McKenna

2003-08-14

67

Geothermal Reservoir Dynamics TOUGHREACT.  

National Technical Information Service (NTIS)

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 (EG...

K. Pruess

2005-01-01

68

Utah State Prison Geothermal System  

SciTech Connect

A geothermal space heating project was recently completed at the Utah State Prison complex at Crystal Hot Springs located near Murray, Utah. The project was initiated in 1978 as a joint U.S. Department of Energy and State of Utah project. Geologic and geophysical investigations initiated in 1979 consist of surface geologic mapping and aeromagnetic and detailed gravity surveys. This exploration program along with several shallow thermal-gradient holes provided the structural details for a subsequent exploration drilling program. The exploration drilling program involved deepening an existing well (SF-1) to 500 ft (150 m) and drilling a new hole (USP/TH-1) to 1000 ft (300 m) to test the extent of the thermal anomaly. Well SF-1 intersected 175)2)F(79)2)C) temperatures in a low permeable quartzite, and well USP/TH-1 intersected highly fractured quartzite in the lower section of the well. A temperature reversal was noted in USP/TH-1 below 700 ft (213 m) with a maximum temperature of 175)2)F(79)2)C) occurring in the zone from 300 to 700 ft (90 to 215 m). Flow testing of USP/TH-1 indicated the well would flow at 1000 gpm with a sustained flow of 400 gpm at a 3.5 psi drawdown over the heating season. Testing also indicated interference with other nearby wells and thermal springs. Fluid production for space heating of the prison facilities took place during the winter of 1983-84. This production will give more data to refine the calculations of reservoir producibility and provide information on the economics of utilizing geothermal fluids for space heating.

Mink, L.R.

1984-07-01

69

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

Microsoft Academic Search

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

Günter Zimmermann; Guido Blöcher; Andreas Reinicke; Wulf Brandt

2011-01-01

70

Geothermal system meets space heating requirements  

SciTech Connect

The Department of Veterans Affairs (VA) Medical center was built on the site of the former Fort Boise. Ten of the 21 buildings that comprise the Medical Center are holdovers from the Fort Boise era, including the 1850s vintage boiler plant and plumbing shop, which previously served as the Idaho territorial jail. Historically, steam for heating, humidification, sterilization, cooking and other uses was generated in a central boiler plant and piped to the various buildings by an underground distribution network. In the early 1980s, the VA began planning to replace the boilers and parts of the piping network that had been in service for nearly 70 years. Because the Medical Center was located near a geothermal water source, it was decided to use the geothermal energy wherever possible. Drilling for the geothermal production well began in August 1983. Testing of the well indicated that it would yield a flow of 1,100 gpm (69 L/s) at 160{degrees}F (71{degrees}C). Engineering calculations indicated that this flow could accommodate all of the space heating and domestic hot water heating needs of the Medical Center. This paper reports that, because the geothermal water supply would consist of a single pump in a single well and because this was a healthcare facility, a backup heat system was required. The obvious choice was the existing boiler plant.

Not Available

1992-03-01

71

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

72

A spectral model for shallow geothermal systems  

Microsoft Academic Search

Purpose – The purpose of this paper is to introduce a spectral model capable of simulating fully transient conductive-convective heat transfer processes in an axially-symmetric shallow geothermal system consisting of a borehole heat exchanger embedded in a soil mass. Design\\/methodology\\/approach – The proposed model combines the exactness of the analytical methods with important extent of generality in describing the geometry

Rafid Al-Khoury

2012-01-01

73

Prediction of Scaling in Geothermal Systems  

SciTech Connect

One of the main objectives of the DOE Geothermal Program is to improve the efficiency and reliability of geothermal operations so that this renewable form of energy can be integrated into the nation's energy system. Scale formation and other chemical problems associated with energy extraction from high temperature brines frequently inhibit the economical utilization of geothermal resources. In some cases, these chemical problems can be so severe that development of a site must be abandoned after considerable capital investment. The goal of our research efforts is to construct an accurate computer model for describing the chemical behavior of geothermal brines under a wide range of operating conditions. This technology will provide industry a cost-effective means of identifying scaling problems in production and reinjection wells as well as in surface equipment, and also devising and testing methods for well as other uses described in table (1) can contribute significantly to meeting the objectives of the Geothermal Program. The chemical model we have developed to date can simulate calcium carbonate scale formation and gas solubilities in concentrated brines containing sodium, potassium, calcium, chloride and sulfate ions as a function of temperature to 250 C and for variable partial pressure of CO{sub 2}. It can predict the solubility of other scale-forming minerals, such as amorphous silica, gypsum-anhydrite, halite and glasserite, as a function of brine composition to 250 C. The only required input for the model is the temperature, pressure and composition of the brine. Our modeling approach is based on semi-empirical thermodynamic descriptions of aqueous solutions. The model equations are parameterized by careful comparison to a variety of laboratory data. The ability of the resulting models to accurately predict the chemical behavior of even very concentrated high temperature brines is well demonstrated. This ability is an unusual feature of our models which is vital for applications to many important geothermal systems, such as those found in the Imperial Valley of California. In this report, the use of the present version of our model will be illustrated by an application to the prediction of the onset of two phase flow (breakout) in a brine confined by an external pressure. Calculations of this kind are important in assessing the production potential of a geothermal resource because the initiation of breakout in a well bore or power plant is usually simultaneous with the appearance of massive scale deposition. It is therefore necessary to predict breakout and also to assess the consequences of breakout in designing more efficient energy extraction processes. For the geothermal brine for which we have reliable composition and breakout data (East Mesa in California), the model gives results which are essentially identical to the measured values. Calculations also illustrate the importance of contributions of dissolved gases to the total pressure of the brines. Applications to other scale formation problems in Dixie Valley geothermal brines will also be discussed.

Weare, John H.; Moller, Nancy E.

1989-03-21

74

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

75

Reconstruction of a pavement geothermal deicing system  

SciTech Connect

In 1948, US 97 in Klamath Falls, Oregon was routed over Esplanade Street to Main Street and through the downtown area. In order to widen the bridge across the US Bureau of Reclamation A Canal and to have the road cross under the Southern Pacific Railroad main north-south line, a new bridge and roadway were constructed at the beginning of this urban route. Because the approach and stop where this roadway intersected Alameda Ave (now Hwy 50 -- Eastside Bypass) caused problems with traffic getting traction in the winter on an adverse 8% grade, a geothermal experiment in pavement de-icing was incorporated into the project. A grid system within the pavement was connected to a nearby geothermal well using a downhole heat exchanger (DHE). The 419-foot well provided heat to a 50-50 ethylene glycol-water solution that ran through the grid system at about 50 gpm. This energy could provide a relatively snow free pavement at an outside temperature of {minus}10 F and snowfall up to 3 inches per hour, at a heat requirement of 41 Btu/hr/ft{sup 2}. Over time, the well temperature dropped from 143 to 98 F at the surface. The bridge and surface pavement, geothermal well, and associated equipment were modified. This paper describes the modifications.

Lund, J.W. [Geo-Heat Center, Klamath Falls, OR (United States)

1999-03-01

76

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

77

Numerical models for the evaluation of geothermal systems  

SciTech Connect

We have carried out detailed simulations of various fields in the USA (Bada, New Mexico; Heber, California); Mexico (Cerro Prieto); Iceland (Krafla); and Kenya (Olkaria). These simulation studies have illustrated the usefulness of numerical models for the overall evaluation of geothermal systems. The methodology for modeling the behavior of geothermal systems, different approaches to geothermal reservoir modeling and how they can be applied in comprehensive evaluation work are discussed.

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

1986-08-01

78

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

79

Conceptual design of a geothermal site development forecasting system  

SciTech Connect

A site development forecasting system has been designed in response to the need to monitor and forecast the development of specific geothermal resource sites for electrical power generation and direct heat applications. The system is comprised of customized software, a site development status data base, and a set of complex geothermal project development schedules. The system would use site-specific development status information obtained from the Geothermal Progress Monitor and other data derived from economic and market penetration studies to produce reports on the rates of geothermal energy development, federal agency manpower requirements to ensure these developments, and capital expenditures and technical/laborer manpower required to achieve these developments.

Neham, E.A.; Entingh, D.J.

1980-03-01

80

Geothermal energy control system and method  

DOEpatents

A geothermal energy transfer and utilization system makes use of thermal energy stored in hot solute-bearing well water to generate super-heated steam from an injected flow of clean water; the super-heated steam is then used for operating a turbine-driven pump at the well bottom for pumping the hot solute-bearing water at high pressure and in liquid state to the earth's surface, where it is used by transfer of its heat to a closed-loop boiler-turbine-alternator combination for the generation of electrical or other power. Residual concentrated solute-bearing water is pumped back into the earth. The clean cooled water is regenerated at the surface-located system and is returned to the deep well pumping system also for lubrication of a novel bearing arrangement supporting the turbine-driven pump system. The bearing system employs liquid lubricated thrust and radial bearings with all bearing surfaces bathed in clean water serving as a lubricant and maintained under pressure to prevent entry into the bearings of contaminated geothermal fluid, an auxiliary thrust ball bearing arrangement comes into operation when starting or stopping the pumping system.

Matthews, Hugh B. (Acton, MA)

1977-01-01

81

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

82

Hydrothermal model of the Momotombo geothermal system, Nicaragua  

SciTech Connect

The Momotombo geotherinal field is situated on the northern shore of Lake Managua at the foot of the active Momotombo volcano. The field has been producing electricity since 1983 and has an installed capacity of 70 MWe. The results of geological, geochemical and geophysical studies have been reported in various internal reports. The isotopic studies were funded by the International Atomic Energy Agency (IAEA), Vienna to develop a hydrothermal model of the geothermal system. The chemical and stable isotopic data (?18O and ?D) of the geothermal fluid suggest that the seasonal variation in the production characteristics of the wells is related to the rapid infiltration of local precipitation into the reservoir. The annual average composition of Na+, K+ and Mg2+ plotted on the Na- K-Mg triangular diagram presented by Giggenbach (1988) to identify the state of rock-water interaction in geothermal reservoirs, shows that the fluids of almost every well are shifting towards chemically immature water due to resenroir exploitation. This effect is prominent in wells Mt-2. Mt-12, Mt-22 and Mt-27. The local groundwaters including surface water from Lake Managua have much lower tritium concentrations than sonic of the geothermal well fluids, which have about 6 T.U. The high-tritium wells are located along a fault inferred froin a thermal anomaly. The tritium concentration is also higher in fluids from wells close to the lake. This could indicate that older local precipitation waters are stored in a deep layer within the lake and that they are infiltrating into the geothermal reservoir.

Verma, M.P.; Martinez, E.; Sanchez, M.; Miranda, K.; Gerardo, J.Y.; Araguas, L.

1996-01-24

83

Modeling of Flow And Transport in Enhanced Geothermal Systems (Invited)  

Microsoft Academic Search

Here, we consider Enhanced Geothermal Systems (EGS), which rely on increased permeability and artificially created fracture networks in the subsurface, thus increasing the efficiency of geothermal power plants. By injecting cold supercritical working fluid (usually H2O or CO2) into the ``damaged matrix'', new fractures are created. This dynamically changing fracture system allows the working fluid to flow efficiently through the

D. Karvounis; P. Jenny

2010-01-01

84

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

85

Quantitative Risk Assessment for Enhanced Geothermal Systems  

NASA Astrophysics Data System (ADS)

This study uses a quantitative risk-assessment approach to place the uncertainty associated with enhanced geothermal systems (EGS) development into meaningful context and to identify points of attack that can reduce risk the most. Using the integrated geothermal assessment tool, GT-Mod, we calculate the complimentary cumulative distribution function of the levelized cost of electricity (LCOE) that results from uncertainty in a variety of geologic and economic input parameter values. EGS is a developing technology that taps deep (2-10km) geologic heat sources for energy production by "enhancing" non-permeable hot rock through hydraulic stimulation. Despite the promise of EGS, uncertainties in predicting the physical end economic performance of a site has hindered its development. To address this, we apply a quantitative risk-assessment approach that calculates risk as the sum of the consequence, C, multiplied by the range of the probability, ?P, over all estimations of a given exceedance probability, n, over time, t. The consequence here is defined as the deviation from the best estimate LCOE, which is calculated using the 'best-guess' input parameter values. The analysis assumes a realistic but fictitious EGS site with uncertainties in the exploration success rate, the sub-surface thermal gradient, the reservoir fracture pattern, and the power plant performance. Uncertainty in the exploration, construction, O&M, and drilling costs are also included. The depth to the resource is calculated from the thermal gradient and a target resource temperature of 225 °C. Thermal performance is simulated using the Gringarten analytical solution. The mass flow rate is set to produce 30 MWe of power for the given conditions and is adjusted over time to maintain that rate over the plant lifetime of 30 years. Simulations are conducted using GT-Mod, which dynamically links the physical systems of a geothermal site to simulate, as an integrated, multi-system component, the collective performance of each system over time. It is dynamically linked to the Geothermal Energy Technology Evaluation Model (GETEM - www1.eere.energy.gov/geothermal/getem.html) that calculates the LCOE based on time-series performance output from GT-Mod. A Monte Carlo approach propagates input uncertainties to the output by describing uncertain inputs with probability density functions (PDF's) and then simultaneously varying the PDF's via a Latin Hypercube Sampling (LHS) technique. Exceedance probabilities for the LCOE are calculated as a post-processing exercise. Results show that for the given set of uncertainties, the LCOE assumes a lognormal distribution with the tail skewed towards the higher values and a mean LCOE that is almost 2 ¢/kWh higher than the best estimate; this despite the fact that the 'best-guess' parameter values are the mean values of the input PDF's. This is a result of component feedback that can amplify the system's dynamics and implies that the best estimate LCOE may considerably under-estimate the risk of developing that site. Correlation analysis indicates that reductions in drilling costs and better characterization of the sub-surface environment will reduce risk the most.

Lowry, T. S.; McKenna, S. A.; Hadgu, T.; Kalinina, E.

2011-12-01

86

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

87

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

Microsoft Academic Search

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

Dan Entingh; Lynn McLarty

2000-01-01

88

Seismic Velocity Structures of Larderello Geothermal System, Italy: Preliminary Results  

Microsoft Academic Search

The steam-dominated geothermal system of Larderello is located in Tuscany and is the largest Italian area of electricity generation from geothermal resources. Enel Green Power, the main company of the ENEL Group involved in the renewable resources development, has drilled several wells down to maximum depth of about 4.0 km below see level in order to exploit deep and hot

R. de Matteis; T. Vanorio; B. Ciulli; E. Spinelli; A. Fiordelisi; A. Zollo

2002-01-01

89

Outstanding Issues in the Assessment of Enhanced Geothermal Systems Resources  

Microsoft Academic Search

The successful implementation of Enhanced Geothermal Systems (EGS) technology has the potential to dramatically expand both the magnitude and spatial extent of geothermal energy production, and the U.S. Geological Survey (USGS) has been working to develop a comprehensive EGS resource assessment for the United States. However, a number of outstanding scientific and technical issues must be resolved in order to

C. Williams; J. Deangelo

2010-01-01

90

Enhanced Geothermal Systems: Mitigating Risk in Urban Areas  

Microsoft Academic Search

With the global challenge to satisfy an increasing demand for energy while at the same time stabilizing or reducing carbon dioxide (CO2) concentrations in the atmosphere, geothermal energy from enhanced geothermal systems (EGSs) increasingly is being recognized as an attractive alternative energy source throughout the world. However, the risks associated with the seismicity necessarily induced during the development of an

Toni Kraft; Paul Martin Mai; Stefan Wiemer; Nicholas Deichmann; Johannes Ripperger; Philipp Kästli; Corinne Bachmann; Donat Fäh; Jochen Wössner; Domenico Giardini

2009-01-01

91

NUMERICAL SIMULATION OF EXPLOITATION OF SUPERCRITICAL ENHANCED GEOTHERMAL SYSTEM  

Microsoft Academic Search

S The process of heat transfer during the fluid filtration in rocks of magma-geothermal system of Mutnovsky volcano was studied by the method of numerical simulation. The distribution of temperature, pressure, fluid phase state and its phases' velocities were obtained. The character of dependence of the calculated geothermal gradient and geometry of supercritical fluid region on the form of magma

Roman I. Pashkevich; Vitaly V. Taskin

92

Enhanced Geothermal Systems (EGS) R&D Program  

Microsoft Academic Search

The purpose of this workshop was to develop technical background facts necessary for planning continued research and development of Enhanced Geothermal Systems (EGS). EGS are geothermal reservoirs that require improvement of their permeability or fluid contents in order to achieve economic energy production. The initial focus of this R&D program is devising and testing means to extract additional economic energy

Entingh; Daniel J

1999-01-01

93

Active and passive seismic studies of geothermal resources in New Mexico and investigations of earthquake hazards to geothermal development  

SciTech Connect

Seismic data were collected in southwestern New Mexico to investigate the sources of the geothermal anomalies and to investigate the potential earthquake hazards of geothermal development. No major crustal structure anomalies have been located related to known geothermal resources, and no areas of continual seismicity have been identified, which is interpreted to indicate a lack of active, or recently active crustal intrusions in southwestern New Mexico. Without a magnetic heat source, the geothermal potential of the known anomalies is probably limited to intermediate and low temperature applications (<180/sup 0/C). The lack of continual seismicity indicates low seismic hazard in the area directly related to geothermal development, although the historic and geologically recent tectonic activity should be taken into consideration during any development in the area. A model of forced groundwater convection is presented to explain the geothermal anomalies in southwestern New Mexico, which is consistent with all available geological and geophysical data from the area.

Morgan, P.; Daggett, P.H.

1980-01-01

94

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

95

Geothermal systems in Iceland: Structure and conceptual models—I. High-temperature areas  

Microsoft Academic Search

There are 20 known high-temperature geothermal areas in Iceland and another eight potential areas. Surface manifestations are meagre in these eight areas and not conclusive, and no drilling has been carried out to prove or disprove the existence of high-temperature geothermal systems at depth. The high-temperature areas are located within the active volcanic belts or marginal to them. The heat

Stefán Arnórsson

1995-01-01

96

Active and Fossil Geothermal Activity at Lake Chapala, Mexico  

NASA Astrophysics Data System (ADS)

Geothermal systems are very abundant in the tectonically active zones of the earth's crust and the Citala rift, where Lake Chapala is located, is not the exception. The Lake Chapala basin is characterized by its paleo- and actual geothermal activity that includes: thermal springs, fossil sinter deposits and hydrothermal petroleum manifestations. Thermal springs occur both inside and outside the lake. The spring water in out-shore thermal springs around Lake Chapala is carbonate (Medina-Heredia A, 1986). To the NE area is San Luis Agua Caliente (69°C; ~ 240 mg L-1 [HCO3]1) in the NW at Jocotepec (36°C; ~263mg L-1 [HCO3]-); in the South we find Tuxcueca and Tizap n El Alto (30°C; 193 mg L-1 [HCO3]-). However, there is an exception, the spring water at the San Juan Cosal sector (North), which is sulfate (64-83°C; ~479 mg L-1, [SO4]-2). Examples of in-shore thermal springs are "Los Gorgos" (near South shore) and "El Fuerte" (near East shore and temporary "out-shore" because of actual severe drought); the characterisation of water of this in-shore sites is in progress. On the SE shore and five km NW from Regules village, outcrops a carbonate deposit named "La Calera". This carbonate fossil sinter outcrops 2 km in E-W direction and 600 m in N-S direction and overlays andesitic rock. With a thickness of approximately 5m and a roughly horizontal attitude, the carbonated sinter material is characterized by both massive and banded structure. When massive, it is colored in yellow brownish and grey and elsewhere it shows a pseudo-brecciated structure and when banded, alternated of yellow and dark millimetre bands can be seen; is characterized by vuggy porosity and silica (quartz and chalcedony) vein lets. Under microscope a pseudo-micritic texture is observed; vugs coated by iron oxides, are filled with calcite, and/or quartz, chalcedony and clay minerals. Six samples of carbonate of "La Calera" deposit were analysed for their stable isotopes (LODC-UParis VI). From ? 13CPDB values we have two set of data: one near zero (-8.03 to -8.69 \\permil) that means a no contribution of organic carbon and other with low values (-0.35 to -0.75 \\permil) meaning an important contribution of organic carbon; from very low ? 18OPDB values (-8.5 to -0.27 \\permil) we deduced a precipitation in meteoric water with a temperature deposition higher than the surface that matchs with an hydrothermal origin. Mineralogy was confirmed by XRD diffractometry. Near the sub-lacustrine spring "Los Gorgos" there are some small land spots which look like islands (<3-4 m2) made of solid bitumen and which are linked to the bottom of the lake. Because of these hydrocarbon manifestations the company Petróleos Mexicanos drilled (2,348 m deep), without success, an oil exploration well (L¢pez-Ramos, 1979). The characterisation of this solid bitumen is in progress.

Zârate-del Vall, P.

2002-12-01

97

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

98

Heat pump assisted geothermal heating system for Felix Spa, Romania  

SciTech Connect

The paper presents a pre-feasibility type study of a proposed heat pump assisted geothermal heating system for an average hotel in Felix Spa, Romania. After a brief presentation of the geothermal reservoir, the paper gives the methodology and the results of the technical and economical calculations. The technical and economical viability of the proposed system is discussed in detail in the final part of the paper.

Rosca, Marcel; Maghiar, Teodor

1996-01-24

99

Magnetotelluric imaging of the Reporoa geothermal system in New Zealand  

NASA Astrophysics Data System (ADS)

The Reporoa geothermal area is located in a caldera on the eastern side of the Taupo Volcanic Zone in the North Island of New Zealand. For the last 40 years scientists have argued whether Reporoa is an independent geothermal system or just an outflow structure of the Waiotapu geothermal system to the north. Due to its location and possible connection to the Waiotapu geothermal system, which is a protected system and a big tourist attraction, the Reporoa system needs to be well characterised before commercial exploitation can be considered. Early DC resistivity surveys yielded information to depths of about 1 km, but were unable to resolve which, if either, of the two competing models was correct. In this project we electrically image much deeper structures beneath the Reporoa geothermal area in order to understand better this system. MT is a passive geophysical exploration tool that utilises naturally-occurring, time-varying electromagnetic (EM) fields recorded on the surface to determine spatial variations in subsurface electrical resistivity. Temperature, porosity and fluid content, as well as hydrothermal alteration processes, have significant effects on patterns of subsurface electrical resistivity. Therefore, MT is well suited to image the different parts of a geothermal system, and is accordingly the most utilized geophysical imaging technique in geothermal research. For this study close to 100 broadband Magnetotelluric (MT) measurements, acquired during several separate surveys over a 3 year period, were analysed and modelled. Station spacing varied from 500 m to 2 km forming a grid over the study area. The maximum depth of investigation for this study, which is a function of the subsurface resistivity and the maximum period of measurement (100 s), is of the order of several kilometres. This paper will describe the data acquired and models derived. Preliminary results from this study indicate both an outflow structure from Waiotapu at shallow depths and an independent geothermal upflow at depth.

Walter, Christina; Jones, Alan G.; Ryan, Graham A.

2013-04-01

100

A problem posed by vapour-dominated geothermal systems  

NASA Astrophysics Data System (ADS)

Vapor-dominated geothermal systems present an apparently extraordinary physical phenomenon - a layer of water lying stably on a body of steam. The first geothermal exploitation at Lardarello, Italy, was in such an area. An analysis of the gravitational stability of water over steam in a porous medium is presented here. This shows that the near-surface condensate layer of a vapor-dominated geothermal system can be stably maintained above the main steam reservoir by restoring forces associated with the displacement of the phase-change interface. For typical conditions in vapor-dominated geothermal systems, stability can be maintained provided that the permeability of the rocks at the depth of the steam-water boundary does not exceed about 40 sq nm (0.04 millidarcy). The stability requirement determines the thickness of the condensate layer or the proximity of the top of the steam reservoir to the surface.

Schubert, G.; Straus, J. M.; Grant, M. A.

1980-10-01

101

Low-Temperature Geothermal Systems and Groundwater Protection  

NASA Astrophysics Data System (ADS)

The development of low temperature geothermal systems for space heating or cooling residential, institutional, commercial and industrial buildings has been steadily increasing in Canada and nations world-wide, primarily due to the associated environmental and cost benefits. Although geothermal systems are generally regarded as a 'green' and 'sustainable' energy source, recent studies have highlighted that the migration of thermal anomalies associated with these subsurface systems can result in adverse impacts to environmental receptors and these systems should be a consideration in groundwater protection. This is particularly true where groundwater is important in the regulation of surface water temperatures and where temperature dependent reactions might affect groundwater quality. In this study, environmental implications of geothermal systems will be evaluated by monitoring groundwater temperatures in wells surrounding existing geothermal developments in different geophysical areas of Nova Scotia. The collected data, in conjunction with existing data, will be used to create numerical models capable of predicting the nature and extent of thermal changes caused by the long-term operation of a geothermal system. Observations and model results will be used to assist in the creation of guidelines to develop geothermal resources in an optimal and sustainable manner for both the thermal application and the environment.

Watters, K.; Ferguson, G.

2009-05-01

102

Fluid flow processes in the Beppu geothermal system, Japan  

SciTech Connect

This paper reports on the Beppu geothermal system, centered beneath the late Quaternary volcanoes of Tsurumi and Garandake at the northern end of the Ryukyu volcanic arc. The deep fluid has a temperature of at least 250--300{degrees} C, and an inferred chloride concentration of 1400--1600 mg/kg. Apart from fumarolic areas near the summits of the two volcanoes, most thermal activity occurs at low elevation along the two main outflow paths towards the coast. The hot spring waters of downtown Beppu have originated from outflow along the Asamigawa Fault, with their chemistry indicating predominantly dilution of the deep fluid by groundwater. The second outflow zone towards the hot spring area of downtown Kamegawa coincides with a ridge of lavas. Here boiling, steam loss, and subsequent mixing with steam-heated groundwaters have significantly modified both the deep fluid and host rocks. The area of the geothermal system above 200{degrees} C is at least 15 km{sup 2} at sea level, and the total natural heat output is inferred to be at least 250 MW. Most of this heat output occurs as subsurface hot water outflows towards the coast due to the 1300 m of topographic relief across the system.

Allis, R.G. (Geophysics Div., Geothermal Reserarch Center, Private Bag, Taupo (NZ)); Yusa, Y. (Beppu Geophysical Research Lab., Kyoto Univ., Beppu 874 (JP))

1989-01-01

103

LIFE CYCLE MODELING OF WELLBORE CEMENT SYSTEMS USED FOR ENHANCED GEOTHERMAL SYSTEM DEVELOPMENT  

Microsoft Academic Search

Coso Operating Company, LLC (COC), and the Energy and Geosciences Institute (EGI) at the University of Utah have been granted funding from the Department of Energy to develop an enhanced geothermal system (EGS) at Coso. Coso is an operating geothermal plant that will provide an excellent opportunity to experiment with methods for enhancing the geothermal reservoir through hydraulic, thermal, and

Susan Petty; John Gastineau; Daniel L. Bour; Kris Ravi

104

Design Considerations for Artificial Lifting of Enhanced Geothermal System Fluids  

SciTech Connect

This work evaluates the effect of production well pumping requirements on power generation. The amount of work that can be extracted from a geothermal fluid and the rate at which this work is converted to power increase as the reservoir temperature increases. Artificial lifting is an important issue in this process. The results presented are based on a configuration comprising one production well and one injection well, representing an enhanced geothermal system. The effects of the hydraulic conductivity of the geothermal reservoir, the flow rate, and the size of the production casing are considered in the study. Besides submersible pumps, the possibility of using lineshaft pumps is also discussed.

Xina Xie; K. K. Bloomfield; G. L. Mines; G. M. Shook

2005-07-01

105

Energy Analysis of Geothermal-Electric Systems.  

National Technical Information Service (NTIS)

Standard energy analysis was applied to 4 types of geothermal-electric technologies: liquid dominated, hot dry rock, geopressure, and vapor dominated. It was found that all are net energy producers. Expected uncertainties are not large enough to threaten ...

R. Plant R. A. Herendeen

1979-01-01

106

Seismic signals in geothermal areas of active volcanism: a case study from ‘La Fossa’, Vulcano (Italy)  

Microsoft Academic Search

Since the last eruption (1888–1890) volcanism at Vulcano, Aeolian Archipelago, southern Tyrrhenian Sea, has taken the form of persistent fumarolic activity. The gas-vapour phases of the geothermal systems are mainly discharged within two restricted areas about 1 km apart from each other, in the northern part of the island. These areas are ‘La Fossa’ crater, and the beach fumaroles of

Antonio Montalto

1994-01-01

107

Monitoring well systems in geothermal areas  

SciTech Connect

The ability to monitor the injection of spent geothermal fluids at reasonable cost might be greatly improved by use of multiple-completion techniques. Several such techniques, identified through contact with a broad range of experts from the groundwater and petroleum industries, are evaluated relative to application in the typical geologic and hydrologic conditions of the Basin and Range Province of the Western United States. Three basic monitor well designs are suggested for collection of pressure and temperature data: Single standpipe, multiple standpipe, and closed-system piezometers. A fourth design, monitor well/injection well dual completions, is determined to be inadvisable. Also, while it is recognized that water quality data is equally important, designs to allow water sampling greatly increase costs of construction, and so such designs are not included in this review. The single standpipe piezometer is recommended for use at depths less than 152 m (500 ft); several can be clustered in one area to provide information on vertical flow conditions. At depths greater than 152 m (500 ft), the multiple-completion standpipe and closed-system piezometers are likely to be more cost effective. Unique conditions at each monitor well site may necessitate consideration of the single standpipe piezometer even for deeper completions.

Lofgren, B.E.; O'Rourke, J.; Sterrett, R.; Thackston, J.; Fain, D.

1982-03-01

108

Geothermal Today.  

National Technical Information Service (NTIS)

This outreach publication highlights milestones and accomplishments of the DOE Geothermal Technologies Program for 2002. Included in this publication are discussions of geothermal fundamentals, enhanced geothermal systems, direct-use applications, geother...

2003-01-01

109

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

110

Early Devonian geothermal systems in northeast Scotland: Exploration targets for epithermal gold  

Microsoft Academic Search

Early Devonian geothermal activity is recognized in northeast Scotland by the remnants of silica sinter, a hot-spring manganese deposit, an area of steam alteration, and hydrothermal eruption breccias. At least five systems were active at this time, three of which are located on or near the intersection of major faults and lineaments. Two deposits can be dated as Early Devonian,

Keith Nicholson

1989-01-01

111

High Potential Regions for Enhanced Geothermal Systems in Canada  

Microsoft Academic Search

Previous estimates of geothermal energy potential in Canada give an indication of available heat to be ‘farmed’ at depth.\\u000a This article examines in more detail depth–temperature relationships near large population centers in western Canada, as well\\u000a as remote communities in northern Canada, in order to provide a first order assessment of Enhanced Geothermal Systems (EGS)\\u000a potential for electrical generation. Quantities

Jacek Majorowicz; Stephen E. Grasby

2010-01-01

112

Enhanced Geothermal Systems (EGS) R&D Program  

SciTech Connect

The purpose of this workshop was to develop technical background facts necessary for planning continued research and development of Enhanced Geothermal Systems (EGS). EGS are geothermal reservoirs that require improvement of their permeability or fluid contents in order to achieve economic energy production. The initial focus of this R&D program is devising and testing means to extract additional economic energy from marginal volumes of hydrothermal reservoirs that are already producing commercial energy. By mid-1999, the evolution of the EGS R&D Program, begun in FY 1988 by the U.S. Department of Energy (DOE), reached the stage where considerable expertise had to be brought to bear on what technical goals should be pursued. The main purpose of this Workshop was to do that. The Workshop was sponsored by the Office of Geothermal Technologies of the Department of Energy. Its purpose and timing were endorsed by the EGS National Coordinating Committee, through which the EGS R&D Program receives guidance from members of the U.S. geothermal industry. Section 1.0 of this report documents the EGS R&D Program Review Session. There, managers and researchers described the goals and activities of the program. Recent experience with injection at The Geysers and analysis of downhole conditions at Dixie Valley highlighted this session. Section 2.0 contains a number of technical presentations that were invited or volunteered to illuminate important technical and economic facts and opportunities for research. The emphasis here was on fi.acture creation, detection, and analysis. Section 3.0 documents the initial general discussions of the participants. Important topics that emerged were: Specificity of defined projects, Optimizing cost effectiveness, Main technical areas to work on, Overlaps between EGS and Reservoir Technology R&D areas, Relationship of microseismic events to hydraulic fractures, and Defining criteria for prioritizing research thrusts. Sections 4.0 and 5.0 report the meat of the Workshop. Section 4.0 describes the nomination and clarification of technical thrusts, and Section 5.0 reports the results of prioritizing those thrusts via voting by the participants. Section 6.0 contains two discussions conducted after the work on research thrusts. The topics were ''Simulation'' and ''Stimulation''. A number of technical points that emerged here provide important guidance for both practical field work on EGS systems and for research.

Entingh, Daniel J.

1999-08-18

113

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

114

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

115

Removal of carbon dioxide in geothermal power systems  

SciTech Connect

A process for removing carbon dioxide in geothermal power generating processes employing a geothermal fluid such as geothermal brine containing carbon dioxide, to improve the efficiency of geothermal power generation, comprises introducing an aqueous alkaline solution, preferably an aqueous calcium hydroxide solution, into a vapor stream obtained from the brine during power generation, to remove carbon dioxide from the stream. In the case, for example, of power generation by direct contact heat exchange between geothermal brine and a working fluid such as isobutane, where the working fluid is expanded to generate power, aqueous calcium hydroxide can be introduced into a direct contact condenser into contact with the working fluid therein to remove CO2 present in the working fluid, thereby aiding in reducing loss of working fluid from the system and aiding in reducing pump power. The aqueous alkaline, E.G., calcium hydroxide, solution alternatively can be contacted with the geothermal fluid prior to flashing or prior to direct contact heat exchange with a working fluid, to remove CO2 from uncondensible gas contained in the fluid.

Wahl, E.F.

1982-11-09

116

[Geothermal system temperature-depth database and model for data analysis]. 5. quarterly technical progress report  

SciTech Connect

During this first quarter of the second year of the contract activity has involved several different tasks. The author has continued to work on three tasks most intensively during this quarter: the task of implementing the data base for geothermal system temperature-depth, the maintenance of the WWW site with the heat flow and gradient data base, and finally the development of a modeling capability for analysis of the geothermal system exploration data. The author has completed the task of developing a data base template for geothermal system temperature-depth data that can be used in conjunction with the regional data base that he had already developed and is now implementing it. Progress is described.

Blackwell, D.D.

1998-04-25

117

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

118

Investigation of a fossil geothermal system, Hamblin-Cleopatra Volcano, Clark County, Nevada. Final technical report  

SciTech Connect

The Hamblin-Cleopatra volcano, selected for study because erosion and fault displacement have exposed the entire volcanic succession, the intrusive core, a radial dike systems, and sedimentary and volcanic rocks that predate and postdate the volcano, was investigated to estimate the proportions of igneous materials forming lava flows, pyroclastic deposits, intrusive bodies, and reworked debris. Chemical changes in the magma throughout the active period of the volcano were documented. The geothermal system active within the pile after activity ceased was reconstructed. (ACR)

Barker, D.S.

1986-07-28

119

Ground Source Heat Pumps - Geothermal Energy for Anyone, Anywhere: Current Worldwide Activity  

Microsoft Academic Search

At WGC 1995 in Florence a paper was presented that brought to the attention of the worldwide geothermal community the increasing activity in geothermal heat pumps. With increasing pressures for reductions in building energy consumption and rising targets for reductions in CO2 emissions from buildings, the drivers for installing geothermal heat pumps are all going in the right direction. An

R. Curtis; J. Lund; B. Sanner; L. Rybach; G. Hellström

120

Aquifer chemistry of four high-temperature geothermal systems in Iceland  

NASA Astrophysics Data System (ADS)

The deep water feeding wet-steam wells in four high-temperature geothermal areas in Iceland have highly variable salinity as reflected in the chlorine concentrations which vary from 20 to 19000 ppm. Using available values for equilibrium constants, the activities of 26 chemical species involving the major components of the reservoir water have been calculated and quantitative evaluations of solute/ solute, mineral/solute chemical equilibria in these geothermal systems have been made. The unflashed reservoir water is just saturated with calcite. The saline geothermal waters, which represent heated sea-water, are just saturated with anhydrite, but the dilute waters, which are of meteoric origin, are somewhat undersaturated with this mineral. The fluoride mobility is thought to be limited by an ionic exchange reaction where F - replaces some of the OH - in the layered silicates. The pH of the unflashed reservoir water is governed by ionic exchange equilibrium in which all the major cations participitate. At a given temperature it seems likely that the activity of one cation fixes the activities of all the other major cations and hydrogen ion. If this is so and we take all the other chemical equilibria which have been demonstrated to exist for granted, it turns out that the major element composition of the unflashed high-temperature geothermal waters is controlled by two independent variables only. These variables are the temperature and the supply to the water of the incompatible element chlorine, incompatible indicating that this element is not incorporated in the geothermal minerals.

Arnórsson, Stefán; Grönvold, Karl; Sigurdsson, Sven

1978-05-01

121

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

122

Recommendations of the workshop on advanced geothermal drilling systems  

SciTech Connect

At the request of the U.S. Department of Energy, Office of Geothermal Technologies, Sandia National Laboratories convened a group of drilling experts in Berkeley, CA, on April 15-16, 1997, to discuss advanced geothermal drilling systems. The objective of the workshop was to develop one or more conceptual designs for an advanced geothermal drilling system that meets all of the criteria necessary to drill a model geothermal well. The drilling process was divided into ten essential functions. Each function was examined, and discussions were held on the conventional methods used to accomplish each function and the problems commonly encountered. Alternative methods of performing each function were then listed and evaluated by the group. Alternative methods considered feasible or at least worth further investigation were identified, while methods considered impractical or not potentially cost-saving were eliminated from further discussion. This report summarizes the recommendations of the workshop participants. For each of the ten functions, the conventional methods, common problems, and recommended alternative technologies and methods are listed. Each recommended alternative is discussed, and a description is given of the process by which this information will be used by the U.S. DOE to develop an advanced geothermal drilling research program.

Glowka, D.A.

1997-12-01

123

Precious metals in high-temperature geothermal systems in New Zealand  

Microsoft Academic Search

High-temperature geothermal systems are the modern analogue of epithermal precious metal ore deposits. In these systems, gold and silver are transported primarily as bisulfide complexes, with the precious metals being deposited in response to boiling and mixing of the deep geothermal fluid. In order for the geothermal system to produce an economic precious metal deposit within the typical lifetime of

Kevin L. Brown; Stuart F. Simmons

2003-01-01

124

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

125

Analysis of a scaling rate meter for geothermal systems  

SciTech Connect

A research project was conducted to investigate an experimental technique for measuring the rate of formation of mineral scale and corrosion in geothermal systems. A literature review was performed first to identify and evaluate available techniques for measuring scale in heat transfer equipment. As a result of these evaluations, a conceptual design was proposed for a geothermal Scaling Rate Meter (SRM) that would combine features of certain techniques used (or proposed for use) in other applications. An analysis was performed to predict the steady-state performance and expected experimental uncertainty of the proposed SRM. Sample computations were then performed to illustrate the system performance for conditions typical of a geothermal scaling application. Based on these results, recommendations are made regarding prototype SRM construction and testing.

Kreid, D.K.

1980-03-01

126

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

Microsoft Academic Search

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

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

2010-01-01

127

Technical support for geopressured-geothermal well activities in Louisiana  

NASA Astrophysics Data System (ADS)

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.

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

1981-08-01

128

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

129

Design of an isobutane binary cycle geothermal generation system  

NASA Astrophysics Data System (ADS)

A 1000-kW binary cycle geothermal power plant with isobutane as the working medium, which uses geothermal steam and hot water, was successfully run for the first time at Otake, Kyushu, in 1978. The paper discusses the development of this plant, the features of the Otake pilot plant, the outline of the plant, and the main components. The technological feasibility of a future large operating plant is established. Factors such as economy, reliability, and social and environmental acceptability, etc. should be considered before constructing the binary cycle power generation system.

Aikawa, K.

1980-01-01

130

Early Devonian geothermal systems in northeast Scotland: Exploration targets for epithermal gold  

SciTech Connect

Early Devonian geothermal activity is recognized in northeast Scotland by the remnants of silica sinter, a hot-spring manganese deposit, an area of steam alteration, and hydrothermal eruption breccias. At least five systems were active at this time, three of which are located on or near the intersection of major faults and lineaments. Two deposits can be dated as Early Devonian, whereas others show a spatial relation to 408 Ma Caledonian granitoids-the proposed heat sources for the geothermal systems. Fault zones active at this time provided channelways for fluids in the convecting systems. The shallow sections of these systems have been preserved in the Arndilly, Dalroy, Lecht, and Rhynie areas, which is encouraging for gold prospecting. Six targets for epithermal gold exploration are identified: the four areas named above and two areas at the intersection of major faults and lineaments.

Nicholson, K. (Univ. of Auckland, Private Bag (New Zealand))

1989-06-01

131

Thermal Infrared Remote Sensing of the Yellowstone Geothermal System  

Microsoft Academic Search

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,

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

2009-01-01

132

Re-evaluation of the Moyuta geothermal system, Southern Guatemala.  

National Technical Information Service (NTIS)

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/da...

F. Goff A. Adams P. E. Trujillo D. Counce C. Janik

1991-01-01

133

Challenges for Numerical Modeling of Enhanced Geothermal Systems  

Microsoft Academic Search

A recent guest editorial by Wood (2009) pointed out the potential of enhanced geothermal systems (EGS) as a future source of green energy and suggested that EGS offers research opportunities for hydrogeologists seeking to become involved in the worlds energy future. Although EGS may have a bright future as a sustainable, low-carbon emission energy source, significant technical challenges must be

J. P. Fairley; S. E. Ingebritsen; R. K. Podgorney

2010-01-01

134

Characterisation of the Basel 1 enhanced geothermal system  

Microsoft Academic Search

This paper describes the steps that have been undertaken to create an enhanced geothermal system (EGS) at the Deep Heat Mining Project in Basel, Switzerland. Preliminary results from drilling, logging, hydraulic testing and stimulating the Basel 1 well are summarized. The project was suspended following the occurrence of several ‘felt’ microseismic events. Because such events may be an inherent risk

Markus O. Häring; Ulrich Schanz; Florentin Ladner; Ben C. Dyer

2008-01-01

135

ENHANCED GEOTHERMAL SYSTEMS (EGS) WELL CONSTRUCTION TECHNOLOGY EVALUATION SYNOPSIS  

Microsoft Academic Search

A synopsis of a report evaluating well construction technology for Enhanced Geothermal Systems (EGS) is presented. The assessment of well construction technology had two primary objectives: 1. Determining the ability of existing technologies to develop EGS wells. 2. Identifying critical well construction research lines and development technologies that are likely to enhance prospects for EGS viability and improve overall economics.

Yarom Polsky; Douglas Blankenship; Robert J. Swanson; Louis E. Capuano

136

Coupled thermal-hydraulic-chemical modelling of enhanced geothermal systems  

Microsoft Academic Search

The study investigates thermal-, hydraulic- and chemically coupled processes of enhanced geothermal systems (EGS). On the basis of the two existing numerical codes, the finite element program FRACTURE and the geochemical module of CHEMTOUGH, FRACHEM was developed, to simulate coupled thermal-hydraulic-chemical (THC) processes, accounting for the Soultz specific conditions such as the high salinity of the reservoir fluid and the

D. Bächler; T. Kohl

2005-01-01

137

Estimating Well Costs for Enhanced Geothermal System Applications  

Microsoft Academic Search

The objective of the work reported was to investigate the costs of drilling and completing wells and to relate those costs to the economic viability of enhanced geothermal systems (EGS). This is part of a larger parametric study of major cost components in an EGS. The possibility of improving the economics of EGS can be determined by analyzing the major

K. K. Bloomfield; P. T. Laney

2005-01-01

138

Upscaling of Thermal Transport Properties in Enhanced Geothermal Systems  

Microsoft Academic Search

Abstract: Engineered Geothermal Systems (EGS) have garnered significant attention as a possible source of geographically disperse, carbon-free energy without the environmental impact of many other renewable energy sources. However, a significant barrier to the adoption of EGS is the uncertainty in whether a specific site is amenable to engineering and how fluid injection rates can affect, either through stimulation of

S. Johnson; Y. Hao; L. Chiaramonte

2010-01-01

139

Description and operation of Haakon School geothermal heating system  

Microsoft Academic Search

Haakon School is located in the city of Philip, near the Badlands National Park in the southwest quadrant of South Dakota. The town overlies the Madison Formation which is a large-area aquifer. The aquifer has a demonstrated capability to produce geothermal water. A system to tap this potential and heat the Haakon School District buildings in Philip has been in

F. W. Childs; L. D. Kirol; R. D. Sanders; M. J. McLatchy

1997-01-01

140

Description and operation of Haakon School geothermal heating system  

SciTech Connect

Haakon School is located in the city of Philip, near the Badlands National Park in the southwest quadrant of South Dakota. The town overlies the Madison Formation which is a large-area aquifer. The aquifer has a demonstrated capability to produce geothermal water. A system to tap this potential and heat the Haakon School District buildings in Philip has been in operation since November 1980. Five school buildings having a total area of 44,000 ft{sup 2} (4088 ft{sup 2}) are heated with 157{degrees}F (69{degrees}C) water. A single well provides water at a maximum artesian flow of 340 gpm (21.5 L/s), which more than meets the heat demand of the school buildings. Eight buildings in the Philip business district utilize geothermal fluid discharged from the school for space heating. During the 1980-81 heating season, these buildings obtained 75% to 90% of their heat from geothermal fluid. Peak heat delivery of the system is 5.5 million Btu/h (1.61. MJ/s), with an annual energy delivery of 9.5 billion Btu (10 TJ). The geothermal system has operated nearly problem free with the exception of the equipment to remove Radium-226 from the spent fluid. Barium chloride is added to the water to precipitate sulfates containing the radium. Accumulation of precipitates in piping has caused some operational problems.

Childs, F.W.; Kirol, L.D.; Sanders, R.D.; McLatchy, M.J.

1997-12-01

141

Seismic Tomography of the Soufriere of Guadeloupe upper geothermal system  

NASA Astrophysics Data System (ADS)

We present the result of an active seismic tomography experiment that has been conducted on the Soufriere of Guadeloupe, Lesser Antilles, in a joint project including several geophysical studies. The Soufriere Lava Dome constitutes the upper part of la Soufriere very active geothermal system that had its last phreatic eruption in 1976. The Soufriere volcano is known to have been the source of many instabilities leading to major flank collapses. The purpose of these geophysical experiments is then to bring better constraints on the possible zone of mechanical weakness. Three active seismic experiments have thus been conducted on the upper part of the volcano, in coordination with EM experiments in order to scan the same area. We show the results obtained by several profiles that are inverted using a travel-time tomography. The results show very good agreement with resistivity profiles. These results will be used in the future to conduct a joint inversion. In this presentation we focus on the major common features and on major seismic propagation observations.

Coutant, Olivier; Doré, Fabrice; Nicollin, Florence; Beauducel, Francois; Virieux, Jean

2010-05-01

142

Experimental evaluation of a non-azeotropic working fluid for geothermal heat pump system  

Microsoft Academic Search

Geothermal energy resources are found in many countries. A reasonable and efficient utilization of these resources has been a worldwide concern. The application of geothermal heat pump systems (GHPS) can help increase the efficiency of using geothermal energy and reduce the thermal pollution to the earth surface. However, this is only possible with a proper working fluid. In this paper,

L. Zhao

2004-01-01

143

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

Microsoft Academic Search

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

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

2001-01-01

144

Enhanced Geothermal Systems (EGS) R&D Program: Monitoring EGS-Related Research  

Microsoft Academic Search

This report reviews technologies that could be applicable to Enhanced Geothermal Systems development. EGS covers the spectrum of geothermal resources from hydrothermal to hot dry rock. We monitored recent and ongoing research, as reported in the technical literature, that would be useful in expanding current and future geothermal fields. The literature review was supplemented by input obtained through contacts with

Lynn McLarty; Daniel Entingh; Clifton Carwile

2000-01-01

145

Assessment of the geothermal space heating system at Rotorua Hospital, New Zealand  

Microsoft Academic Search

Rotorua township is situated on top of a shallow geothermal reservoir within the Taupo Volcanic Zone of New Zealand. The resource is easy to access for private users and is commonly used for domestic and commercial heating. The Rotorua Hospital is located on one of the up flows of the geothermal reservoir and uses a doublet geothermal heating system that

Christopher Steins; Sadiq J. Zarrouk

146

Geothermal energy in Uganda, country update  

Microsoft Academic Search

Recent studies on the Uganda geothermal systems have focused on three geothermal prospects, Katwe, Buranga and Kibiro, all located in the tectonically active and Recent volcanic belt in the Western Rift valley along the border of Uganda and the Democratic Republic of Congo. Geothermal systems and saline and fresh water lakes characterize the Rift Valley. The three areas were chosen

Godfrey Bahati

147

REVIVAL OF GRASS-ROOTS GEOTHERMAL EXPLORATION IN THE GREAT BASIN (WHERE TO LOOK FOR NEW GEOTHERMAL FIELDS) - A NEW APPROACH TO ASSESSING GEOTHERMAL POTENTIAL USING A GEOGRAPHIC INFORMATION SYSTEM parts IV and V  

Microsoft Academic Search

We propose to expand the existing GIS of geothermal systems in the Great Basin to include several key new features: 1) improved predictive maps of geothermal favorability based on new digital data on crustal strain, fault displacements, heat flux, and other data, 2) maps predicting which portions of the Great Basin are most likely to conceal geothermal systems, and 3)

Mark Coolbaugh; Rick Zehner; Corné Kreemer; Don Sawatzky; Gary Oppliger; David Blackwell; Lisa Shevenell; Jim Taranik; Gary Raines; Jim Faulds

148

Geothermal aquaculture project: Real Property Systems Inc. , Harney Basin, Oregon  

SciTech Connect

Real Property Systems Inc., (RPS) owns two parcels in the vicinity of Harney Lake, Oregon. One parcel is 120 acres in size, the other is 200 acres. A study concludes that the 200 acre parcel has the greater potential for geothermal development. RPS is interested in an aquaculture operation that produces fresh water prawns, (Macrobrachium rosenbergii) for the market. To supply the heat necessary to maintain the ideal temperature of 82/sup 0/F desired for these prawns, a geothermal resource having a 150/sup 0/F temperature or higher, is needed. The best estimate is that 150/sup 0/F water can be found from a minimum 1090 feet depth to 2625 feet, with no absolute assurances that sufficient quantities of geothermal waters exist without drilling for the same. This study undertakes the preliminary determination of project economics so that a decision can be made whether or not to proceed with exploratory drilling. The study is based on 10 acres of ponds, with a peak requirement of 2500 gpm of 150/sup 0/F geothermal water.

Not Available

1981-08-14

149

Seal/lubricant systems for geothermal drilling equipment  

SciTech Connect

The development and testing of seals and lubricants for journal-type roller-cone rock bits for drilling into geothermal reservoirs at temperatures over 260/sup 0/C (500/sup 0/F) are described. The conditions experienced by seals and lubricants subjected to geothermal drilling are reviewed along with the basic design requirements for roller-cone bit seals and journal bearing lubricants. Two unique test facilities are described: a seal test machine which simulates pressures, temperatures, and mechanical eccentricities, and a lubricant tester capable of evaluating load-bearing ability at temperature and pressure. Three candidate elastomeric compounds demonstrated 288/sup 0/C (550/sup 0/F) capability and several others demonstrated 260/sup 0/C (500/sup 0/F) or greater capability. Successful elastomeric seal candidates were proprietary compounds based on EPDM, Kalrez, and/or Viton polymers. Three mechanical seals for reservoir temperatures over 288/sup 0/C (550/sup 0/F) are presented. Lubricant screening tests on more than 50 products are summarized, and several newly developed lubricants which meet both the compatibility and lubrication requirements are described. Several seal/lubricant systems are recommended for laboratory or field geothermal drilling tests in roller-cone drill bits. The future availability of drill bits for geothermal use is discussed, as well as the potential spinoffs of the program findings for nongeothermal roller-cone bits.

Hendrickson, R.R.; Winzenried, R.W.

1980-07-01

150

Environmental impacts of open loop geothermal system on groundwater  

NASA Astrophysics Data System (ADS)

Application of renewable energies such as sunlight, wind, rain, tides, waves and geothermal heat has gradually increased to reduce emission of CO2 which is supplied from combustion of fossil fuel. The geothermal energy of various renewable energies has benefit to be used to cooling and heating systems and has good energy efficiency compared with other renewable energies. However, open loop system of geothermal heat pump system has possibility that various environmental problems are induced because the system directly uses groundwater to exchange heat. This study was performed to collect data from many documents such as papers and reports and to summarize environmental impacts for application of open loop system. The environmental impacts are classified into change of hydrogeological factors such as water temperature, redox condition, EC, change of microbial species, well contamination and depletion of groundwater. The change of hydrogeological factors can induce new geological processes such as dissolution and precipitation of some minerals. For examples, increase of water temperature can change pH and Eh. These variations can change saturation index of some minerals. Therefore, dissolution and precipitation of some minerals such as quartz and carbonate species and compounds including Fe and Mn can induce a collapse and a clogging of well. The well contamination and depletion of groundwater can reduce available groundwater resources. These environmental impacts will be different in each region because hydrogeological properties and scale, operation period and kind of the system. Therefore, appropriate responses will be considered for each environmental impact. Also, sufficient study will be conducted to reduce the environmental impacts and to improve geothermal energy efficiency during the period that a open loop system is operated. 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).

Kwon, Koo-Sang; Park, Youngyun; Yun, Sang Woong; Lee, Jin-Yong

2013-04-01

151

Geothermal system at 21°N, East Pacific Rise: physical limits on geothermal fluid and role of adiabatic expansion  

Microsoft Academic Search

Pressure-volume-temperature relations for water at the depth of the magma chamber at 21°N on the East Pacific Rise suggest that the maximum subsurface temperature of the geothermal fluid is about 420°C. Both the chemistry of the discharging fluid and thermal balance considerations indicate that the effective water\\/rock ratios in the geothermal system are between 7 and 16. Such low ratios

J. L. BISCHOFF

1980-01-01

152

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

153

Geothermal System at 21 degrees N, East Pacific Rise: Physical Limits on Geothermal Fluid and Role of Adiabatic Expansion  

Microsoft Academic Search

Pressure-volume-temperature relations for water at the depth of the magma chamber at 21 degrees N on the East Pacific Rise suggest that the maximum sub-surface temperature of the geothermal fluid is about 420 degrees C. Both the chemistry of the discharging fluid and thermal balance considerations indicate that the effective water\\/rock ratios in the geothermal system are between 7 and

James L. Bischoff

1980-01-01

154

Natural analogs for enhanced heat recovery from geothermal systems  

SciTech Connect

High-temperature hydrothermal systems are physically and chemically zoned with depth. The energy input is from a magmatic zone, intruded by igneous bodies, that may also contribute variable amounts of magmatic fluid to the system. The heat source is directly overlain by a section of rocks, that due to their elevated temperature, respond to stress in a ductile fashion. The ductile zone is, in turn, overlain by a section of rocks that respond to stress in a brittle fashion, where water is able to circulate through fractures (the geothermal reservoir) and will be termed the hydrothermal circulation zone. Ancient and modern high-temperature geothermal systems show a predictable sequence of evolutionary events affecting these stratified zones. Metamorphic core complexes are uplifts, formed in highly extended terrains, that expose fossil brittle-ductile transition zones. Formerly ductile rocks have had brittle fractures superimposed on them, and meteoric hydrothermal systems are associated with the brittle fracturing. Porphyry copper deposits typically evolve from magmatic to meteoric hydrothermal systems. At the Larderello geothermal system, the brittle- ductile transition has been mapped using reflection seismology, and the zone has been penetrated by the San Pompeo 2 well where temperatures >420°C were encountered. Although neo-granitic dikes have been penetrated by drilling in the Larderello area, the brittle- ductile transition is largely above the inferred plutonic heat source. In the Geysers system, in contrast, the present steam system has been superimposed on young plutonic rocks and the inferred brittle-ductile transition is present at a depth of about 4.7 km within the plutonic rocks. As hydrothermal reservoirs are depleted, or surface facilities are restricted by environmental considerations, interest will turn to the deeper portions of known systems. Japan already has an aggressive program to develop Deep-seated and Magma-Ambient resources. This program, as well as others that develop methods for the mining of heat past the stage of primary production, will be termed Enhanced Heat Recovery (EHR). Examples of the evolution of natural systems suggest the methods by which deep geothermal systems can be exploited. The key to the exploitation of deep geothermal systems is successful injection of water into rocks above the brittle-ductile transition, producing steam, cooling the rocks and driving the brittle-ductile transition to deeper levels. Under this scenario, injection wells may be more expensive and require more thoughtful planning than production wells.

Nielson, Dennis L.

1996-01-24

155

Current California legislative and regulatory activity impacting geothermal hydrothermal commercialization: a monitoring report. Report No. 1017  

SciTech Connect

Four key geothermal-impacting bills presently before the California legislature are described. Two deal with state financial backing for geothermal projects. The third relates to the use of the state's share of the BLM geothermal revenues and the fourth to the protection of sensitive hot springs. The current regulatory activities of the California Energy Commission, the California Division of Oil and Gas, and the counties are discussed. (MHR)

Not Available

1980-01-20

156

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

157

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

158

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

159

Vertical arrays for fracture mapping in geothermal systems  

SciTech Connect

In collaboration with UNOCAL Geothermal Operations, Los Alamos National Laboratory assessed the feasibility of using vertical arrays of borehole seismic sensors for mapping of microseismicity in The Geysers geothermal field. Seismicity which arises from minute displacements along fracture or fault surfaces has been shown in studies of seismically active oil reservoirs to be useful in identifying fractures affected by and possibly contributing to production. Use of retrievable borehole seismic packages at The Geysers was found to reduce the threshold for detection of microearthquakes by an estimated 2--3 orders of magnitude in comparison to surface-based sensors. These studies led to the design, materials selection, fabrication, and installation of a permanent array of geophones intended for long term seismic monitoring and mapping of fractures in the vicinity of the array at The Geysers.

Albright, J.N. [Los Alamos National Lab., NM (United States); Rutledge, J.T.; Fairbanks, T.D. [Nambe Geophysics, Inc. (United States); Thomson, J.C. [Lithos Inc. (United States); Stevenson, M.A. [Petroleum Geo-Services (United States)

1998-12-01

160

Geology of the Beowawe geothermal system, Eureka and Lander Counties, Nevada  

SciTech Connect

A geologic study is described undertaken to evaluate the nature of structural and stratigraphic controls within the Beowawe geothermal system, Eureka and Lander Counties, Nevada. This study includes geologic mapping at a scale of 1:24,000 and lithologic logs of deep Chevron wells. Two major normal fault systems control the configuration of the Beowawe geothermal system. Active hot springs and sinter deposits lie along the Malpais Fault zone at the base of the Malpais Rim. The Malpais Rim is one of several east-northeast-striking, fault-bounded cuestas in north central Nevada. A steeply inclined scarp slope faces northwest towards Whirlwind Valley. The general inclination of the volcanic rocks on the Malpais dip slope is 5/sup 0/ to 10/sup 0/ southeast.

Struhsacker, E.M.

1980-07-01

161

Removal of carbon dioxide in geothermal power systems  

Microsoft Academic Search

A process for removing carbon dioxide in geothermal power generating processes employing a geothermal fluid such as geothermal brine containing carbon dioxide, to improve the efficiency of geothermal power generation, comprises introducing an aqueous alkaline solution, preferably an aqueous calcium hydroxide solution, into a vapor stream obtained from the brine during power generation, to remove carbon dioxide from the stream.

Wahl

1982-01-01

162

Applied Microearthquake Techniques for Geothermal Resource Development  

Microsoft Academic Search

Geothermal areas are often associated with microearthquake activity (Foulger, 1982; Foulger and Long, 1984), and these earthquakes have often been used to learn more about both exploited and unexploited geothermal systems. In recent years, interest in exploiting geothermal energy has increased greatly, accompanied by interest and investment in refining microearthquake analysis techniques, to increase their value in reservoir- development decision

Gillian R. Foulger; Bruce R. Julian

163

Thirteenth workshop on geothermal reservoir engineering: Proceedings  

Microsoft Academic Search

PREFACE The Thirteenth Workshop on Geothermal Reservoir Engineering was held at Stanford University on January 19-21, 1988. Although 1987 continued to be difficult for the domestic geothermal industry, world-wide activities continued to expand. Two invited presentations on mature geothermal systems were a keynote of the meeting. Malcolm Grant presented a detailed review of Wairakei, New Zealand and highlighted plans for

H. J. Jr. Ramey; P. Kruger; R. N. Horne; W. E. Brigham; F. G. Miller; J. W. Cook

1988-01-01

164

Geothermal activity in the subglacial Katla caldera, Iceland, 1999-2005, studied with radar altimetry  

Microsoft Academic Search

The Katla caldera is located under the Myrdalsjokull ice cap and is one of the most hazardous volcanoes in Iceland due to major jokulhlaups that accompany eruptions. Subglacial geothermal activity is manifested in several 10-50 m deep depressions (ice cauldrons) within and at the caldera rim and the total geothermal heat output is of the order of a few hundred

Magnus T. GUÐMUNDSSON; Þordis HOGNADOTTIR

165

Geothermal activity in the subglacial Katla caldera, Iceland, 1999-2005, studied with radar altimetry  

Microsoft Academic Search

The Katla caldera is located under the Mýrdalsjökull ice cap and is one of the most hazardous volcanoes in Iceland due to major jökulhlaups that accompany eruptions. Subglacial geothermal activity is manifested in several 10-50 m deep depressions (ice cauldrons) within and at the caldera rim and the total geothermal heat output is of the order of a few hundred

Magnús T. Gudmundsson; Pórdís Höganadóttir; Arnór Bergur Kristinsson; Snaebjörn Gudbjörnsson

2007-01-01

166

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

167

Geothermal energy program overview  

NASA Astrophysics Data System (ADS)

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 within 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 percent of the total U.S. 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 U.S. 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.

1991-12-01

168

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

169

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

170

Clay minerals related to the hydrothermal activity of the Bouillante geothermal field (Guadeloupe)  

Microsoft Academic Search

The geothermal field of Bouillante (Guadeloupe, FWI) is a high-enthalpy hydrothermal system emplaced in submarine volcanoclastic formations (hyaloclastites, scarce lava flows) and subaerial formations (andesitic lava flows, pyroclastites, lahars) which belong to the Lesser Antilles arc. Three directional wells were drilled in 2001 to optimize the productivity of the geothermal field up to 15 MWe and to investigate the vertical distribution

A. Mas; D. Guisseau; P. Patrier Mas; D. Beaufort; A. Genter; B. Sanjuan; J. P. Girard

2006-01-01

171

Coupled reactive flow modeling with declining reactivity in fractured geothermal systems  

NASA Astrophysics Data System (ADS)

Changes in permeability and fluid flow within geothermal systems are driven by geochemical reactions, advective and diffusive transport of heat and solute mass, and evolving thermal and mechanical environments. Representation of these simultaneous processes in numerical models is required for the characterization and simulation of natural geothermal systems. However, identifying and developing mathematical representations for all of the relevant mechanisms that control system behavior presents a major challenge. We have developed two-dimensional simulations of physical and chemical evolution in fractured granite under geothermal conditions with temperatures ranging from 150-300 °C. The goal of this study is to help identify possible sources for existing discrepancies between model results and laboratory-based measurements by adding a new mathematical formulation to the code TOUGHREACT. The revised code is designed to further quantify the link between the progressive evolution of reaction rates and alteration mineralogy. We explicitly couple reaction rates to mineral precipitation/dissolution effects by using an exponential function that defines evolving reactive surface areas in terms of each of the following (i) the accumulated total secondary mineral volume fraction, (ii) the accumulated clay (smectite) portion of the secondary mineral volume fraction, and (iii) the net change in mineral volume fraction (combined effects of dissolution and precipitation). We evaluate the performance of these three modified approaches by comparing simulation results to detailed laboratory measurements of fluid compositions, mineral abundances, and permeability changes in fractured Westerly granite and to previous one-dimensional simulations in which reactive surface areas were adjusted with time to match the observed fracture permeability history. The simulation results offer a potentially useful means of quantifying reactivity loss and of examining the extent to which secondary mineral precipitation controls primary mineral dissolution. The two-dimensional models also allow us to consider the importance of diffusion in controlling reaction behavior. We conclude that mathematically linking reactivity loss to declining surface area may be a viable way to obtain more accurate predictions of the spatial and temporal changes of key geothermal system properties (e.g., permeability, mineral compositions, and solute concentrations) over extended periods of time. Our findings suggest that modeling approaches that do not incorporate a mechanism for rapid changes in reactive surface area may over predict the rate of fracture permeability decay. Consequently, this work also implies that some fraction of the increased permeability resulting from fracture formation and reactivation in tectonically active geothermal systems may be maintained over significant time intervals. Therefore, the models provide a potential framework for predicting the long-term behavior of natural geothermal systems.

Palguta, J.; Williams, C. F.; Ingebritsen, S.; Hickman, S.; Sonnenthal, E. L.

2011-12-01

172

Process Control System of the Mutnovskaya Geothermal Power Plant  

SciTech Connect

The experience of creating software and algorithms for automatic process control at the Mutnovskaya geothermal power plant (GTPP) on the basis of the Teleperm ME automation system is presented. The heat cycle and special features of the heat flow diagram of the power plant are briefly described. The engineering solutions used, the structure of the system, and the principles of process control at the Mutnovskaya GTPP are considered. Special attention is devoted to the turbine regulator that consists of several regulating units because of the great number of problems solved by control valves; each regulating unit solves control problems depending on the mode of operation of the power generating set.

Idzon, O. M.; Ivanov, V. V.; Ilyushin, V. V.; Nikol'skii, A. I. [Interavtomatika Company, VO Tekhnopromeksport Federal State Unitary Enterprise, Nauka Company (Russian Federation)

2004-01-15

173

Estimating Well Costs for Enhanced Geothermal System Applications  

SciTech Connect

The objective of the work reported was to investigate the costs of drilling and completing wells and to relate those costs to the economic viability of enhanced geothermal systems (EGS). This is part of a larger parametric study of major cost components in an EGS. The possibility of improving the economics of EGS can be determined by analyzing the major cost components of the system, which include well drilling and completion. Determining what costs in developing an EGS are most sensitive will determine the areas of research to reduce those costs. The results of the well cost analysis will help determine the cost of a well for EGS development.

K. K. Bloomfield; P. T. Laney

2005-08-01

174

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

175

Life-cycle analysis results of geothermal systems in comparison to other power systems  

Microsoft Academic Search

A life-cycle energy and greenhouse gas emissions analysis has been conducted with Argonne National Laboratory's expanded Greenhouse Gases, Regulated Emissions, and Energy Use in Transportation (GREET) model for geothermal power-generating technologies, including enhanced geothermal, hydrothermal flash, and hydrothermal binary technologies. As a basis of comparison, a similar analysis has been conducted for other power-generating systems, including coal, natural gas combined

J. L. Sullivan; C. E. Clark; J. Han; M. Wang

2010-01-01

176

Beneficial effects of groundwater entry into liquid-dominated geothermal systems  

SciTech Connect

In all active liquid-dominated geothermal systems there is continuous circulation of mass and transfer of heat, otherwise they would slowly cool and fade away. In the natural state these systems are in dynamic equilibrium with the surrounding colder groundwater aquifers. The ascending geothermal fluids cool conductively, boil, or mix with groundwaters, and ultimately may discharge at the surface as fumaroles or hot springs. With the start of fluid production and the lowering of reservoir pressure, the natural equilibrium is disrupted and cooler groundwater tends to enter the reservoir. Improperly constructed or damaged wells, and wells located near the margins of the geothermal system, exhibit temperature reductions (and possibly scaling from mixing of chemically distinct fluids) as the cooler-water moves into the reservoir. These negative effects, especially in peripheral wells are, however, compensated by the maintenance of reservoir pressure and a reduction in reservoir boiling that might result in mineral precipitation in the formation pores and fractures. The positive effect of cold groundwater entry on the behavior of liquid-dominated system is illustrated by using simple reservoir models. The simulation results show that even though groundwater influx into the reservoir causes cooling of fluids produced from wells located near the cold-water recharge area, it also reduces pressure drawdown and boiling in the exploited zone, and sweeps the heat stored in the reservoir rocks toward production wells, thus increasing the productive life of the wells and field. 9 refs.

Lippmann, M.J. (Lawrence Berkeley Lab., CA (USA)); Truesdell, A.H. (Geological Survey, Menlo Park, CA (USA))

1990-04-01

177

Detection and Characterization of Hydraulically Active Fractures in a Carbonate Aquifer: Results from Geophysical and Hydrochemical Measurements Along a 260-m-deep Borehole in the Combioula Geothermal System, Western Swiss Alps  

NASA Astrophysics Data System (ADS)

In mountainous regions, pronounced topography, complex geology, and highly permeable geological formations and/or deep-reaching faults and fractures largely govern the development of deep water circulations. In this context, fractured aquifers are of particular interest and the detection and hydraulic characterization of the fractures is a correspondingly important task. Here, in addition to traditional hydrogeological techniques, borehole geophysical measurements were conducted in a fractured deep carbonate aquifer located in the Combioula geothermal system in the western Swiss Alps. The objective of the study was to detect and characterize the hydraulically active fractures along a 260-m-deep borehole through the integration of a comprehensive suite of geophysical well-log data and hydrochemical analysis. Specifically, we wanted to relate the geophysical signals to the fracture network and to examine the sensitivity of the different methods to the flow of groundwater inside the fractures. Although a number of geophysical borehole logging techniques are known to be sensitive to the presence and physical character of fractures, most methods do not provide information with regard to their hydraulic activity. This problem is potentially alleviated through self-potential (SP) measurements, which exhibit a direct sensitivity to fluid flow. Our results illustrate the potential of SP logging for complementing other geophysical logging techniques for distinguishing between hydraulically active and non-active fractures as well as for determining the flow direction within the fractures. The results further indicate that the hydrochemical evidence proved to be critical for the interpretation of the SP measurements. This work may help to open the door for a quantitative interpretation of SP logs with regard to fracture permeability.

Suski, B.; Ladner, F.; Baron, L.; Vuataz, F.; Holliger, K.

2007-12-01

178

Tectonic framework of hydrothermal and geothermal systems in the Menderes Massif, western Turkey  

Microsoft Academic Search

The Menderes Massif in western Turkey lies at the eastern margin of the Hellenic subduction zone's continental backarc. Substantial hydrothermal alteration and geothermal activity have accompanied Miocene to recent extensional tectonics. Here we propose that the locations of Cenozoic magmatic, hydrothermal and geothermal activity are controlled by structures that formed to accommodate an overall E-W gradient in the magnitude of

Klaus Gessner; Alok Porwal; Vanessa Markwitz; Francis Wedin

2010-01-01

179

Induced seismicity at the Paralana Enhanced Geothermal System, South Australia  

NASA Astrophysics Data System (ADS)

Induced seismicity is generally associated with geothermal exploitations through different mechanisms like pore-pressure increase, temperature or chemical changes. The locations and source parameters of microearthquakes are increasingly used as a tool to monitor the response of the reservoir subjected to fluid stimulations. However, our understanding of the relationship between induced seismicity and exploration parameters remains limited, notably because it depends on local and regional geological conditions (stress field, rocks properties, extent of fault and fractures …). In order to make correct interpretation, precise characterization of the geothermal site is then essential. For example, a wrong velocity model will lead to an erroneous earthquake location, particularly in the absence of calibration shots. Similarly, many converted phases could be generated within a complex media, increasing the difficulty to pick phases correctly. We present here our results on the characterization of a geothermal site, Paralana, in South Australia using complementary passive and active seismic methods. The project aims to exploit natural heating from a radiogenic basement. A ~4000 m deep well was stimulated during 5 days in July 2011. More than 7000 microearthquakes were induced and recorded by a network composed of 20 stations (boreholes and surface stations). Automatic methods allowed us to process consistently the large amount of data. A minimum of 25 events per hour were detected from the beginning of the injection, increasing almost conjunctly with flow rate. The maximum seismicity rate reached 100 events per hour, the last day of injection. Active seismic methods were applied to build a 3D velocity model and used to improve the earthquake locations that finally cluster at the bottom of the well. Furthermore, to define the origin of an unknown phase, 3D ray-tracing modeling was systematically applied to test different scenarios. Actual results show that in term of arrival time, these phases most likely correspond to S-to-P converted waves on some interfaces at depth.

Albaric, J.; Langet, N.; Hasting, M.; Oye, V.; Lecomte, I.; Messeiller, M.; Iranpour, K.; Reid, P.; Llanos, E. M.

2012-04-01

180

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

181

Exploration of a Basin and Range-Type Geothermal System Using Soil pH Analysis  

Microsoft Academic Search

The Socorro Peak, NM Known Geothermal Reservoir Area (KGRA) is a Basin and Range-type extentional-fault geothermal system boasting thermal gradients upwards of 420 mW\\/m3 in an uplift Precambrian fault block. Structural and geophysical evidence suggests that a low-to-mid temperature (60-100C) geothermal aquifer may reside within the fault-bounded alluvial basin, capped and insulated by over 1000meters of Tertiary mudstone aquitard strata

L. Owens; G. Hill; D. I. Norman

2005-01-01

182

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

183

Diffuse and focused carbon dioxide and methane emissions from the Sousaki geothermal system, Greece  

Microsoft Academic Search

We report first data on chemical composition of the gas emitted by the geothermal system of Sousaki, Greece. Gas manifestations display typical geothermal gas composition with CO2 as the main component and CH4 and H2S as minor species. Soil gas composition derives from the mixing of two end-members (atmospheric air and geothermal gas). Soil CO2 fluxes range from<2 to 33,400

W. D'Alessandro; L. Brusca; K. Kyriakopoulos; S. Rotolo; G. Michas; M. Minio; G. Papadakis

2006-01-01

184

Opportunities for support of geothermal energy activities from Petroleum Violation Escrow funds  

SciTech Connect

The purpose of this document is to provide a reference for the geothermal community regarding the extent to which Petroleum Violation Escrow (PVE) funds might be employed by states to fund research, development, demonstration and applications pertaining to geothermal energy resources. The document highlights the background and status of the PVE funds being disbursed through state energy agencies and summarizes the types of energy-related activities being conducted with these funds and the process used to select and approve these activities. These funds provides a mechanism for expanding the contribution of geothermal technologies to domestic energy conservation and security.

Not Available

1988-06-01

185

Rock Mechanics and Enhanced Geothermal Systems: A DOE-sponsored Workshop to Explore Research Needs  

Microsoft Academic Search

This workshop on rock mechanics and enhanced geothermal systems (EGS) was held in Cambridge, Mass., on June 20-21 2003, before the Soil and Rock America 2003 International Conference at MIT. Its purpose was to bring together experts in the field of rock mechanics and geothermal systems to encourage innovative thinking, explore new ideas, and identify research needs in the areas

Francois Heuze; Peter Smeallie; Derek Elsworth; Joel L. Renner

2003-01-01

186

Enhanced Geothermal Systems Project Development Solicitation - Final Report - 09\\/30\\/2000 - 02\\/01\\/2001  

Microsoft Academic Search

The Enhanced Geothermal System concept is to develop the technology required to extract energy from the reduced permeability zones that underlie all high-temperature geothermal systems. Our concept is that injection wells will be drilled into the high temperature zone. The wells will identify fractures that are only poorly connected to the overlying reservoir. Water injected into these fractures will cause

Nielson; Dennis L

2001-01-01

187

Boiling and dilution in the shallow portion of the Waiotapu geothermal system, New Zealand  

Microsoft Academic Search

The Waiotapu geothermal system is the largest in terms of surface extent and heat flow (17 km 2 and 600 MW, respectively) of the 20 major geothermal systems in the Taupo Volcanic Zone, New Zealand. Two extinct dacite cones and a rhyolite dome rise about 500 m above the Waiotapu valley. The majority of thermal features occurs in the valley

Jeffrey W. Hedenquist

1991-01-01

188

Marketing the Klamath Falls Geothermal District Heating system  

SciTech Connect

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 start up. The revenue from these buildings, however, did not cover the entire cost of operating the system. As a result, the city was faced with a difficult decision - develop the revenue required to make the system self-supporting or shut it down. As a result, a marketing strategy for the system was developed. A flat rate was developed in which the rate is negotiable, but for most customers approximates 50% of the gas bill. In addition, the flat rate reduced customer retrofit costs because it is not necessary to buy a meter. Finally, the flat rate is a guaranteed value for the first 10 years of the contract. To reduce retrofit costs, the new marketing plan eliminates the requirement for a customer heat exchanger. New customers are now connected directly into the distribution system with district loop water used as the building heating medium. The state operates two programs which have been used in the marketing plan. The first of these is available only to taxable entities and is referred to as the Business Energy Tax Credit (BETC). This program offers business a 35% tax credit on the costs associated with connection to the geothermal district heat system (retrofit, design, permits, etc.). The second state program is the Small Energy Loan Program (SELP). This program will loan the entire cost of the energy project to the customer. The new marketing strategy for the Klamath Falls system has concentrated on offering the customer an attractive and easy to understand rate structure, reduced retrofit cost and complexity for this building along with an attractive package of financing and tax credits. 1 tab.

Rafferty, K. (Geo-Heat Center, Klamath Falls, OR (United States))

1993-08-01

189

The Coso Geothermal Area: A Laboratory for Advanced MEQ Studies for Geothermal Monitoring  

Microsoft Academic Search

The permanent 16-station network of three-component digital seismometers at the Coso geothermal area, California, supplemented by 14 temporary instruments deployed in connection with the DOE Enhanced Geothermal Systems (EGS) Project, provides high-quality microearthquake (MEQ) recordings that are well suited to monitoring a producing geothermal area. We are currently using these data to investigate structure and active processes within the geothermal

Bruce R. Julian; Gillian R. Foulger; Keith Richards-Dinger

190

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

191

Sperry Low Temperature Geothermal Conversion System, Phase 1 and Phase 2. Volume 3: Systems description  

NASA Astrophysics Data System (ADS)

The major fraction of hydrothermal resources with the prospect of economic usefulness for the generation of electricity are in the 300(0)F to 425(0)F temperature range. Cost effective conversion of the geothermal energy to electricity requires new ideas to improve conversion efficiency, enhance brine flow, reduce plant costs, increase plant availability, and shorten the time between investment and return. The problems addressed are those inherent in the geothermal environment, in the binary fluid cycle, in the difficulty of efficiently converting the energy of a low temperature resource, and in geothermal economics some of these problems are explained. The energy expended by the down hole pump; the difficulty in designing reliable down hole equipment; fouling of heat exchanger surfaces by geothermal fluids; the unavailability of condenser cooling water at most geothermal sites; the large portion of the available energy used by the feed pump in a binary system; the pinch effect, a loss in available energy in transferring heat from water to an organic fluid; flow losses in fluids that carry only a small amount of useful energy to begin with; high heat exchanger costs, the lower the temperature interval of the cycle, the higher the heat exchanger costs in $/kW; the complexity and cost of the many auxiliary elements of proposed geothermal plants; and the unfortunate cash flow vs. investment curve caused by the many years of investment required to bring a field into production before any income is realized.

Matthews, H. B.

192

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

193

Assessing the role of ancient and active geothermal systems in oil-reservoir evolution in the eastern Basin and Range province, western USA. Annual progress report, June 1, 1992--May 31, 1993  

SciTech Connect

Results of our research on the oil fields of the Basin and Range province of the western USA continue to support the following concept: Convecting, moderate-temperature geothermal systems in this region have fostered and in some cases critically influenced the generation, migration, and entrapment of oil. At one Basin-Range field (Grant Canyon), oil-bearing and aqueous fluid inclusions in late-stage hydrothermal quartz were entrapped at temperatures comparable to those now prevailing at reservoir depths (120--130{degrees}C); apparent salinities of the aqueous varieties match closely the actual salinity of the modern, dilute oil-field waters. The inclusion-bearing quartz has the oxygen-isotopic signature for precipitation of the mineral at contemporary temperatures from modern reservoir waters. Measured and fluid-inclusion temperatures define near-coincident isothermal profiles through the oil-reservoir interval, a phenomenon suggesting ongoing heat and mass transfer. These findings are consistent with a model whereby a still-active, convectively circulating, meteoric-hydrothermal system: (1) enhanced porosity in the reservoir rock through dissolution of carbonate; (2) hydrothermally sealed reservoir margins; (3) transported oil to the reservoirs from a deep source of unknown size and configuration; and (4) possibly accelerated source-rock maturation through an increase in the local thermal budget. Grant Canyon and other Basin-Range oil fields are similar to the oil-bearing, Carlin-type, sediment-hosted, disseminated gold deposits of the nearby Alligator Ridge district. The oil fields could represent either weakly mineralized analogues of these deposits, or perhaps an incipient phase in their evolution.

Hulen, J.B.

1993-07-01

194

Outstanding Issues in the Assessment of Enhanced Geothermal Systems Resources  

NASA Astrophysics Data System (ADS)

The successful implementation of Enhanced Geothermal Systems (EGS) technology has the potential to dramatically expand both the magnitude and spatial extent of geothermal energy production, and the U.S. Geological Survey (USGS) has been working to develop a comprehensive EGS resource assessment for the United States. However, a number of outstanding scientific and technical issues must be resolved in order to ensure the accuracy and reliability of this assessment. Among these are determining those conditions under which it is possible to replicate the high average permeability (approximately 10-15 to 10-13 m2) characteristic of natural hydrothermal reservoirs, evaluating the likely heterogeneity of fracture permeability within EGS reservoirs and its influence on the geothermal recovery factor, Rg, which is defined as the ratio of produced thermal energy to the thermal energy contained in the stimulated volume comprising the reservoir, and improving estimates of temperature in the upper crust to better quantify the thermal energy available at those depths viable for EGS reservoir creation. Models for the development of fracture permeability from the shear slip along pre-existing natural fractures induced by hydraulic stimulation indicate that production from EGS reservoirs will be sensitive to the influence of effective stress and rock properties on the processes of shear fracture formation and closure. Calibration of model parameters with results from EGS field experiments and demonstration projects suggests that sufficient permeability may be difficult to attain through shear stimulation at depths greater than approximately 6 km, particularly in regions characterized by high normal stress on pre-existing faults and fractures. In addition, the expected heterogeneity of fracture permeability within EGS reservoirs may limit Rg to values on the order of 0.05 to 0.1, which is at the lower end of the observed range for producing natural geothermal reservoirs. Although there are significant gaps in the spatial coverage of heat flow measurements in much of the United States and some uncertainty in the estimation of thermal properties at depth, analysis of the existing thermal data indicates that even with the possible constraints outlined above, large areas of the western United States will be suitable for EGS development. However, this provisional interpretation is compromised by the limited number of cases in which model predictions can be compared to laboratory or in situ data. The key challenge for improved EGS resource assessments is acquiring and interpreting comprehensive laboratory and field data that can provide quantitative constraints on the recovery of heat from EGS reservoirs in diverse settings.

Williams, C.; Deangelo, J.

2010-12-01

195

Quantitative analysis of existing conditions and production strategies for the Baca geothermal system, New Mexico  

Microsoft Academic Search

The Baca geothermal reservoir and adjacent aquifers in the Jemez Mountains of New Mexico comprise an integrated hydrogeologic system. Analysis of the geothermal reservoir either under natural conditions or subject to proposed development should account for the mass (water) and energy (heat) balances of adjacent aquifers as well as the reservoir itself. A three-dimensional model based on finite difference approximation

Charles R. Faust; James W. Mercer; Stephen D. Thomas; W. Pete Balleau

1984-01-01

196

Characterization of geothermal systems in volcano-tectonic depressions : Japan and New Zealand  

Microsoft Academic Search

Characterization of geothermal systems was investigated in two regional scale volcano- tectonic depressions, the Kuju-Beppu Graben (KBG), in Japan, and the young-Taupo Volcanic Zone (TVZ) in New Zealand. The distribution patterns of geothermal fields are different. In the KBG they are restricted to areas on and behind only the youngest volcanic front, but are evenly spaced through- out the whole

Shiro Tamanyu; C. Peter Wood

197

Quantitative Analysis of Existing Conditions and Production Strategies for the Baca Geothermal System, New Mexico  

Microsoft Academic Search

The Baca geothermal reservoir and adjacent aquifers in the Jemez Mountains of New Mexico comprise an integrated hydrogeologic system. Analysis of the geothermal reservoir either under natural conditions or subject to proposed development should account for the mass (water) and energy (heat) balances of adjacent aquifers as well as the reservoir itself. A three-dimensional model based on finite difference approximations

Charles R. Faust; James W. Mercer; Stephen D. Thomas; W. Pete Balleau

1984-01-01

198

Application of the computer code TOUGH2 to the simulation of supercritical conditions in geothermal systems  

Microsoft Academic Search

At the high pressures and temperatures found in deep geothermal systems, supercritical conditions can occur. Current numerical geothermal simulators are either not capable of modelling these conditions, or can do so only at significantly reduced computation speed. This paper describes modifications to the TOUGH2 simulator to extend its applicability. It employs the updated IAPWS-97 thermodynamic formulation, and uses density and

Adrian E. Croucher; Michael J. O’Sullivan

2008-01-01

199

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

200

Thermal Energy Recovery from Enhanced Geothermal Systems - Evaluating the Potential from Deep, High-Temperature Resources  

Microsoft Academic Search

Enhanced Geothermal Systems (EGS) are geothermal reservoirs that require some form of stimulation to develop the permeability necessary for the circulation of hot water and the recovery of heat for electric power generation. A variety of mechanical, chemical and thermal approaches to reservoir stimulation have been proposed and tested over more than three decades of research on EGS technology, with

C. Williams

2009-01-01

201

Comparing FRACHEM and SHEMAT for the modelling of brine-rock interactions in Enhanced Geothermal Systems  

Microsoft Academic Search

Coupled numerical simulations of heat transfer, fluid flow and chemical reactions in geothermal systems are complex because of the highly heterogeneous geology, high temperatures, elevated pressures and often high salinity of the formation fluids. Codes such as FRACHEM and SHEMAT have been developed to forecast the long-term evolution of exploited geothermal reservoirs in order to determine how fluid circulation within

Portier Sandrine; Kühn Michael; Vuataz François-David

202

Toward More Efficient Heat Mining: A Planned Enhanced Geothermal System Demonstration Project  

Microsoft Academic Search

We describe plans for a project of about 12-months duration to demonstrate new technology aimed at lowering the cost of an Engineered Geothermal System (EGS). An EGS creates or enhances a geothermal reservoir by stimulating fractures in hot rock, and then cycles water through the fractures to mine the in-place heat. The goal of the project is to create multiple

S. Petty; J. Iovenitti; R. Baria; T. Cladouhos; O. Callahan; A. Jupe; R. Adair

2008-01-01

203

GEOTHERMAL SYSTEMS ASSESSMENT—IDENTIFICATION AND MITIGATION OF EGS EXPLORATION RISK  

Microsoft Academic Search

The conventional view in Australia (and many other places) is that achieving optimal temperature is the critical risk in exploration for conductive geothermal resources. This view has often resulted in other areas of risk being overlooked. A Geothermal Systems Assessment (GSA) investigates and ranks four largely independent critical risk areas—heat source, thermal\\/hydraulic insulation, reservoir potential, and working fluid. These four

Graeme R Beardsmore; Gareth T Cooper

204

3D Velocity Tomographic Study of the Larderello Geothermal System, Tuscany Italy  

Microsoft Academic Search

The steam-dominated geothermal system of Larderello is located in Tuscany and is the largest Italian area of electricity generation from geothermal resources. Enel Green Power, the company of the ENEL Group involved in the renewable resources development, has drilled several wells down to maximum depth of about 4.0 km below see level in order to exploit deep and hot steam

R. de Matteis; T. Vanorio; B. Ciulli; E. Spinelli; A. Fiordelisi; A. Zollo

2003-01-01

205

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

SciTech Connect

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 patterns in the vicinity of hot springs as well as gross identification of dominant plant and mineral species. Spectra used for the classifications come from a vegetation spectral library created for plant species found to be associated with geothermal processes. This library takes into account the seasonality of vegetation by including spectra for species on a monthly basis. Geological spectra are taken from JPL and USGS mineral libraries. Preliminary classifications of hot spring areas indicate some success in mineral identification and less successful vegetation species identification. The small spatial extent of individual plants demands either sub-pixel analysis or increased spatial resolution of imagery. Future work will also include preliminary analysis of a hyperspectral thermal imagery dataset and a multitemporal air photo dataset. The combination of these remotely sensed datasets for Long Valley will yield a valuable product for geothermal exploration efforts in other regions.

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

1998-12-01

206

Raytheon Downhole Information System: Electromagnetic lithospheric information system for geothermal drilling. Interim report  

Microsoft Academic Search

The Raytheon Downhole Information System (RDIS), which is designed to reduce the drilling cost and increase the energy yield of deep geothermal wells, is described. The RDIS consists of a downhole sensor package located just above the drill bit, a telemetry link in the drill string, and a well head data management and control system. The RDIS assists the driller

M. Kolker; A. H. Greene; J. C. Robertson; M. D. Grossi

1977-01-01

207

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

208

Phase relations and adiabats in boiling seafloor geothermal systems  

NASA Astrophysics Data System (ADS)

Observations of large salinity variations and vent temperatures in the range of 380-400°C suggest that boiling or two-phase separation may be occurring in some seafloor geothermal systems. Consideration of flow rates and the relatively small differences in density between vapors and liquids at the supercritical pressures at depth in these systems suggests that boiling is occurring under closed-system conditions. Salinity and temperature of boiling vents can be used to estimate the pressure-temperature point in the subsurface at which liquid seawater first reached the two-phase boundary. Data are reviewed to construct phase diagrams of coexisting brines and vapors in the two-phase region at pressures corresponding to those of the seafloor geothermal systems. A method is developed for calculating the enthalpy and entropy of the coexisting mixtures, and results are used to construct adiabats from the seafloor to the P-T two-phase boundary. Results for seafloor vents discharging at 2300 m below sea level indicate that a 385°C vent is composed of a brine (7% NaCl equivalent) in equilibrium with a vapor (0.1% NaCl). Brine constitutes 45% by weight of the mixture, and the fluid first boiled at approximately 1 km below the seafloor at 415°C, 330 bar. A 400°C vent is primarily vapor (88 wt.%, 0.044% NaCl) with a small amount of brine (26% NaCl) and first boiled at 2.9 km below the seafloor at 500°C, 520 bar. These results show that adiabatic decompression in the two-phase region results in dramatic cooling of the fluid mixture when there is a large fraction of vapor.

Bischoff, James L.; Pitzer, Kenneth S.

1985-11-01

209

Phase relations and adiabats in boiling seafloor geothermal systems  

USGS Publications Warehouse

Observations of large salinity variations and vent temperatures in the range of 380-400??C suggest that boiling or two-phase separation may be occurring in some seafloor geothermal systems. Consideration of flow rates and the relatively small differences in density between vapors and liquids at the supercritical pressures at depth in these systems suggests that boiling is occurring under closed-system conditions. Salinity and temperature of boiling vents can be used to estimate the pressure-temperature point in the subsurface at which liquid seawater first reached the two-phase boundary. Data are reviewed to construct phase diagrams of coexisting brines and vapors in the two-phase region at pressures corresponding to those of the seafloor geothermal systems. A method is developed for calculating the enthalpy and entropy of the coexisting mixtures, and results are used to construct adiabats from the seafloor to the P-T two-phase boundary. Results for seafloor vents discharging at 2300 m below sea level indicate that a 385??C vent is composed of a brine (7% NaCl equivalent) in equilibrium with a vapor (0.1% NaCl). Brine constitutes 45% by weight of the mixture, and the fluid first boiled at approximately 1 km below the seafloor at 415??C, 330 bar. A 400??C vent is primarily vapor (88 wt.%, 0.044% NaCl) with a small amount of brine (26% NaCl) and first boiled at 2.9 km below the seafloor at 500??C, 520 bar. These results show that adiabatic decompression in the two-phase region results in dramatic cooling of the fluid mixture when there is a large fraction of vapor. ?? 1985.

Bischoff, J. L.; Pitzer, K. S.

1985-01-01

210

Geothermal activity in the subglacial Katla caldera, Iceland, 1999-2005, studied with radar altimetry  

NASA Astrophysics Data System (ADS)

The Katla caldera is located under the Mýrdalsjökull ice cap and is one of the most hazardous volcanoes in Iceland due to major jökulhlaups that accompany eruptions. Subglacial geothermal activity is manifested in several 10-50 m deep depressions (ice cauldrons) within and at the caldera rim and the total geothermal heat output is of the order of a few hundred megawatts. A shortlived but powerful pulse in geothermal heat output took place in 1999, probably including a minor subglacial eruption, when new ice cauldrons formed in three places and an unexpected jökulhlaup occurred. Following these events, a comprehensive monitoring program was set up for Katla, including ice surface elevation profiling from aircraft, to monitor variations in geothermal heat and detect signs of subglacial water accumulation. A radar altimeter coupled with a kinematic GPS is used, achieving an absolute elevation accuracy of 3 m and internal consistency of 1-2 m. Profiles across the caldera are flown twice a year. An annual accumulation-ablation cycle in surface elevation with amplitude of 5-10 m is observed. By removing this cycle from the data, changes due to subglacial geothermal activity are obtained. After the events in 1999, a decline in geothermal activity was observed. In 2001-03 some ice cauldrons expanded and deepened by 10-15 m, indicating renewed increase in geothermal activity. This trend is also apparent for 2003-05. The increase in geothermal poweramounts to a few tens of megawatts. It is likely that the increased thermal output is related to increased seismicity and caused by magma inflow.

Gu?mundsson, Magnús T.; Höganadóttir, Pórdís; Kristinsson, Arnór Bergur; Gu?björnsson, Snaebjörn

211

LAPA - a graphical analysis technique for prioritizing geothermal leasing activities on public lands  

SciTech Connect

This paper describes the development of a composite indicator for prioritizing geothermal leasing activities on public lands. LAPA utilizes fuzzy set software developed by the GRAD/SEEDIS projects at the Lawrence Berkeley Laboratory. It is an automated procedure which allows the analyst to use subjective categories to prioritize geothermal areas according to their unleased energy potential, the level of private response, and the potential for pre-lease environmental delays.

Yen, W.W.S.; Benson, W.H.

1982-10-01

212

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

213

Solar, Geothermal, Electric and Storage Systems Program Summary Document, FY 1979.  

National Technical Information Service (NTIS)

Attention is focused on the current and planned programs in: solar technology, geothermal energy development, low-head hydroelectric power development, electric energy systems, and energy storage systems. After setting forth national energy policy with re...

1978-01-01

214

Strategies for Detecting Hidden Geothermal Systems by Near-Surface Gas Monitoring  

Microsoft Academic Search

''Hidden'' geothermal systems are those systems above which hydrothermal surface features (e.g., hot springs, fumaroles, elevated ground temperatures, hydrothermal alteration) are lacking. Emissions of moderate to low solubility gases (e.g., CO2, CH4, He) may be one of the primary near-surface signals from these systems. Detection of anomalous gas emissions related to hidden geothermal systems may therefore be an important tool

Jennifer L. Lewicki; Curtis M. Oldenburg

2004-01-01

215

Three-dimensional imaging of a geothermal system using temperature and geological models derived from a well-log dataset  

Microsoft Academic Search

The accurate imaging of geothermal systems from the ground surface down to great depths is an interdisciplinary problem common to geothermal resource exploration and development. Rocks can be characterized mainly in terms of their lithology, mineralogy, fracture distribution, permeability, thermal conductivity and porosity, and similarly the geothermal fluid (and its circulation) by its geochemistry, flow pattern, velocity, temperature and pressure.

Yun Teng; Katsuaki Koike

2007-01-01

216

Design of an isobutane binary cycle geothermal generation system  

Microsoft Academic Search

A 1000-kW binary cycle geothermal power plant with isobutane as the working medium, which uses geothermal steam and hot water, was successfully run for the first time at Otake, Kyushu, in 1978. The paper discusses the development of this plant, the features of the Otake pilot plant, the outline of the plant, and the main components. The technological feasibility of

K. Aikawa

1980-01-01

217

CALCITE PRECIPITATION IN LOW TEMPERATURE GEOTHERMAL SYSTEMS: AN EXPERIMENTAL APPROACH  

Microsoft Academic Search

One of the most common production problems in geothermal fields is calcite (calcium carbonate) scale deposition. Calcite formed in the wellbore and in near wellbore region significantly decreases the output of a production well. Calcite scaling is experienced in almost all the geothermal fields around the world. Calcite may form from hydrolysis, boiling and heating of cooler peripheral fluids. Although

Omer Izgec; Birol Demiral; Henri Bertin; Serhat Akin

218

Stress corrosion cracking of stainless steels in geothermal systems  

Microsoft Academic Search

A failure analysis was made with an austenitic stainless steel, YUS 170, pipe installed close to a flush tank of the field exposure test apparatus at Onikobe geothermal wells in Japan. The pipe eventually experienced severe leakage of geothermal fluids from the top side of the laid pipe within 2 weeks operation. The cracks initiated underneath thick deposits and propagated

T. Murata; E. Sato; Y. Hosoi

1982-01-01

219

Enhanced Geothermal Systems Technology Phase II, Animas Valley, New Mexico.  

National Technical Information Service (NTIS)

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 Mex...

R. A. Cunniff R. L. Bowers

2003-01-01

220

Prospect of enhanced geothermal system in baseload power generation  

Microsoft Academic Search

Given the strength of commodity prices in recent years, concerns over energy security and widening adoption of carbon emission pricing, renewables are well positioned to play growing role in global energy mix. Geothermal energy is on the face of it. By harnessing the heat of the earth, geothermal power plants tap into a virtually inexhaustible and continuous source of energy,

M. R. Azim; M. S. Amin; M. A. Shoeb

2010-01-01

221

EXCEPTIONAL ENHANCED GEOTHERMAL SYSTEMS FROM OIL AND GAS RESERVOIRS  

Microsoft Academic Search

A lot of oil and gas reservoirs have been or will be abandoned in petroleum industry. In this study, we pointed out that these oil and gas reservoirs might be transferred into exceptional enhanced geothermal reservoirs with very high temperatures by oxidizing the residual oil with injected air. A concept to generate power from these exceptional enhanced geothermal reservoirs by

Kewen Li; Lingyu Zhang

222

Tectonic framework of hydrothermal and geothermal systems in the Menderes Massif, western Turkey  

NASA Astrophysics Data System (ADS)

The Menderes Massif in western Turkey lies at the eastern margin of the Hellenic subduction zone's continental backarc. Substantial hydrothermal alteration and geothermal activity have accompanied Miocene to recent extensional tectonics. Here we propose that the locations of Cenozoic magmatic, hydrothermal and geothermal activity are controlled by structures that formed to accommodate an overall E-W gradient in the magnitude of continental extension. We present data that demonstrate the close spatial relationship between Miocene transtensional deformation, magmatism, tectonic denudation, and the location of mineral deposits and geothermal fields. The Menderes Massif is part of the Tauride block, a distinct lithospheric province within the Alpine orogenic belt in western Turkey. Alpine contraction occurred from Cretaceous to Palaeogene during N - S convergence, including subduction of the Vardar-Izmir and the Pindos oceans and the collision of adjacent continental fragments with the Tauride block. Pre-Alpine basement rocks are predominantly late Proterozoic to Cambrian (‘Pan-African') in age, while basement rocks along strike in the Aegean Sea area are generally of Carboniferous age. While the nature of this boundary between the Pan-African and Carboniferous crustal domains is not clear, a significant difference exists in their geodynamic history. Whereas early in the Miocene the Hellenic subduction zone began to retreat in the Aegean Sea area, this apparently did not happen in western Turkey. Instead there is evidence for a tear in the slab that causes a thermal anomaly in the lithosphere. Miocene to recent extension in the Menderes Massif has led to the formation of metamorphic core complexes, NE-striking basins and a series of large E-W trending graben. These structures accommodate the overall sinistral strike-slip deformation forced by the slab retreat in the Aegean Sea region. The Menderes Massif hosts a variety of hydrothermal mineral deposits, including gold, copper, antimony, uranium and mercury. While there is evidence for gold mineralisation during crustal shortening, most other deposit types including epithermal gold, detachment gold, mercury, and sandstone-hosted uranium formed during the Miocene to recent crustal extension. Alteration of basement rocks and Cenozoic volcanic and sedimentary sequences is common in both fossil hydrothermal systems and geothermal fields. Hydrothermal activity is structurally controlled, and has predominantly occured along structures related to the formation of E-W graben. In addition to the involvement of meteoric fluids a mantle component has been shown. The apparent continuity in tectonic boundary conditions in the Menderes Massif since the Miocene, and the ongoing hydrothermal activity provide important insights into the structural control on hydrothermal mineral systems within or near continental backarcs.

Gessner, Klaus; Porwal, Alok; Markwitz, Vanessa; Wedin, Francis

2010-05-01

223

Characterization of a deep geothermal reservoir in an active volcanic area  

NASA Astrophysics Data System (ADS)

In this study an integrated methodological approach to characterize a complex deep geothermal reservoir located in an active volcanic setting in Indonesia is presented. The methods applied include hydraulic and hydrogeochemical (incl. isotope tracer) techniques to model groundwater flow, heat transport, and hydro-geochemical properties of the reservoir. 3D geological and hydraulic models of the area were constructed based on deep drill profiles, collected fluid and rock samples, and mapping of geological structures. First results show that the geothermal reservoir is composed of major geological units such as altered andesite, basalt, breccia, and tuff layers. Several tectonic faults crosscut the geological units into individual blocks and reservoirs and influence hydraulic pathways in multiple ways. Hot water and steam are produced by nine wells. Fluids are reinjected into the reservoir through one injection well. Currently, a geothermal plant produces 60 MWe from steam withdrawn. Temperatures of the geothermal system range between 250 and 350 °C (Koestono et al. 2010). Based on the chemical composition of fluids from the production wells (concentration of major ions and physicochemical parameters) at least two different hydro-geochemical reservoirs could be identified. The deep reservoir with a moderate pH of 5 is marked by total silica concentrations up to 350 mg/L and high chloride concentrations of 430 mg/L. For the shallow reservoir, highly acidic conditions with pH values of 2.9 are analysed for water, while steam shows pH values around 4. Furthermore, high chloride (1550 mg/L), total silica (460 mg/L), and sulphate concentrations (1600 mg/L) are characteristic for the shallow reservoir. According to Giggenbach (1988) and Nicholson (1993) the water can be classified into sulphate-rich waters and neutral chloride-waters. Sulphate-rich water is expected to occur near to the heat source while chloride-rich waters discharge near the outflow zone. Surface reservoirs, e.g. an acid lake and several hot springs seem to be in close contact with the shallow reservoir.

Brehme, M.; Kamah, Y.; Koestono, H.; Zimmermann, G.; Regenspurg, S.; Erba?, K.; Wiegand, B.; Sauter, M.

2012-04-01

224

Geopressured-geothermal well activities in Louisiana. Annual report, 1 January 1991--31 December 1991  

SciTech Connect

Since September 1978, microseismic networks have operated continuously around US Department of Energy (DOE) geopressured-geothermal well sites to monitor any microearthquake activity in the well vicinity. Microseismic monitoring is necessary before flow testing at a well site to establish the level of local background seismicity. Once flow testing has begun, well development may affect ground elevations and/or may activate growth faults, which are characteristic of the coastal region of southern Louisiana and southeastern Texas where these geopressured-geothermal wells are located. The microseismic networks are designed to detest small-scale local earthquakes indicative of such fault activation. Even after flow testing has ceased, monitoring continues to assess any microearthquake activity delayed by the time dependence of stress migration within the earth. Current monitoring shows no microseismicity in the geopressured-geothermal prospect areas before, during, or after flow testing.

John, C.J.

1992-10-01

225

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

226

Locating an active fault zone in Coso geothermal field by analyzing seismic guided waves from microearthquake data  

SciTech Connect

Active fault systems usually provide high-permeability channels for hydrothermal outflow in geothermal fields. Locating such fault systems is of a vital importance to plan geothermal production and injection drilling, since an active fault zone often acts as a fracture-extensive low-velocity wave guide to seismic waves. We have located an active fault zone in the Coso geothermal field, California, by identifying and analyzing a fault-zone trapped Rayleigh-type guided wave from microearthquake data. The wavelet transform is employed to characterize guided-wave's velocity-frequency dispersion, and numerical methods are used to simulate the guided-wave propagation. The modeling calculation suggests that the fault zone is {approx} 200m wide, and has a P wave velocity of 4.80 km/s and a S wave velocity of 3.00 km/s, which is sandwiched between two half spaces with relatively higher velocities (P wave velocity 5.60 km/s, and S wave velocity 3.20 km/s). zones having vertical or nearly vertical dipping fault planes.

SGP-TR-150-16

1995-01-26

227

Value analysis of advanced heat rejection systems for geothermal power plants  

Microsoft Academic Search

A computer model is developed to evaluate the performance of the binary geothermal power plants (Organic Rankine Cycles) with various heat rejection systems and their impact on the levelized cost of electricity.

Vahab Hassani

1996-01-01

228

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

229

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

230

Development of Models to Simulate Tracers Behavior in Enhanced Geothermal Systems.  

National Technical Information Service (NTIS)

A recent report found that power and heat produced from engineered (or enhanced) geothermal systems (EGSs) could have a major impact on the United States while incurring minimal environmental impacts. EGS resources differ from high-grade hydrothermal reso...

D. Newell M. D. Willimas P. W. Reimus T. Watson V. R. Vermeul

2010-01-01

231

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

232

Modeling Fluid Pressure and Permeability Evolution in Enhanced Geothermal Systems  

NASA Astrophysics Data System (ADS)

Enhanced geothermal systems use high-pressure fluids to open up permeable pathways between fluid injection wells and production wells, so it is essential to understand the dominant processes controlling the spatio-temporal evolution of the permeable network and the fluid pressure within the stimulated region. Most estimates of the fluid pressure field, and thus earthquake triggering pressures, and the hydraulic diffusivity of the stimulated region are based on simplified models of linear pressure diffusion from a spherical source. These estimates drastically underestimate the true fluid pressure and permeability because the dominant physical process controlling these systems is the large-scale increase in permeability coincident with triggered seismicity. I present the results of a minimalist model that captures the dominant processes operating at depth, and compare model results to all available data associated with the Basel enhanced geothermal experiment. Using the measured fluid-pressure time history as a boundary condition applied to the borehole, I numerically solve a 2D non-linear diffusion equation, where permeability is a function of the effective normal stress, and the initial permeability field is constrained by the measured effective permeability of reservoir (~10^-17m^2). In the model, permeability increases by a large factor (e.g. 1000-fold) when a region in the numerical domain reaches a Mohr-Coulomb failure condition for shear failure. Model results show that the average evolved fluid pressure field within the stimulated region reaches a maximum of about 10 MPa (at peak borehole pressure of ~30MPa), and a maximum permeability at peak pressure of about 5x10^-14 m^2, consistent with the measured permeability. Excellent comparisons between model and observations are obtained between earthquake rates, earthquake hypocenters, hypocenter migration, and flow rates. Because the model here is also a diffusion process, some similarities are seen with linear diffusion models, however, the fluid pressure and diffusivity in the stimulated region are orders of magnitude higher than that predicted by linear diffusion models. These results have major implications not only for the state of the stimulated region, but also about criticality in the crust and earthquake hazards associated with these systems.

Miller, S. A.

2011-12-01

233

Systems study of drilling for installation of geothermal heat pumps  

SciTech Connect

Geothermal, or ground-source, heat pumps (GHP) are much more efficient than air-source units such as conventional air conditioners. A major obstacle to their use is the relatively high initial cost of installing the heat-exchange loops into the ground. In an effort to identify drivers which influence installation cost, a number of site visits were made during 1996 to assess the state-of-the-art in drilling for GHP loop installation. As an aid to quantifying the effect of various drilling-process improvements, we constructed a spread-sheet based on estimated time and material costs for all the activities required in a typical loop-field installation. By substituting different (improved) values into specific activity costs, the effect on total project costs can be easily seen. This report contains brief descriptions of the site visits, key points learned during the visits, copies of the spread-sheet, recommendations for further work, and sample results from sensitivity analysis using the spread-sheet.

Finger, J.T.; Sullivan, W.N.; Jacobson, R.D.; Pierce, K.G.

1997-09-01

234

Federal Geothermal Research Program Update Fiscal Year 2004  

SciTech Connect

The Department of Energy (DOE) and its predecessors have conducted research and development (R&D) in geothermal energy since 1971. The Geothermal Technologies Program (GTP) works in partnership with industry to establish geothermal energy as an economically competitive contributor to the U.S. energy supply. Geothermal energy production, a $1.5 billion a year industry, generates electricity or provides heat for direct use applications. The technologies developed by the Geothermal Technologies Program will provide the Nation with new sources of electricity that are highly reliable and cost competitive and do not add to America's air pollution or the emission of greenhouse gases. Geothermal electricity generation is not subject to fuel price volatility and supply disruptions from changes in global energy markets. Geothermal energy systems use a domestic and renewable source of energy. The Geothermal Technologies Program develops innovative technologies to find, access, and use the Nation's geothermal resources. These efforts include emphasis on Enhanced Geothermal Systems (EGS) with continued R&D on geophysical and geochemical exploration technologies, improved drilling systems, and more efficient heat exchangers and condensers. The Geothermal Technologies Program is balanced between short-term goals of greater interest to industry, and long-term goals of importance to national energy interests. The program's research and development activities are expected to increase the number of new domestic geothermal fields, increase the success rate of geothermal well drilling, and reduce the costs of constructing and operating geothermal power plants. These improvements will increase the quantity of economically viable geothermal resources, leading in turn to an increased number of geothermal power facilities serving more energy demand. These new geothermal projects will take advantage of geothermal resources in locations where development is not currently possible or economical.

Not Available

2005-03-01

235

Federal Geothermal Research Program Update - Fiscal Year 2004  

SciTech Connect

The Department of Energy (DOE) and its predecessors have conducted research and development (R&D) in geothermal energy since 1971. The Geothermal Technologies Program (GTP) works in partnership with industry to establish geothermal energy as an economically competitive contributor to the U.S. energy supply. Geothermal energy production, a $1.5 billion a year industry, generates electricity or provides heat for direct use applications. The technologies developed by the Geothermal Technologies Program will provide the Nation with new sources of electricity that are highly reliable and cost competitive and do not add to America's air pollution or the emission of greenhouse gases. Geothermal electricity generation is not subject to fuel price volatility and supply disruptions from changes in global energy markets. Geothermal energy systems use a domestic and renewable source of energy. The Geothermal Technologies Program develops innovative technologies to find, access, and use the Nation's geothermal resources. These efforts include emphasis on Enhanced Geothermal Systems (EGS) with continued R&D on geophysical and geochemical exploration technologies, improved drilling systems, and more efficient heat exchangers and condensers. The Geothermal Technologies Program is balanced between short-term goals of greater interest to industry, and long-term goals of importance to national energy interests. The program's research and development activities are expected to increase the number of new domestic geothermal fields, increase the success rate of geothermal well drilling, and reduce the costs of constructing and operating geothermal power plants. These improvements will increase the quantity of economically viable geothermal resources, leading in turn to an increased number of geothermal power facilities serving more energy demand. These new geothermal projects will take advantage of geothermal resources in locations where development is not currently possible or economical.

Patrick Laney

2005-03-01

236

Enhanced Geothermal Systems (EGS) R&D Program: Monitoring EGS-Related Research  

SciTech Connect

This report reviews technologies that could be applicable to Enhanced Geothermal Systems development. EGS covers the spectrum of geothermal resources from hydrothermal to hot dry rock. We monitored recent and ongoing research, as reported in the technical literature, that would be useful in expanding current and future geothermal fields. The literature review was supplemented by input obtained through contacts with researchers throughout the United States. Technologies are emerging that have exceptional promise for finding fractures in nonhomogeneous rock, especially during and after episodes of stimulation to enhance natural permeability.

McLarty, Lynn; Entingh, Daniel; Carwile, Clifton

2000-09-29

237

Hybrid Cooling Systems for Low-Temperature Geothermal Power Production  

Microsoft Academic Search

This paper describes the identification and evaluation of methods by which the net power output of an air-cooled geothermal power plant can be enhanced during hot ambient conditions with a minimal amount of water use.

A. Ashwood; D. Bharathan

2011-01-01

238

Hybrid Cooling Systems for Low-Temperature Geothermal Power Production  

SciTech Connect

This paper describes the identification and evaluation of methods by which the net power output of an air-cooled geothermal power plant can be enhanced during hot ambient conditions with a minimal amount of water use.

Ashwood, A.; Bharathan, D.

2011-03-01

239

Thermodynamic Analysis of Geothermal Power Systems Employing Separating Expanders.  

National Technical Information Service (NTIS)

A thermodynamic analysis was performed in order to study the possibility of upgrading the thermodynamic performance of a direct-steam geothermal power plant through the use of a separating expander which produces work while achieving effective separation ...

H. E. Khalifa E. Michaelides

1978-01-01

240

Enhanced Geothermal Systems (EGS) Well Construction Technology Evaluation Report.  

National Technical Information Service (NTIS)

Electricity production from geothermal resources is currently based on the exploitation of hydrothermal reservoirs. Hydrothermal reservoirs possess three ingredients critical to present day commercial extraction of subsurface heat: high temperature, in-si...

A. J. Mansure D. W. Raymond J. T. Finger L. Capuano M. Huh

2008-01-01

241

Developing and circulating a fault system in the crystalline rock for geothermal power generation in Insheim, Germany.  

NASA Astrophysics Data System (ADS)

Pfalzwerke geofuture GmbH together with its general contractor BESTEC GmbH intend to build a geothermal power plant in Insheim using a single fault system in the crystalline rock for geothermal heat extraction. The Insheim site is located in the Upper Rhine Graben, about 4 km South of the geothermal power plant in Landau, Germany, and about 30 km North of the European EGS site at Soultz-sous-Forêts, France. In 2008 and 2009 two wells were successfully drilled to a depth of about 3,800 meters targeting the same fault system in the crystalline basement. The geothermal reservoir was tapped with a temperature of more than 165 degrees Celsius. In order to improve well properties and prepare both wells for safe, clean and viable power generation, circulation tests and hydraulic injections with gradually increasing flowrate were conducted in late 2009 and early 2010. Seismic monitoring networks, recording also ground velocities, along with an alarm plan ensured the success of the operations. The recorded peak ground velocities stayed far below the reference values of 3 and 5 millimeters per second, specified in the DIN 4150, while seismic activity obviously decreased during the hydraulic operations. In autumn 2010 a lateral well was drilled out of the injection well at approximately 2,500 meters, aiming to better distribute the fluid volume between the two injection branches and thus further minimize microseismic activity. During subsequent hydraulic injection tests no more seismicity was registered. The geothermal power plant in Insheim will have a capacity of 4 to 5 megawatts, capable of supplying about 8,000 homes with electrical energy. The beginning of electric power production is planned for summer 2012.

Teza, D.; Baumgärtner, J.; Lerch, C.; Gandy, T.; Hettkamp, T.; Penzkofer, P.; Schindler, M.; Wahl, G.

2011-12-01

242

Experimental Study of Water Injection into Geothermal Systems  

Microsoft Academic Search

Water injection or reinjection in geothermal reservoirs has been proven as a successful engineering technique with many benefits\\u000a such as maintaining reservoir pressure and sustaining well productivity. However, many questions related to water injection\\u000a into geothermal reservoirs still remain unclear; for example, how the in-situ water saturation changes with reservoir pressure\\u000a and temperature, and how the reservoir pressure influences well

Kewen Li; Huda Nassori; Roland N. Horne

2010-01-01

243

The Moana geothermal system in Reno, Nevada: A hydrologic, geochemical, and thermal analysis  

SciTech Connect

The Moana geothermal systems, located in Reno, Nevada, is a moderate-temperature geothermal resource used for space heating applications. Both historic and new hydrologic, thermal, and groundwater chemistry data were collected to evaluate the Moana system and to develop a calibrated numerical model of the geothermal aquifer for investigation of resource development scenarios. The new data collection consisted of static water level measurements and temperature with depth measurements for a 13-month period at 26 geothermal wells to investigate hydrologic and thermal changes with time. In addition, groundwater chemistry sampling at 10 wells was used to evaluate mixing of thermal and nonthermal waters. Collected information indicates that in the most heavily used portion of the geothermal aquifer, the hydraulic heads have declined. This decline may induce additional leakage of cooler water from the overlying unconfined aquifer and lead to decreased temperatures at well locations in the geothermal aquifer. The groundwater chemistry data show concentration changes with temperature for boron, chloride, fluoride, lithium, and bicarbonate that are a function of the degree of mixing of thermal and nonthermal waters. Temporal changes in these constituents may be used as an indication of relative temperature changes in the geothermal system caused by mixing at a given location. An attempt was made to use the hydraulic head and maximum temperature data to develop a calibrated numerical model for the Moana geothermal system. However, lack of information about the horizontal and vertical thermal and fluid fluxes made the development of a calibrated model not possible at this time. 25 refs., 54 figs., 6 tabs.

Jacobson, E.A.; Johnston, J.W.

1991-03-01

244

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

Microsoft Academic Search

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

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

2010-01-01

245

Evaluation of Oil-Industry Stimulation Practices for Engineered Geothermal Systems  

Microsoft Academic Search

Geothermal energy extraction is typically achieved by use of long open-hole intervals in an attempt to connect the well with;\\u000athe greatest possible rock mass. This presents a problem for the development of Enhanced (Engineered) Geothermal;\\u000aSystems (EGS), owing to the challenge of obtaining uniform stimulation throughout the open-hole interval. Fluids are often;\\u000ainjected in only a fraction of that

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

2007-01-01

246

The geothermal program at Lawrence Berkeley Laboratory  

SciTech Connect

The main purpose of the geothermal program at Lawrence Berkeley Laboratory is to develop, improve and validate methods and instrumentation to: (1) determine geothermal reservoir parameters; (2) detect and characterize reservoir fractures and boundaries; and (3) identify and evaluate the importance of reservoir processes. The ultimate objective of the program, which includes field, theoretical and modeling activities, is to advance the state-of-the-art for characterizing geothermal systems and evaluating their productive capacity and longevity under commercial exploitation.

Lippmann, M.J.

1987-06-01

247

Water-rock interaction in a zone of lateral flow: A natural example from the active geothermal field and gold-mineralized zone of Beppu (Kyushu Island, Japan)  

Microsoft Academic Search

Summary Beppu is a water-dominated active geothermal system in Kyushu (Japan). Gold mineralization exists in places within altered Pleistocene volcanites in the southernmost part of this field. A shallow 300 m well was drilled in an alluvial fan deposit made up of unsorted volcanic clasts of andesite and dacite. Water and core samples were collected and a temperature log was

G. Gianelli; Y. Yusa; S. Battaglia; K. Takemura

1992-01-01

248

Geothermic activity and seismotectonics in the altitude of the Tibetan plateau  

NASA Astrophysics Data System (ADS)

In the present analysis on the relationships among the depth of lithosphere brittle fracture, seismotectonics and geothermal anomalous active in Tibetan plateau were investigated using the seismic dada from ISC and Chinese seismic net and geothermal data. The results suggest that the region of anomalously geothermal activity almost coincides with that of the normal faulting type earthquake. The geothermal anomaly activity region coincides spatially with that of the events deeper than 60 km as well as. The normal faulting earthquakes may be mainly tectonic activity regimes until 110 km deep in the thermal anomaly region. The strike directions of events are likely the N-S direction, coinciding with the strike of the thermal anomaly active belts. The earthquakes align along the normal faults and faulted-depression zone with the N-S direction. The thermal anomaly activity also distributes along the faulted-depression zone. Many events deeper than 60 km exist in the anomalously geothermal activity region in the plateau. Events extend to bottom of the lithosphere of 110 km from the surface, like columnar seismic crowd. The lithosphere extends along the E-W direction due to the E-W extensional stress in the central and southern Tibetan plateau, altitude of the plateau. The tensional stress in the E-W results in the lithosphere fractures and the normal faults striking N-S direction, grabens and faulted-depression zones. Thermal material from the asthenosphere wells upward to the surface along deep seismic fractures and faults through the thick crust. The anomalously thermal activities are attributable to the upwelling thermal material from the mantle in the altitude of Tibetan plateau.

Xu, Jiren; Zhao, Zhixin

2009-12-01

249

Geothermal energy control system and method. [downhole turbine-driven pump system  

Microsoft Academic Search

A geothermal energy transfer and utilization system makes use of thermal energy stored in hot solute-bearing well water to generate superheated steam from an injected flow of clean water; the superheated steam is then used for operating a turbine-driven pump at the well bottom for pumping the hot solute-bearing water at high pressure and in liquid state to the earth's

1977-01-01

250

Investigation of hydrogeochemical properties of the Hüdai (Afyon-Sand?kl?) geothermal systems, SW Turkey  

NASA Astrophysics Data System (ADS)

Sand?kl?-Hüdai geothermal field is one of the geothermal systems in Afyon and environ, located approximately 40 km southwest of Afyon. The study area consists of volcanic, sedimentary and metamorphic rocks. Kestel greenschist formation of Paleozoic age forms the basement rock in the area while quartzite which is a member of the Kestel greenschist formation serves as the reservoir rock of Sand?kl?-Hüdai geothermal system. Geothermal waters from the study area are classified as Na-SO4-HCO3 type waters. The waters plot along SO4-HCO3 end of the Cl-SO4-HCO3 triangle diagram suggesting same origin for the geothermal waters. ? 18O and ?D isotope ratios of the Sand?kl? waters plot along the continental meteoric water line, indicating meteoric waters that were unaffected by evaporation. The tritium values imply that the fluids were deep circulating and recharged from older waters. Furthermore, oversaturation of the geothermal fluids with quartz confirms these findings showing long time residence of these groundwaters.

Demer, Selma (Altinkale); Memi?, Ümit; Özgür, Nevzat

2013-08-01

251

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

252

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

253

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

254

New Mexican geothermal development  

SciTech Connect

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 development. In 1980, the state initiated the Geothermal Commercialization Program. The program's goal is to promote the use of geothermal energy for economic development. The primary target is the sector of the commercial greenhouse industry growing high-value horticultural and floricultural crops. New Mexico State University (NMSU) has become the center of the state's geothermal research program. The NMSU Geothermal Greenhouse Facility, constructed and operated by the New Mexico Solar Energy Institute, is a 12,000-square-foot, geothermally-heated greenhouse that provides a testing facility for commercial growers considering southern New Mexico for their operations. By 1985, the state's geothermal greenhouse industry covered 13 acres. Since the NMSU greenhouses were constructed in 1986, two large greenhouse companies have taken advantage of the facilities. Flores de New Mexico, of Las Cruces, and Masson Southwest, Inc. of Linwood, Kansas, used the facilities for pilot studies of the area. Both have stayed in the area and have expanded. Flores de New Mexico built 10 acres of greenhouses on the NMSU campus and is planning a five-acre expansion, and Masson, Inc. is building a four-acre greenhouse in Radium Springs, NM. Geothermal technology is also being used by three greenhouse businesses in Hidalgo County's Animas Valley, south of Lordsburg. Beall Company of New Mexico, Inc., Burgett Floral, Inc., and McCant's Greenhouse are tapping into the large thermal reservoir in the southwestern corner of the state.

Gerard, V.

1987-06-01

255

Strategies for Detecting Hidden Geothermal Systems by Near-Surface Gas Monitoring  

SciTech Connect

''Hidden'' geothermal systems are those systems above which hydrothermal surface features (e.g., hot springs, fumaroles, elevated ground temperatures, hydrothermal alteration) are lacking. Emissions of moderate to low solubility gases (e.g., CO2, CH4, He) may be one of the primary near-surface signals from these systems. Detection of anomalous gas emissions related to hidden geothermal systems may therefore be an important tool to discover new geothermal resources. This study investigates the potential for CO2 detection and monitoring in the subsurface and above ground in the near-surface environment to serve as a tool to discover hidden geothermal systems. We focus the investigation on CO2 due to (1) its abundance in geothermal systems, (2) its moderate solubility in water, and (3) the wide range of technologies available to monitor CO2 in the near-surface environment. However, monitoring in the near-surface environment for CO2 derived from hidden geothermal reservoirs is complicated by the large variation in CO2 fluxes and concentrations arising from natural biological and hydrologic processes. In the near-surface environment, the flow and transport of CO2 at high concentrations will be controlled by its high density, low viscosity, and high solubility in water relative to air. Numerical simulations of CO2 migration show that CO2 concentrations can reach very high levels in the shallow subsurface even for relatively low geothermal source CO2 fluxes. However, once CO2 seeps out of the ground into the atmospheric surface layer, surface winds are effective at dispersing CO2 seepage. In natural ecological systems in the absence of geothermal gas emissions, near-surface CO2 fluxes and concentrations are primarily controlled by CO2 uptake by photosynthesis, production by root respiration, and microbial decomposition of soil/subsoil organic matter, groundwater degassing, and exchange with the atmosphere. Available technologies for monitoring CO2 in the near-surface environment include (1) the infrared gas analyzer (IRGA) for measurement of concentrations at point locations, (2) the accumulation chamber (AC) method for measuring soil CO2 fluxes at point locations, (3) the eddy covariance (EC) method for measuring net CO2 flux over a given area, (4) hyperspectral imaging of vegetative stress resulting from elevated CO2 concentrations, and (5) light detection and ranging (LIDAR) that can measure CO2 concentrations over an integrated path. Technologies currently in developmental stages that have the potential to be used for CO2 monitoring include tunable lasers for long distance integrated concentration measurements and micro-electronic mechanical systems (MEMS) that can make widespread point measurements. To address the challenge of detecting potentially small-magnitude geothermal CO2 emissions within the natural background variability of CO2, we propose an approach that integrates available detection and monitoring methodologies with statistical analysis and modeling strategies. Within the area targeted for geothermal exploration, point measurements of soil CO2 fluxes and concentrations using the AC method and a portable IRGA, respectively, and measurements of net surface flux using EC should be made. Also, the natural spatial and temporal variability of surface CO2 fluxes and subsurface CO2 concentrations should be quantified within a background area with similar geologic, climatic, and ecosystem characteristics to the area targeted for geothermal exploration. Statistical analyses of data collected from both areas should be used to guide sampling strategy, discern spatial patterns that may be indicative of geothermal CO2 emissions, and assess the presence (or absence) of geothermal CO2 within the natural background variability with a desired confidence level. Once measured CO2 concentrations and fluxes have been determined to be of anomalous geothermal origin with high confidence, more expensive vertical subsurface gas sampling and chemical and isotopic analyses can be undertaken. Integrated analysis of all measurements will d

Lewicki, Jennifer L.; Oldenburg, Curtis M.

2004-12-15

256

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

257

Geothermal rotary separator turbine: wellhead power system tests at Milford, Utah  

Microsoft Academic Search

Through development of a separator\\/expander engine EPRI is improving the efficiency of single flash geothermal power systems. Under cost-shared contracts with Biphase Energy Systems and Utah Power and Light Company (UP and L), a wellhead power generating system has been built and tested. The wellhead unit has been operated for 4000 hours at Roosevelt Hot Springs near Milford, Utah. Phillips

1983-01-01

258

Development of a Distributed Control System (DCS) for Geothermal Steamfield Operations at Kawerau, NZ  

SciTech Connect

A distributed control system (DCS) has been developed for operation of the Kawerau geothermal field. The DCS functions include steam pressure control, steam flow billing, flow and pressure monitoring, remote well flow control and auto paging field operators. The system has evolved over a number of years from paper chart recorders to dataloggers to a desktop PC system to an industrial DCS.

Koorey, K.J.

1995-01-01

259

The Design of Large Geothermally Powered Air-Conditioning Systems Using an Optimal Control Approach  

Microsoft Academic Search

The direct use of geothermal energy from Hot Sedimentary Aquifer (HSA) systems for large scale air-conditioning projects involves many tradeoffs. Aspects contributing towards making design decisions for such systems include: the inadequately known permeability and thermal distributions underground; the combinatorial complexity of selecting pumping and chiller systems to match the underground conditions to the air-conditioning requirements; the future price variations

F. G. Horowitz; L. O'Bryan

2010-01-01

260

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

261

Natural convection in porous media and geothermal systems  

Microsoft Academic Search

Experimental and theoretical results concerning the natural and mixed convection in homogeneous and isotropic porous layers saturated with fluid are presented. A description of a sophisticated model used in the analysis of the physical observations on heat transfer is given. Attention is also given to the case where the porous medium is not isotropic. The role of convection in geothermal

M. Combarnous

1978-01-01

262

Thermodynamic analysis of geothermal power systems employing separating expanders  

Microsoft Academic Search

A thermodynamic analysis was performed in order to study the possibility of upgrading the thermodynamic performance of a direct-steam geothermal power plant through the use of a separating expander which produces work while achieving effective separation of the two phases. One such device is the Biphase rotary separator. Preliminary testing of this device demonstrated that the isentropic efficiency is about

H. E. Khalifa; E. Michaelides

1978-01-01

263

Enhanced Geothermal Systems (EGS) well construction technology evaluation report  

Microsoft Academic Search

Electricity production from geothermal resources is currently based on the exploitation of hydrothermal reservoirs. Hydrothermal reservoirs possess three ingredients critical to present day commercial extraction of subsurface heat: high temperature, in-situ fluid and high permeability. Relative to the total subsurface heat resource available, hydrothermal resources are geographically and quantitatively limited. A 2006 DOE sponsored study led by MIT entitled 'The

Capuano Louis Jr; Michael Huh; Robert Swanson; David Wayne Raymond; John Travis Finger; Arthur James Mansure; Yarom Polsky; Steven Dell Knudsen

2008-01-01

264

Design Considerations for Artificial Lifting of Enhanced Geothermal System Fluids  

Microsoft Academic Search

This work evaluates the effect of production well pumping requirements on power generation. The amount of work that can be extracted from a geothermal fluid and the rate at which this work is converted to power increase as the reservoir temperature increases. Artificial lifting is an important issue in this process. The results presented are based on a configuration comprising

Xina Xie; K. K. Bloomfield; G. L. Mines; G. M. Shook

2005-01-01

265

Seismic methods for resource exploration in enhanced geothermal systems  

Microsoft Academic Search

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

Roland Gritto; Ernest L. Majer

2002-01-01

266

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

267

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

268

3D Velocity Tomographic Study of the Larderello Geothermal System, Tuscany -Italy  

NASA Astrophysics Data System (ADS)

The steam-dominated geothermal system of Larderello is located in Tuscany and is the largest Italian area of electricity generation from geothermal resources. Enel Green Power, the company of the ENEL Group involved in the renewable resources development, has drilled several wells down to maximum depth of about 4.0 km below see level in order to exploit deep and hot steam reservoirs. In the explored area, about 400 km^2 wide, two steam-dominated reservoirs were tapped by wells at different depth. The shallowest one is hosted in very permeable carbonate formations at depth of about 1 km having pressure between 0.2 and 1.5 MPa and temperatures ranging between 150C and 260C. The deepest reservoir is located in the metamorphic basement up to depth of 3-4 km b.s.l. and is characterized by pressure of about 7.0 MPa and temperature ranging between 300 and 350C. Water reinjection is operating in the shallow reservoir of the geothermal area with the aim of both sustaining and increasing reservoir pressures as well as steam production. Main goals of this study have been both to determine reliable earthquakes locations in a detailed 3- D velocity model and to define deep structural features of the geothermal field. A high-resolution 3D-velocity model of subsurface structures was lacking for this area. Therefore, this research has been addressed to image the seismic velocity structures by 3D microearthquakes tomographic inversion. Enel Green Power continuously surveys the seismic activity in the Larderello area since 1977 by using a digital local network consisting of 26 seismic stations, three of which are three components. The analyzed data set consists of approximately 500 microearthquakes occurring from January 1994 through September 2000. The good quality of recorded waveforms allowed us for high precision readings of P- and S- wave first arrivals providing a total of about 5,000 P- and 2,500 S- arrival time readings. Results of 3D velocity tomographic inversion have shown both vertical and lateral variations in term of Vp and Vp/Vs ratio that have been correlated to the main geological features of the geothermal system. In particular a low P- velocity structure lies in the middle west of the investigated area from the surface up to 3km depth. At 3 km depth, the existence of a well constrained high velocity zone delineates the morphology of the metamorphic basement which is consistent with the emplacement of the deeper reservoir. Cross sections show that the top of the metamorphic basement uplifts up to 3-4 km in the central part of the area and dips towards SE up to 10 km. By correlation with gravity data, the recovered high velocity anomalies match quite well residual Bouguer gravity highs. Furthermore, earthquake locations in the 3- D velocity model are distributed within peculiar areas clustering by linear features along the thermo-metamorphic basement top up to 13 km. This might indicate either a regional stress zone or preferential fluid propagation paths into the fracture systems.

de Matteis, R.; Vanorio, T.; Ciulli, B.; Spinelli, E.; Fiordelisi, A.; Zollo, A.

2003-04-01

269

Modeling geothermal systems: A systematic investigation of permeability reduction under hydrothermal conditions  

NASA Astrophysics Data System (ADS)

Sustained geothermal energy production at economically viable levels requires maintaining permeability over time. However, active mineral precipitation can rapidly reduce the permeability of hydrothermal reservoirs. Since fractures typically provide the main conduits for fluid flow, understanding fracture evolution under hydrothermal conditions is crucial for the long-term utilization of geothermal systems. The interdependent nature of mechanisms controlling the hydrological and geochemical properties of these systems makes reactive transport models essential for predicting future reservoir behavior. However, a major challenge in utilizing these models is accurately quantifying the evolving physical and chemical states of the system. We address this challenge by modeling the evolution of fracture permeability due to mineral dissolution and precipitation in low porosity crystalline rocks under hydrothermal conditions. We evaluate the predictive abilities of our reactive transport models by comparing our calculations with the results of a series of flow-through laboratory experiments conducted on Westerly granite (Morrow et al., JGR, 106, B12, pp. 30551-30560, 2001). The initial permeability and temperature values used in our models range from 1.0×10-19 to 1.5×10-17 m2 and 150 to 300 °C, respectively. Starting material is assumed to be comprised of plagioclase (~40 vol.%), K-feldspar (~25 vol.%), quartz (~25 vol.%), and biotite (~6 vol.%). These values match the experimental conditions and are appropriate for Westerly granite. Simulations are further constrained by the requirement that final permeability, relative mineral abundances, and fluid chemistry agree with experimental observations. Changes in fracture permeability, porosity, mineral abundances, and solute concentrations are simulated over time for a range of starting fluid compositions, reactive surface areas, and rate constants. Starting fluid chemistry, reactive surface areas, and rate constants are systematically varied within the ranges of uncertainty. Either a cubic or modified cubic law is used for updating fracture permeability. We evaluate the manner in which each of the varied parameters controls the permeability. Some of the main alteration minerals predicted by our models include smectite, calcite, and K-feldspar. Abundances of the secondary minerals depend sensitively upon the initial conditions and vary between simulations. However, in all cases, we find that the precipitation of smectite is critical in determining the rate and sign of the permeability changes. Additionally, we observe that, in order to best match experimental output, overall reaction rates must be initially rapid but then quickly decrease with time in response to decreasing mineral accessibility. Given the importance of fractures in controlling fluid flow and the difficulty of testing reactive transport models in the field, the information provided by benchmarking these models against well-controlled laboratory experiments should provide more confidence in modeling the long-term evolution of large-scale geothermal systems.

Palguta, J.; Williams, C.; Ingebritsen, S.; Hickman, S.; Sonnenthal, E. L.

2010-12-01

270

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

271

Three-dimensional upper crustal structure of the geothermal system in Tarutung (North Sumatra, Indonesia) revealed by seismic attenuation tomography  

NASA Astrophysics Data System (ADS)

The geothermal potential in Tarutung is controlled by both the Sumatra Fault system and young arc volcanism. In this study we use the spatial distribution of seismic attenuation, calculated from local earthquake recordings, to image the 3-D seismic attenuation of the area and relate it with the temperature anomalies and the fluid distribution of the subsurface. A temporary seismic network of 42 stations was deployed around Tarutung and Sarulla (south of Tarutung) for a period of 10 months starting in 2011 May. Within this period, the network recorded 2586 local events. A high-quality subset of 229 events recorded by at least 10 stations was used for the attenuation inversion (tomography). Path-average attenuation (tp^{*}) was calculated by using a spectral inversion method. The spread function, the contour lines of the model resolution matrix and the recovery test results show that our 3-D attenuation model (Qp) has good resolution around the Tarutung Basin and along the Sarulla graben. High attenuation (low Qp) related to the geothermal system is found in the northeast of the Tarutung Basin suggesting fluid pathways from below the Sumatra Fault. The upper part of the studied geothermal system in the Tarutung district seems to be mainly controlled by the fault structure rather than by magmatic activities. In the southwest of the Tarutung Basin, the high attenuation zone is associated with the Martimbang volcano. In the Sarulla region, a low-Qp anomaly is found along the graben within the vicinity of the Hopong caldera.

Muksin, Umar; Haberland, Christian; Bauer, Klaus; Weber, Michael

2013-10-01

272

The Iceland Deep Drilling Project (IDDP): (6) Hydrothermal minerals record CO2 partial pressures in the Reykjanes Geothermal System, Iceland  

NASA Astrophysics Data System (ADS)

The Reykjanes Geothermal system, a target site for drilling by the IDDP, is located on the Reykjanes Peninsula in southwest Iceland, the landward extension of the Mid-Atlantic Ridge spreading center. Seawater penetrates the coastal Reykjanes geothermal system at depth, mixing with magmatic volatiles and reacting with the basaltic host rock to form secondary hydrothermal minerals. Within this system, epidote-prehnite-calcite- quartz-fluid constitutes a quadra-variant assemblage that, under conditions of specified temperature, pressure, and activity of H2O allows prediction of geothermal fluid pCO2 as a function of the composition of the solid solution minerals epidote or prehnite. This assemblage is typically found at temperatures >250°C and <~310°C, and potentially provides a mineralogical recorder that constrains fluid CO2 concentrations based on compositional zoning in hydrothermal epidote. Analysis of epidote crystals separated from drillhole-cuttings from three geothermal wells (RN-9, RN-10, RN-17) display complex chemical zoning, generally with Fe(III)-rich cores and Al-rich rims. The Fe(III)-mol fraction of epidote ranges 0.17 to 0.48. The Fe(III)-mol fraction of prehnite ranges from 0.11 to 0.59 in the upper portions of drillhole RN-17, where the highest Fe(III) content in epidote is 0.36, which serves as the upper Fe(III) limit for epidotes coexisting with prehnite in this study. Because most observed prehnite crystals in the drillhole-cuttings are too small for electron microprobe analyses (<20?m), we employed a sigmoidal correlation of available compositional data from active geothermal systems to calculate the Fe(III)-Al composition of prehnite using measured compositions of epidote in the Reykjanes system. In drill cuttings that contain epidote, prehnite, quartz and calcite, using measured epidote compositions between the reference temperatures of 275°C and 310°C, we calculated values of pCO2 for the geothermal fluids range from ~0.6 to ~6.2 bars. When only epidote, prehnite and quartz are observed in the drill cuttings, the calculated range of pCO2 is from ~1.3 to ~6.8 bars, which provides the maximum value of pCO2 at which calcite will not be present. Present day pCO2 values of geothermal fluids from the Reykjanes system were derived from analytical data on liquid and vapor samples collected at the surface using both the WATCH and SOLVEQ. At reference temperatures between 275°C and 310°C, these fluids have pCO2 concentrations ranging from 1.3 bars to 4.0 bars. The calculated pCO2 values based on epidote compositions are in close agreement with present-day fluid pCO2 in the Reykjanes geothermal system. 72% of the calculated pCO2 values based on epidote compositions where the assemblage of epidote, prehnite, quartz and calcite are observed in drill cuttings are within the range of measured present-day fluids, while 58% of the calculated pCO2 values fall within the range when calcite is not present in the drill cuttings.

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

2009-12-01

273

Enhanced Geothermal Systems in Urban Areas - Lessons Learned from the 2006 Basel ML3.4 Earthquake  

Microsoft Academic Search

We report on a recent deep-heat mining experiment carried out in 2006\\/2007 in the city of Basel (Switzerland). This pilot project was designed to produce renewable geothermal energy using the Enhanced Geothermal System (EGS) methodology. For developing the geothermal reservoir, a deep borehole was brought down to 5 km depth. Then, in December 2006, the deep-heat-mining project entered the first

T. Kraft; P. M. Mai; S. Wiemer; N. Deichmann; J. Ripperger; P. Kästli; C. E. Bachmann; D. Fäh; J. Woessner; D. Giardini

2009-01-01

274

Pressure-dependent Production Efficiency of an Enhanced Geothermal System (EGS): Stimulation Results and Implications for Hydraulic Fracture Treatments  

Microsoft Academic Search

A series of stimulation experiments were carried out at the geothermal research well in Groß Schönebeck (EGrSk 3\\/90) located\\u000a in the northeastem part of Germany. The intended purpose of these experiments was to develop concepts for a productivity increase\\u000a of the geothermal well to create an Enhanced Geothermal System (EGS). Two different kinds of stimulation types were performed.\\u000a Hydraulic gel-proppant

Günter Zimmermann; Torsten Tischner; Björn Legarth; Ernst Huenges

275

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

276

Mapping seismic attenuation within geothermal systems using teleseisms with application to the Geysers-Clear Lake region  

Microsoft Academic Search

Though the exact relationship between temperature and seismic attenuation has not been defined, the thermal regime of geothermal systems exhibit high seismic attenuation. The attenuation of a seismic wave is proportional to Q-1, the reciprocal of the quality factor. The reduced spectral ratio technique has been used to infer Q structure. This technique is adapated to study a geothermal system.

Ronald W. Ward; Chi-Yuh Young

1980-01-01

277

Statistical analysis of the induced Basel 2006 earthquake sequence: introducing a probability-based monitoring approach for Enhanced Geothermal Systems  

Microsoft Academic Search

Geothermal energy is becoming an important clean energy source, however, the stimulation of a reservoir for an Enhanced Geothermal System (EGS) is associated with seismic risk due to induced seismicity. Seismicity occurring due to the water injection at depth have to be well recorded and monitored. To mitigate the seismic risk of a damaging event, an appropriate alarm system needs

C. E. Bachmann; S. Wiemer; J. Woessner; S. Hainzl

2011-01-01

278

Landscape linkages between geothermal activity and solute composition and ecological response in surface waters draining the Atlantic slope of Costa Rica  

Microsoft Academic Search

Surface waters draining three different volcanoes in Costa Rica, ranging from dormant to moderately active to explosive, have a wide range of solute compositions that partly reflects the contribution of different types of solute-rich, geothermal waters. Three major physical transport vectors affect flows of geothermally derived solutes: thermally driven convection of volcanic gases and geothermal fluids; lateral and gravity-driven downward

CATHERINE M. PRINGLE; GARY L. ROWE; FRANK J. TRISKA; JOSE F. FERNANDEZ; JOHN WEST

1993-01-01

279

A 100% renewable electricity generation system for New Zealand utilising hydro, wind, geothermal and biomass resources  

Microsoft Academic Search

The New Zealand electricity generation system is dominated by hydro generation at approximately 60% of installed capacity between 2005 and 2007, augmented with approximately 32% fossil-fuelled generation, plus minor contributions from geothermal, wind and biomass resources. In order to explore the potential for a 100% renewable electricity generation system with substantially increased levels of wind penetration, fossil-fuelled electricity production was

I. G. Mason; S. C. Page; A. G. Williamson

2010-01-01

280

On production behavior of enhanced geothermal systems with CO 2 as working fluid  

Microsoft Academic Search

Numerical simulation is used to evaluate the mass flow and heat extraction rates from enhanced geothermal injection–production systems that are operated using either CO2 or water as heat transmission fluid. For a model system patterned after the European hot dry rock experiment at Soultz, we find significantly greater heat extraction rates for CO2 as compared to water. The strong dependence

Karsten Pruess

2008-01-01

281

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

282

Technical support for geopressured-geothermal well activities in Louisiana. Final report, 1 November 1983-31 October 1984  

SciTech Connect

This report describes environmental monitoring of microseismic activity, land-surface subsidence, and surface and ground-water quality at three designed geopressured-geothermal test well sites in Louisiana. Separate abstracts have been prepared for individual sections. (ACR)

Not Available

1985-12-01

283

Development of Models to Simulate Tracer Behavior in Enhanced Geothermal Systems  

SciTech Connect

A recent report found that power and heat produced from engineered (or enhanced) geothermal systems (EGSs) could have a major impact on the United States while incurring minimal environmental impacts. EGS resources differ from high-grade hydrothermal resources in that they lack sufficient temperature distributions, permeability/porosity, fluid saturation, or recharge of reservoir fluids. Therefore, quantitative characterization of temperature distributions and the surface area available for heat transfer in EGS is necessary for commercial development of geothermal energy. The goal of this project is to provide integrated tracer and tracer interpretation tools to facilitate this characterization. Modeling capabilities are being developed as part of this project to support laboratory and field testing to characterize engineered geothermal systems in single- and multi-well tests using tracers. The objective of this report is to describe the simulation plan and the status of model development for simulating tracer tests for characterizing EGS.

Williams, Mark D.; Vermeul, Vincent R.; Reimus, P. W.; Newell, D.; Watson, Tom B.

2010-06-01

284

CO2 DRIVEN HYDROTHERMAL ERUPTIONS IN GEOTHERMAL SYSTEMS OF TURKEY  

Microsoft Academic Search

Substantial CO2 degassing occurs from geothermal waters in Turkey as evident from ongoing deposition of recent terrace travertines and emplacement of significant travertine vein and breccia deposits representing hydrothermal eruption products. Geochemical data indicate rapid ascent of CO2- bearing fluids without significant interaction with basement and host rocks. High-precision U-series dates of most travertine veins coincide with times of cold\\/dry

I. Tonguç Uysal; Jian-xin Zhao; Yue-xing Feng; Suzanne D. Golding

2009-01-01

285

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

286

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

287

Near-Surface CO2 Monitoring And Analysis To Detect Hidden Geothermal Systems  

SciTech Connect

''Hidden'' geothermal systems are systems devoid of obvious surface hydrothermal manifestations. Emissions of moderate-to-low solubility gases may be one of the primary near-surface signals from these systems. We investigate the potential for CO2 detection and monitoring below and above ground in the near-surface environment as an approach to exploration targeting hidden geothermal systems. We focus on CO2 because it is the dominant noncondensible gas species in most geothermal systems and has moderate solubility in water. We carried out numerical simulations of a CO2 migration scenario to calculate the magnitude of expected fluxes and concentrations. Our results show that CO2 concentrations can reach high levels in the shallow subsurface even for relatively low geothermal source CO2 fluxes. However, once CO2 seeps out of the ground into the atmospheric surface layer, winds are effective at dispersing CO2 seepage. In natural ecological systems in the absence of geothermal gas emissions, near-surface CO2 fluxes and concentrations are predominantly controlled by CO2 uptake by photosynthesis, production by root respiration, microbial decomposition of soil/subsoil organic matter, groundwater degassing, and exchange with the atmosphere. Available technologies for monitoring CO2 in the near-surface environment include the infrared gas analyzer, the accumulation chamber method, the eddy covariance method, hyperspectral imaging, and light detection and ranging. To meet the challenge of detecting potentially small-magnitude geothermal CO2 emissions within the natural background variability of CO2, we propose an approach that integrates available detection and monitoring techniques with statistical analysis and modeling strategies. The proposed monitoring plan initially focuses on rapid, economical, reliable measurements of CO2 subsurface concentrations and surface fluxes and statistical analysis of the collected data. Based on this analysis, are as with a high probability of containing geothermal CO2 anomalies can be further sampled and analyzed using more expensive chemical and isotopic methods. Integrated analysis of all measurements will determine definitively if CO2 derived from a deep geothermal source is present, and if so, the spatial extent of the anomaly. The suitability of further geophysical measurements, installation of deep wells, and geochemical analyses of deep fluids can then be determined based on the results of the near surface CO2 monitoring program.

Lewicki, Jennifer L.; Oldenburg, Curtis M.

2005-01-19

288

Reservoir modelling of deep geothermal systems: the examples of Guardia Lombardi  

NASA Astrophysics Data System (ADS)

In the framework of the VIGOR project, a characterization of medium enthalpy geothermal resources was carried out in the Campania region (southern Italy), with a focus on the "Guardia dei Lombardi" area (Avellino). The VIGOR project started on the basis of an agreement between the Ministry of Economic Development and the Italian National Research Council, and it deals with the exploitation of innovative uses of geothermal energy in the so-called "regions of convergence" (Campania, Calabria, Puglia and Sicily). 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 possible geothermal exploitation of the carbonate reservoir. The preliminary results of our study suggest that "Guardia dei Lombardi" can be indicated as an interesting area for medium enthalpy geothermal exploitation, although the presence of a CO2 gas cap and the scaling capability of the deep fluids need to be carefully evaluated. The aim of this work is to give an estimation of a geothermal well productivity, in the case of a geothermal exploitation. The geothermal well that is thought to be more suitable in the Guardia dei Lombardi Area is named Bonito 1 Dir, a well with a measured temperature of 118 °C at 3,107m depth, which gives a corrected temperature of 138 °C with an error of 8 °C. The pressure was found to be nearly hydrostatic, with 266.9 bar at 2992.4 m depth, and the potential reservoir is hosted in the Mesozoic carbonate formation. According to hydraulic tests, we found that the permeability porosity product gives nearly 100 mD for the carbonatic formation. Since the matrix porosity is nearly 1% with 0.65 mD from core drilled tests, the result of the hydraulic test is to be related to a fractured system; in this case, there is no a clear relation among porosity and permeability, thus we had a sensitivity check on the possible porosity-permeability values of the system, keeping as a constrain the value obtained from the hydraulic test. From the 3D geological model we obtained the boundary of the carbonate formation hosting the geothermal reservoir, and we modelled the cases of both a single producing well and a geothermal doublet in order to give an estimation of the geothermal potential. Deposition of calcite in a formation may significantly reduce the inflow performance of geothermal wells producing brine with CO2-rich content. The key operational and reservoir parameters influencing the magnitude of impairment by calcite deposition were identified through the numerical modelling of the rate of calcite deposition and its effect on flow rate assuming idealized flow conditions. This is an important constrain for a well lifetime, especially in the case of a 138 °C well, because the power production requires a large fluid flow, and an encrustating fluid may severely affect the geothermal well performance. The results of the model, in terms of fluid flow at wellhead and scaling potential, will be available for an economic evaluation of the feasibility of geothermal exploitation of the Bonito 1 Dir well, in the Guardia dei Lombardi area.

Montegrossi, Giordano; Inversi, Barbara; Scrocca, Davide

2013-04-01

289

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

290

The role of convective geothermal systems in the generation, migration, and entrapment of oil  

SciTech Connect

Modern convective geothermal systems (for example, at Yellowstone National Park) and their fossil equivalents, epithermal mineral deposits (like McLaughlin, California) have traditionally been considered poor petroleum prospects. The concentrated heat which drives these systems is commonly viewed as a negative influence: in other words, any oil initially present in or generated by these systems is quickly degraded to a useless carbonaceous residue. This is true in extreme cases, but numerous examples from the Great Basin, the northern California Coast Ranges, and elsewhere suggest that under certain circumstances, geothermal systems can efficiently generate, transport, and entrap significant quantities of producible petroleum. B.R.T. Simoneit has shown that oil can be hydrothermally generated in an {open_quotes} instant{close_quotes} of geologic time. It follows, then, that away from geothermal systems` high-temperature centers (or in wholly moderate-temperature systems), the encompassing shallow thermal anomalies can distill large volumes of oil from otherwise immature hydrocarbon source rocks. Transport of this newly-generated oil is enhanced by the buoyant upwelling of heated aqueous fluid. Porosity for oil transport and storage is created or increased by hydrothermal dissolution of rock-forming or secondary silicates and carbonates. Finally, geothermal {open_quotes}self-sealing{close_quotes} -- the deposition of secondary minerals (especially silica and clay) at the margins of a system -- can provide a very effective hydrocarbon seal. Lee Allison has noted the coincidence of igneous intrusions and oil reservoirs in Nevada. It is suggested that here and elsewhere, both igneous-related and amagmatic geothermal systems in otherwise favorable settings should be viewed as prime petroleum exploration targets.

Hulen, J.B. [Univ. of Utah Research Institute, Salt Lake City, UT (United States)

1995-06-01

291

HIGH-TEMPERATURE GEOTHERMAL RESOURCES IN HYDROTHERMAL CONVECTION SYSTEMS IN THE UNITED STATES.  

USGS Publications Warehouse

The calculation of high-temperature geothermal resources ( greater than 150 degree C) in the United States has been done by estimating the temperature, area, and thickness of each identified system. These data, along with a general model for recoverability of geothermal energy and a calculation that takes account of the conversion of thermal energy to electricity, yielded an estimate of 23,000 MW//e for 30 years. The undiscovered component was estimated based on multipliers of the identified resource as either 72,000 or 127,000 MW//e for 30 years depending on the model chosen for the distribution of undiscovered energy as a function of temperature.

Nathenson, Manuel

1983-01-01

292

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

293

Lithosphere tectonics and thermo-mechanical properties: An integrated modelling approach for Enhanced Geothermal Systems exploration in Europe  

Microsoft Academic Search

Knowledge of temperature at drillable depth is a prerequisite in site selection for geothermal exploration and development of enhanced geothermal systems (EGS). Equally important, the thermo-mechanical signature of the lithosphere and crust provides critical constraints for the crustal stress field and basement temperatures where borehole observations are rare. The stress and temperature field in Europe is subject to strong spatial

S. Cloetingh; J. D. van Wees; P. A. Ziegler; L. Lenkey; F. Beekman; M. Tesauro; A. Förster; B. Norden; M. Kaban; N. Hardebol; D. Bonté; A. Genter; L. Guillou-Frottier; M. Ter Voorde; D. Sokoutis; E. Willingshofer; T. Cornu; G. Worum

2010-01-01

294

Numerical simulation to study the feasibility of using CO2 as a stimulation agent for enhanced geothermal systems  

Microsoft Academic Search

A major concern in the development of enhanced geothermal systems (EGS) is achieving and maintaining adequate injectivity, while avoiding the development of preferential short-circuiting flow paths such as those caused by thermally-induced stress cracking. Past researches have tended to focus primarily on thermal and hydraulic stimulation. Recent studies suggest that chemical stimulation may improve the performance of EGS reservoirs. Geothermal

T. Xu; W. Zhang; K. Pruess

2009-01-01

295

A materials and equipment review of selected US geothermal district heating systems  

SciTech Connect

This collection of information was assembled for the benefit of future geothermal system designers and existing system operators. It is intended to provide insight into the experience gained from the operation of 13 major geothermal systems over the past several years. Each chapter contains six or seven sections depending upon the type of system: introduction, production facilities, distribution, customer connections, metering and disposal. Some chapters, covering systems which incorporate a closed distribution design include a section on the central mechanical room. Each section details the original equipment and materials installed in that portion of the system. Following each section is a discussion of the subsequent problems, solutions and modifications relating to the equipment. The extent to which information was available varied from system to system. This is reflected in the length and level of detail of the chapters.

Rafferty, K.D.

1989-07-01

296

Evidence for thermal mining in low temperature geothermal areas in Iceland  

Microsoft Academic Search

This study deals with thermal mining in several geothermal systems in Iceland. A number of 2500- to 3000-m deep drillholes have been drilled into low temperature geothermal areas in the country. The conductive gradient outside active geothermal areas has also been mapped, and shows a systematic variation from lower than 50°C\\/km in the outer parts of the Tertiary basalts to

Jens Tómasson; Pórdur Arason

2000-01-01

297

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

National Technical Information Service (NTIS)

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 understa...

P. A. Candela P. M. Piccoli

2004-01-01

298

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

299

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

300

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

301

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

302

OPTIMIZATION OF THE ECONOMICS OF ELECTRIC POWER FROM ENHANCED GEOTHERMAL SYSTEMS  

Microsoft Academic Search

Based on a review of the Enhanced Geothermal Systems (EGS) developed to date, numerical simulation of idealized EGS reservoirs, economic sensitivity analysis, and practical considerations of certain site characteristics, this paper shows that certain steps can be taken towards optimizing the economics of an EGS project: These steps, in decreasing order of their importance, are as follows: (a) reduce the

Subir K. Sanyal

303

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

Microsoft Academic Search

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

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

2011-01-01

304

Development of Models to Simulate Tracer Behavior in Enhanced Geothermal Systems  

Microsoft Academic Search

A recent report found that power and heat produced from engineered (or enhanced) geothermal systems (EGSs) could have a major impact on the United States while incurring minimal environmental impacts. EGS resources differ from high-grade hydrothermal resources in that they lack sufficient temperature distributions, permeability\\/porosity, fluid saturation, or recharge of reservoir fluids. Therefore, quantitative characterization of temperature distributions and the

Mark D. Williams; Vincent R. Vermeul; P. W. Reimus; D. Newell; Tom B. Watson

2010-01-01

305

A Case Study of Wide Diameter Casing for Geothermal Systems  

SciTech Connect

Three wells have been drilled in the central resistivity area of a geothermal field in the Taupo Volcanic Zone, New Zealand. Using a well bore simulator, WELL SIM V3.0, reservoir conditions and well characteristics are evaluated to determine the increase in output by increasing production casing diameters from either 8-5/8 inches OD or 9-5/8 inches OD to 13-3/8 inches OD. Increases in well drilling costs are determined to provide a commentary on the economics. While open hole size is effectively doubled, well costs increase by 10% and, in this study, output increases by an average of 18%.

King, T.R.; Freeston, D.H.; Winmill, R.L.

1995-01-01

306

Integrated mineralogical and fluid inclusion study of the Coso geothermal systems, California  

SciTech Connect

Coso is one of several high-temperature geothermal systems on the margins of the Basin and Range province that is associated with recent volcanic activity. This system, which is developed entirely in fractured granitic and metamorphic rocks, consists of a well-defined thermal plume that originates in the southern part of the field and then flows upward and laterally to the north. Fluid inclusion homogenization temperatures and salinities demonstrate that cool, low salinity ground waters were present when the thermal plume was emplaced. Dilution of the thermal waters occurred above and below the plume producing strong gradients in their compositions. In response to heating and mixing, clays and carbonate minerals precipitated, sealing the fractures along the margins of the reservoir and strongly influencing its geometry. The alteration mineralogy varies systematically with depth and temperature. Based on the clay mineralogy, three zones can be recognized: the smectite zone, the illite-smectite zone, and the illite zone. The smectite zone thickens from the north to south and is characterized by smectite, kaolin, stilbite and a variety of carbonate minerals. The illite-smectite zone contains mixed-layer clays and also thickens to the south. The deepest zone (the illite zone) contains illite, chlorite, epidote, and wairakite. Quartz and calcite veins occur in all three zones. Comparison of mineral and fluid inclusion based temperatures demonstrates that cooling has occurred along the margins of the thermal system but that the interior of the system is still undergoing heating.

Lutz, Susan J.; Moore, Joseph N.; Copp, John F.

1996-01-24

307

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

308

Magnesium-silicate scaling in mixture of geothermal water and deaerated fresh water in a district heating system  

SciTech Connect

The low-temperature geothermal fields in Reykjavik utilized by the Reykjavik Municipal District Heating Service are now fully exploited. Additional hot water will be obtained by heating and deaerating fresh water using high temperature geothermal fluid. The heated fresh water will mix with low-temperature geothermal water in the distribution system in Reykjavik. A pilot plant has been set up to investigate magnesium silicate scale formation when mixing of these waters occurs. Tests show that the scale formation is dependent on the severity of deaeration of the fresh water the proportion of geothermal water in the mixture. Increased deaeration and thermal water proportion increase the pH of the mixture, and this promotes scaling. The scale formed is poorly crystalline, near amorphous trioctahedral smectite close to saponite in composition. By using minimum deaeration and traces of geothermal steam to remove the last remaining dissolved oxygen, scaling in the distribution system can be avoided.

Gunnlaugsson, E. (Hitaveita Reykjavikur, Grensasvegur 1, 108 Reykjavik (IE)); Einarsson, A. (Fosshals 3, 110 Reykjavik (IE))

1989-01-01

309

Enhanced Geothermal Systems in Urban Areas - Lessons Learned from the 2006 Basel ML3.4 Earthquake  

NASA Astrophysics Data System (ADS)

We report on a recent deep-heat mining experiment carried out in 2006/2007 in the city of Basel (Switzerland). This pilot project was designed to produce renewable geothermal energy using the Enhanced Geothermal System (EGS) methodology. For developing the geothermal reservoir, a deep borehole was brought down to 5 km depth. Then, in December 2006, the deep-heat-mining project entered the first critical phase when the water injections started for generating micro-fracturing of the rock. These fractures increase the permeability of the host rock, needed for efficient heat exchange between the rock and the cold water; however, these fracture are also source of micro-seismicity - small earthquakes that are continuously recorded and monitored by dedicated local seismic networks. In this stimulation phase, the seismic activity increased rapidly above the usual background seismicity, and culminated in a widely felt ML 3.4 earthquake, which caused some damage in the city of Basel. Due to the higher-than-expected seismic activity, and the reaction of the population, the media, and the politicians, the experiment was stalled only 6 days after the stimulations began. Although the injected water was allowed to escape immediately after the mainshock and pressure at the wellhead dropped rapidly, the seismic activity declined only slowly, with three ML > 3 events occurring one to two months later. Although the EGS technology has been applied and studied at various sites since the 1970s, the physical processes and parameters that control injection-induced seismicity - in terms of earthquake rate, size distribution and maximum magnitude - are still poorly understood. Consequently, the seismic hazard and risk associated with the creation and operation of EGS are difficult to estimate. The very well monitored Basel seismic sequence provides an excellent opportunity to advance the understanding of the physics of EGS. The Swiss Seismological Service (SED) is investigating the Basel dataset in the framework of the multidisciplinary research project GEOTHERM (www.geotherm.ethz.ch) Left) Seismic network in Basel, Switzerland. An epicenter map of the fluid injection-induced seismicity recorded by the seismic network, indicating high event densities in hot colors, is shown in the inset. Right) Fluid injection-induced seismicity recorded by the seismic network.

Kraft, T.; Mai, P. M.; Wiemer, S.; Deichmann, N.; Ripperger, J.; Kästli, P.; Bachmann, C. E.; Fäh, D.; Woessner, J.; Giardini, D.

2009-12-01

310

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

311

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

SciTech Connect

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/sup 0/C.

Ballantyne, J.M.

1980-06-01

312

Chinetsu koseinai netsukokan system donyu ni kansuru chosa. (Investigations on installation of the heat exchange system in geothermal wells).  

National Technical Information Service (NTIS)

The heat exchange system in geothermal wells is a system that replaces the air source heat pump and uses underground beds or groundwater as a heat source to heat rooms by collecting underground heat in winter, and cool rooms in summer by operating a heat ...

1996-01-01

313

Monitoring and mapping of hydrogen sulphide emissions across an active geothermal field: Rotorua, New Zealand  

NASA Astrophysics Data System (ADS)

Hydrogen sulphide (H2S) is one of a number of gaseous species associated with geothermal activity in the Taupo Volcanic Zone (TVZ), New Zealand. The city of Rotorua is located within Rotorua Caldera in the TVZ and is one of the few urban areas in the world where a large population (>60,000 people) is frequently exposed to geothermal emissions. In order to evaluate the health hazard from long-term exposure to H2S being emitted from the Rotorua geothermal field, a passive sampler has been developed to measure concentrations of H2S at many locations across the city simultaneously. In contrast to other passive or pump-based samplers, the sampler is inexpensive, easily mass-manufactured, and involves the reaction of H2S with silver halide contained in treated photographic paper. H2S-exposed paper shows a distinct colour change from white to dark brown as H2S concentrations increase and is sensitive to concentrations between ?30 and around 1000 ppb. Rotorua city can be divided into three regions—an area of low H2S concentration in the west, a ‘corridor’ of high concentrations running north south through the city centre where H2S is being emitted, and an area of medium concentration to the east which is influenced by the prevailing wind direction, creating a plume from the central corridor. The data give new insight into the subsurface routes of degassing in the Rotorua geothermal field, by showing the surface expression of the main upflow zone and the direction of the conjectured faulting below.

Horwell, C. J.; Patterson, J. E.; Gamble, J. A.; Allen, A. G.

2005-01-01

314

GEOGRAPHIC INFORMATION SYSTEMS IN MANAGING OF TERRITORIAL RESOURCES: AN EXAMPLE FOR THE SABATINI GEOTHERMAL SYSTEM (CENTRAL ITALY)  

NASA Astrophysics Data System (ADS)

Geographic Information System (GIS) is very important tool in managing the interdisciplinary researches and territorial resources. GIS integrates data for capturing, managing, analyzing, and displaying all forms of geographically referenced information. They can represent a scientific and social benefit. Here we present an application of GIS to a potentially exploitable geothermal area. The geothermal resource can be used either indirectly or directly. In the first case electricity is produced from high enthalpy systems. In second case heating and cooling systems are obtained from medium or low enthalpy systems. Italian geothermal resources employment is still poorly developed in direct use sector, despite the great geothermal potentials suitable for this purpuse. Often this limited application is due mainly to a inadequate territory knowledge and sometimes by difficulties in obtaining required information. In this case the creation of a geo-database can be extremely helpful. The studied area is located in Central Italy, just north of Rome, and comprise the western part of the Sabatini Volcanic District, Tolfa Mountains, extending up to Civitavecchia. Exploration surveys investigated this area during 70’s-90’s for geothermal purpose, but the area still results unexploited. The presence of thermal waters and of anomalous heat flow, together with demographical growing of the last years, make this site a suitable location for direct applications of the geothermal resource. Previews work and new data about geological, structural, hydrogeological, geochemical features have been processed to be recorded in a geo-database . Further, social data about demographical trend and available scientific record concerning the studied area fulfill the database. The majority of available geological information date back to early 90’s; an important part of the work consisted in the digitalization and updating of pre-existent data. The final product is a WEB-GIS that can facilitate diffusion and consultation of geographically referenced data, which can be easily managed by public and private infrastructures, research institutes and universities, allowing a better development of the territorial resources.

Procesi, M.; Cinti, D.; Poncia, P.; de Rita, D.

2009-12-01

315

Effect of Hydrothermal Alteration on Rock Properties in Active Geothermal Setting  

NASA Astrophysics Data System (ADS)

Hydrothermal alteration records the physical-chemical changes of rock and mineral phases caused by the interaction of hot fluids and wall rock, which can impact effective permeability, porosity, thermal parameters, rock strength and other rock properties. In this project, an experimental approach has been used to investigate the effects of hydrothermal alteration on rock properties. A rock property database of contrastingly altered rock types and intensities has been established. The database details horizontal and vertical permeability, porosity, density, thermal conductivity and thermal heat capacity for ~300 drill core samples from wells THM12, THM13, THM14, THM17, THM18, THM22 and TH18 in the Wairakei-Tauhara geothermal system (New Zealand), which has been compared with observed hydrothermal alteration type, rank and intensity obtained from XRD analysis and optical microscopy. Samples were selected from clay-altered tuff and intercalated siltstones of the Huka Falls Formation, which acts as a cap rock at Wairakei-Tauhara, and tuffaceous sandstones of the Waiora Formation, which is a primary reservoir-hosting unit for lateral and vertical fluid flows in the geothermal system. The Huka Falls Formation exhibits argillic-type alteration of varying intensity, while underlying Waiora Formations exhibits argillic- and propylithic-type alteration. We plan to use a tempered triaxial test cell at hydrothermal temperatures (up to 200°C) and pressures typical of geothermal conditions, to simulate hot (thermal) fluid percolation through the rock matrix of an inferred "reservoir". Compressibility data will be obtained under a range of operating (simulation reservoir) conditions, in a series of multiple week to month-long experiments that will monitor change in permeability and rock strength accompanying advancing hydrothermal alteration intensity caused by the hot brine interacting with the rock matrix. We suggest, our work will provide new baseline information concerning fluid-rock interaction processes in geothermal reservoirs, and their effects on rock properties, that will aid improved understanding of the evolution of high-temperature geothermal systems, provide constraints to parameterization of reservoir models and assist future well planning and design through prediction of rock properties in the context of drilling strategies.

Mikisek, P.; Bignall, G.; Sepulveda, F.; Sass, I.

2012-04-01

316

The Iceland Deep Drilling Project (IDDP): (6) Hydrothermal minerals record CO2 partial pressures in the Reykjanes Geothermal System, Iceland  

Microsoft Academic Search

The Reykjanes Geothermal system, a target site for drilling by the IDDP, is located on the Reykjanes Peninsula in southwest Iceland, the landward extension of the Mid-Atlantic Ridge spreading center. Seawater penetrates the coastal Reykjanes geothermal system at depth, mixing with magmatic volatiles and reacting with the basaltic host rock to form secondary hydrothermal minerals. Within this system, epidote-prehnite-calcite- quartz-fluid

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

2009-01-01

317

Physics-based Modeling of Rock Deformation and Fracturing Induced by Hydraulic Stimulation of Enhanced Geothermal System Reservoirs (Invited)  

Microsoft Academic Search

A key assumption associated with enhanced geothermal system reservoir creation\\/stimulation is that sufficient rock volumes can be hydraulically fractured via both tensile and shear failure, and more importantly by reactivation of naturally existing fractures (by shearing) to create the reservoir. The advancement of enhanced geothermal system greatly depends on our understanding of the dynamics of the intimately coupled rock-fracture-fluid system

H. Huang; R. K. Podgorney; S. Deng

2010-01-01

318

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

319

Elastomers for Geothermal Casing-Packer Seals: Four elastomeric systems for casing-packer seals performed satisfactorily at geothermal conditions.  

National Technical Information Service (NTIS)

This citation summarizes a one-page announcement of technology available for utilization. A report describes the development of elastomeric compounds for casing-packer seals that will withstand a 260C geothermal environment. A preliminary study had determ...

1982-01-01

320

Thermodynamic analysis of a geopressured geothermal hybrid wellhead power system. Final report  

SciTech Connect

This research project is designed to evaluate the performance and operating characteristics of hybrid power cycles applied to geopressured and geothermal resources. The power systems evaluated are from the EPRI geopressured wellheat project and data used for the analysis are from the Pleasant Bayou well site. Three types of hybrid power systems are analyzed thermodynamically. They are (A) the single flash system, (B) the double flash system, and (C) the binary system. The studies of the first two systems are more extensive than the third one, although the binary system is the one chosen for testing at the Pleasant Bayou well site.

Chang, I.; Williams, J.R.

1985-01-01

321

Geothermal district heating and cooling system for the city of Calistoga, California  

SciTech Connect

Calistoga has long been known for having moderate (270/sup 0/F maximum) hydrothermal deposits. The economic feasibility of a geothermal heating and cooling district for a portion of the downtown commercial area and city-owned building was studied. Descriptions of existing and proposed systems for each building in the block are presented. Heating and cooling loads for each building, retrofit costs, detailed cost estimates, system schematics, and energy consumption data for each building are included. (MHR)

Frederick, J.

1982-01-01

322

GTO-DOE/Industry Cost Shared Research; Microseismic Characterization and Monitoring in Geothermal Systems  

SciTech Connect

The application of passive seismic studies in geothermal regions have undergone significant changes in the last 15 years. The primary application is now in the monitoring of subsurface processes, rather than exploration. A joint Geothermal Technology Organization (GTO) industry/DOE, monitoring project involving GEO, Unocal Geothermal, and LBL, was carried out at The Geysers geothermal field in northern California using a special high frequency monitoring system. This several-month-long experiment monitored the discrete and continuous seismic signals before, during, and after a fluid stimulation of a marginal production well. Almost 350,000 liters of water were pumped into the well over a four-hour, and a three-hour time period for two consecutive days in June of 1988. No significant changes in the background seismicity or the seismic noise were detected during the monitoring period. Analysis of the background seismicity did indicate that the earthquakes at The Geysers contain frequencies higher than 50 Hz. and possibly as high as 100 Hz.

Majer, E.L.

1989-03-21

323

Geophysical logging case history of the Raft River geothermal system, Idaho  

SciTech Connect

Drilling to evaluate the geothermal resource in the Raft River Valley began in 1974 and resulted in the discovery of a geothermal reservoir at a depth of approximately 1523 m (500 ft). Several organizations and companies have been involved in the geophysical logging program. There is no comprehensive report on the geophysical logging, nor has there been a complete interpretation. The objectives of this study are to make an integrated interpretation of the available data and compile a case history. Emphasis has been on developing a simple interpretation scheme from a minimum of data sets. The Raft River geothermal system occurs in the Raft River Valley, which is a portion of the Basin and Range geomorphic province located in south central Idaho, south of the Snake River Plain. The valley is a late Cenozoic structural downwarp bounded by faults on the west, south, and east. The downwarp is filled with Tertiary and Paleozoic sediments, metasediments, and volcanics that overlie Precambrian rocks. The variety of rock types, the presence of alteration products, and the variability of fracturing make reliable interpretations difficult. However, the cross plotting of various parameters has allowed a determination of rock types and an analysis of the degree of alteration and the density of fractures. Thus, one can determine the relevant data necessary to assess a geothermal reservoir in similar rock types and use cross plots to potentially define the producing zones.

Applegate, J.K.; Moens, T.A.

1980-04-01

324

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

325

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

326

Preliminary Report on the Feasibility of Using Synthetic Aperture Radar Interferometry to Image Localized Strain as a Discriminator of Geothermal Resources.  

National Technical Information Service (NTIS)

Most producing geothermal fields and known geothermal resources in the Basin and Range province are associated with Quaternary active fault systems, within which hydrothermal fluids are presumed to circulate from depth to relatively shallow production lev...

W. Foxall

2005-01-01

327

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

328

Hybrid System for Snow Melting and Space Cooling by using Geothermal Energy  

NASA Astrophysics Data System (ADS)

This paper aims to develop a hybrid system for snow melting and space cooling by using geothermal energy in order to improve the availability factor of the borehole heat exchanger. Based on field experiments, a feasibility evaluation of the system was performed. First, snow melting experiments using geothermal energy were performed and the comparatively good road surface situation was realized. The primary energy reduction rate over 70% was shown in comparison with the conventional snow melting system. Second, regarding a snow melting tank with the hot water piping, it was clarified that the snow melting was possible even in the low temperature water of approximately 9-10°C by using water sprinkling in the tank jointly. Finally, by supplying the space cooling and dehumidification panel with the cold through the borehole heat exchanger in summer, it was shown that the good cooling effect was obtained.

Hamada, Yasuhiro; Nakamura, Makoto; Kubota, Hideki

329

Power-poor Philippines taps geothermal pool  

SciTech Connect

The current energy situation in the Philippines (75% imported oil) is reviewed and current and future activities in the area of geothermal energy use is discussed. It is estimated that by 1986, $830 million will be spent to develop the extensive geothermal sources to produce 13% of the nation's total energy. The high-quality geothermal sources are described as producing 162/sup 0/C water-steam mixture at a pressure of 6.68 kg/sec. Energy producing systems are described briefly as well as the environmental and equipment problems encountered already. The cost of geothermal energy is discussed (2.5 cents/kWh) and compared with energy costs of fossil-fuel and hydroelectricity. It is concluded that the geothermal energy sources should be a major contributor to the Philippines for at least 30 years. (MJJ)

Not Available

1982-04-15

330

Application of Microearthquake(MEQ)Monitoring for Characterizing the Performance of Enhanced Geothermal Systems  

NASA Astrophysics Data System (ADS)

Microearthquake monitoring for fracture enhancement and imaging of fracture systems will play a crucial role in the success of EGS, both from a reservoir management and public acceptance point of view. One controversial issue associated with EGS is the impact of induced seismicity or microseismicity, which has been the cause of delays and threatened cancellation of at EGS projects worldwide. LBNL is installing, operating , and/or interfacing MEQ seismic arrays at multiple EGS sites which are in collaboration with the USDOE Geothermal EGS Program. The overall goal is to gather high resolution MEQ data before, during and after stimulation activities at the EGS projects. This will include both surface and borehole deployments (as necessary and in conjunction with available boreholes) to not only use MEQ data for understanding the creation and monitoring of fracture stimulation of EGS reservoirs, but for using both active and passive monitoring of the fracture systems. Current EGS DOE Project sites include Desert Peak, Brady’s Hot Springs, and New York Canyon, Nevada, the NW Geysers, and the SE Geysers, California, Raft River, Idaho, and Newberry Caldera in Oregon. A possible additional site in Alaska. Additional sites will be instrumented as DOE adds projects. A second goal is to provide high quality MEQ data, improved processing methodologies to detect and understand fracture and fault mechanics,and advanced analysis of the data to the research community in order to develop, test and apply MEQ methods for understanding the performance of the EGS systems,as well as aid in developing induced seismicity mitigation techniques that can be used for a variety of EGS systems in the future. Reported will be current status and results from the initial injections and how the research community can access the data.

Majer, E.

2010-12-01

331

Geochronology and isotope transport systematics in a subsurface granite from the Larderello Travale geothermal system (Italy)  

NASA Astrophysics Data System (ADS)

A monzogranite, here referred to as the Montieri pluton, was encountered along two depth profiles from ca. 2 to 4 km depth in wells of the Larderello Travale geothermal system, Italy. We obtained high-resolution petrographic and microchemical data on seven fresh samples of the Montieri pluton. These data are required to correctly interpret the combined isotope data for the Rb Sr and K Ar systems. Biotite and K-feldspar from all samples were analyzed by Rb Sr and 39Ar 40Ar. Rb Sr analyses gave extremely variable two-point Rb Sr apparent ages and Sr initials, indicating that biotite did not equilibrate with feldspar. Bulk dissolution of K-feldspars does not define a Rb Sr alignment that could have proved a common origin of all K-feldspar samples from a single magma batch. The leachable fractions of K-feldspar separates have much more homogeneous 87Sr/86Sr ratios around 0.712, which may reflect the isotopic composition of a late-stage circulating fluid. Because of the anatectic origin of the granites from the Larderello Travale geothermal system, it is likely that every K-feldspar separate contains at least three isotopically distinct feldspar generations: relics of the Hercynian gneiss basement, Pliocene magmatic minerals, and hydrothermal retrogression products. Such heterogeneity can be confirmed and quantified by petrographical observations and electron microprobe analyses. The 39Ar 40Ar age spectra of the biotite samples show some internal discordance. Because of deviations from stoichiometry, biotite discordance can be attributed both to chlorite intergrowths, as predicted from the active fluid circulation, and to the presence of multiple biotite generations, such as have already been documented from other micas from the Larderello Travale geothermal system and as indeed confirmed by high-resolution petrography. Total K Ar biotite ages on cluster around 3 Ma and broadly agree with a Rb Sr age obtained by regressing only the biotite analyses. This suggests that the Montieri pluton, whose known volume is at least 25 km3, was emplaced at that time. The K-feldspar spectra are strongly discordant; no step age approaches the zero-age which would be predicted by Ar diffusivity modelling. The extraneous Ar in the feldspars is not excess Ar, but inherited Ar instead. Ar inheritance in the feldspar separates correlates with inheritance of Sr. Arrhenius trajectories of the apparent Ar diffusivities for all seven feldspars are astonishingly identical, despite the heterochemism amongst samples. However, the apparent diffusivity calculated from the step-heating experiments led to irreproducible models for the thermal history along the depth profile, as well as time-scales shorter than the historical record. This indicates that Ar diffusivities calculated from laboratory experiments must not be extrapolated to geological conditions.

Villa, Igor M.; Ruggieri, Giovanni; Puxeddu, Mariano; Bertini, Giovanni

2006-04-01

332

Double-diffusive convection in liquid-dominated geothermal systems with high-salinity brines  

SciTech Connect

Variations in temperature and salinity in hypersaline liquid-dominated geothermal systems like the Salton Sea Geothermal System (SSGS) tend to be correlated such that liquid density is relatively constant in the system. The tendency toward small density variations may be due to connectivity with a surrounding regional aquifer at multiple depths in the stratigraphic column. We present numerical simulation results for natural convection in geothermal systems like the SSGS in hydraulic connection with a constant-density aquifer. Natural convection where there are two sources of buoyancy such as heat and salt, with different diffusivities, is called double-diffusive convection. Simulations of double-diffusive convection are carried out using our general-purpose reservoir simulator TOUGH2 with a newly developed twodimensional heat and brine transport module (T2DM) that includes Fickian solute dispersion. The model includes an accurate formulation for liquid density as a function of temperature and salinity. Our simulation results show many features that are consistent with observations of the SSGS, making conceptual models that involve hydraulic connectivity with a surrounding aqulfer appear plausible. The generality of our model makes the results broadly applicable to systems similar to the SSGS.

Oldenburg, Curtis M.; Pruess, Karsten; Lippmann, Marcelo

1994-01-20

333

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

334

Enhanced Geothermal Systems Project Development Solicitation - Final Report - 09/30/2000 - 02/01/2001  

SciTech Connect

The Enhanced Geothermal System concept is to develop the technology required to extract energy from the reduced permeability zones that underlie all high-temperature geothermal systems. Our concept is that injection wells will be drilled into the high temperature zone. The wells will identify fractures that are only poorly connected to the overlying reservoir. Water injected into these fractures will cause them to propagate through thermal contraction, increase in hydrostatic pressure, and reduction of effective stress. The fractures will connect with the overlying normal temperature reservoir, and steam will be produced from existing production wells. The injection water will generate high thermal quality steam while mitigating problems relating to high gas and chloride.

Nielson, Dennis L.

2001-05-07

335

Hydrogeochemistry of the Qualibou Caldera Geothermal System, St. Lucia, West Indies  

SciTech Connect

Interpretation of hydrogeochemical data and supporting geologic and electric resistivity data have been used to define the basic structure of the Qualibou Caldera geothermal system and propose a model of hydrologic flow. The geothermal system at Sulphur Springs consists of three layers: (1) an upper steam condensate zone; (2) an intermediate vapor zone, which may be restricted to the Sulphur Springs area only; and (3) a lower brine zone. Four lines of evidence suggest that temperatures of the brine layer may exceed 230/sup 0/C at depths of perhaps 1 km. Outlying thermal springs along the northwest side of the caldera do not indicate derivation from underlying high-temperature sources. It is suggested that the main reservoir upflows in the Belfond-Sulphur Springs area and flows laterally in the subsurface toward the northwest caldera wall.

Goff, F.; Vuataz, F.D.

1984-01-01

336

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

337

Processes controlling water and hydrocarbon composition in seeps from the Salton Sea geothermal system, California, USA  

Microsoft Academic Search

Water-, mud-, gas-, and petroleum-bearing seeps are part of the Salton Sea geothermal system (SSGS) in Southern California. Seeps in the Davis-Schrimpf seep field (˜14,000 m2) show considerable variations in water temperature, pH, density, and solute content. Water-rich springs have low densities (<1.4 g\\/cm3), Cl contents as high as 45,000 ppm, and temperatures between 15 and 34 °C. Gryphons expel

Henrik Svensen; Dag A. Karlsen; Anne Sturz; Kristian Backer-Owe; David A. Banks; Sverre Planke

2007-01-01

338

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

339

On the production behavior of enhanced geothermal systems with CO2as working fluid  

Microsoft Academic Search

Numerical simulation is used to evaluate mass flow and heatextraction rates from enhanced geothermal injection-production systemsthat are operated using either CO2 or water as heat transmission fluid.For a model system patterned after the European hot dry rock experimentat Soultz, we find significantly greater heat extraction rates for CO2 ascompared to water. The strong dependence of CO2 mobility (=density\\/viscosity) upon temperature

Pruess

2007-01-01

340

Helium: a gaseous geochemical guide to faults, fractures and geothermal systems  

SciTech Connect

Helium-4, which is a product of radioactive decay in basement rocks, will preferentially migrate to the surface along deep-seated faults and fractures. The discovery of such fault and fracture systems is a key element in the exploration for geothermal deposits. Helium geochemistry provides a rapid, cost-effective and environmentally non-destructive exploration tool which can define concealed fracture zones. The applicability of this technique has been clearly demonstrated in regional and detailed prospect evaluations.

Kahler, D.E.

1981-10-01

341

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

342

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

343

Geothermal project description: LLL experimental site Salton Sea geothermal field  

Microsoft Academic Search

The Lawrence Livermore Laboratory program for geothermal research requires the development of a field experimental facility in order to conduct a series of tests on turbine prototypes and to analyze the system requirements for power conversion. This report gives a description of the field portion of this experimental program including site development, test activities, and project administration. Additionally, it discusses

T. D. Palmer; D. F. Towse

1975-01-01

344

Chusho chinetsu binary hatsuden system jisho shiken hokokusho. (Report on demonstration test on small- and medium-size geothermal binary power generation systems (1993)).  

National Technical Information Service (NTIS)

With relation to the geothermal binary power generation system, investigations were made on evaluation of economic efficiency, basic commercialization/introduction study, check and review of the power system, present scale prevention measures, etc. As for...

1995-01-01

345

Energy balance and economic feasibility of shallow geothermal systems for winery industry  

NASA Astrophysics Data System (ADS)

The search of energy efficient solutions has not yet been accomplished in agro-food constructions, for which technical studies and orientations are needed to find energy efficient solutions adapted to the environment. The main objective of this investigation is to evaluate the effectiveness of using shallow geothermal energy for the winery industry. World wine production in 2009 stood at 27100 millions of litres [1]. World spends 320 billion Euros on wine a year, according to industry insiders. On average, it is estimated that producing 1 litre of wine sold in a 75 cl glass bottle costs around 0.5-1.2 Euros /litre [2]. The process of ageing the wine could substantially increase production costs. Considering the time required for the aging of wine (months or years) and the size of the constructions, the use of an air conditioning system implies a considerable increase in energy consumption. Underground wine cellars have been in use for centuries for making and ageing wine. Ground thermal inertia provides protection from outdoor temperature oscillation and maintains thermal stability without energy consumption [3]. Since the last century, production of wine has moved to buildings above ground that have several advantages: lower construction cost, more space, etc. Nevertheless, these constructions require a large energy consumption to maintain suitable conditions for the ageing and conservation of wine. This change of construction techniques is the cause of an increase in energy consumption in modern wineries. The use of shallow geothermal energy can be a good alternative to take advantage of the benefits of aboveground buildings and underground constructions simultaneously. Shallow geothermal systems can meet the needs of heating and cooling using a single installation, maintaining low energy consumption. Therefore, it could be a good alternative to conventional HVAC systems. The main disadvantage of geothermal systems is the high cost of investment required. This paper analyzes the use of shallow geothermal systems in wineries, studying its feasibility versus conventional HVAC systems. A comparative analysis of six European locations will be performed. [1] OIV, Assessment on the world vitiviniculture situation in 2010, in, Organisation Internationale de la Vigne et du Vin, 2010. [2] FAO, Agribusiness Handbook: Grapes Wine, in, Investment Centre Division. FAO, 2009. [3] F.R. Mazarrón, J. Cid-Falceto, I. Cañas, An assessment of using ground thermal inertia as passive thermal technique in the wine industry around the world, Applied Thermal Engineering, 33-34 (0) (2012) 54-61.

Ruiz-Mazarrón, F.; Almoguera-Millán, J.; García-Llaneza, J.; Perdigones, A.

2012-04-01

346

Monitoring microearthquake activity and structure changes at the Coso geothermal area  

NASA Astrophysics Data System (ADS)

The Coso geothermal area, at the southern end of Owens Valley in eastern California, has been exploited for electricity generation for more than a decade, during which time a network of three-component digital borehole seismometers operated by the US Navy has monitored seismic activity. The several thousand locatable microearthquakes recorded each year by this network are well suited to using time-dependent crustal structure, hypocenter locations, and moment-tensor focal-mechanisms to monitor changes caused by production and by reservoir-stimulation experiments. Local-earthquake tomography results reported in 2003 show that between 1996 and 2002 the Vp/Vs ratio decreased in the uppermost 2 km, primarily because of an increase in Vs. This change might be caused by either drying of the rock matrix or a decrease in pore pressure. More detailed tomography, including all years from 1996 to 2003 and having improved horizontal resolution (1 km), now shows that this change occurred primarily in the most recent few years. Locating microearthquakes within the geothermal field by applying high-resolution relative relocation methods (e.g. Waldhauser and Ellsworth, 2000; Richards-Dinger and Shearer, 2000) to arrival-time differences determined by waveform cross-correlation reduces location errors by an order of magnitude (from 100s of meters to 10s of meters). Examples from reservoir-stimulation experiments in 2003 and 2004, when 14 portable seismometers supplemented the permanent seismic network, clearly delineate small structures upon which microearthquakes occur. High-resolution hypocenters are valuable supplements to complete moment-tensor earthquake mechanisms determined from body-wave amplitude ratios measured using the enlarged seismometer network, and help to constrain the physical processes occurring within the geothermal reservoirs better than either data type alone can do.

Julian, B. R.; Foulger, G. R.; Richards-Dinger, K.

2004-12-01

347

A three-dimensional thermo-poroelastic model for fracture response to injection\\/extraction in enhanced geothermal systems  

Microsoft Academic Search

Water injection in enhanced geothermal systems sets in motion coupled poro-thermo-chemo-mechanical processes that impact the reservoir dynamics and productivity. The variation of injectivity with time and the phenomenon of induced seismicity can be attributed to the interactions between these processes. In this paper, a three-dimensional transient numerical model is developed and used to simulate fluid injection into geothermal reservoirs. The

A. Ghassemi; X. Zhou

2011-01-01

348

Hydraulic stimulation of a deep sandstone reservoir to develop an Enhanced Geothermal System: Laboratory and field experiments  

Microsoft Academic Search

The geothermal research well GtGrSk4\\/05 at Groß Schönebeck, Germany, was hydraulically stimulated to develop an Enhanced Geothermal System in the Upper Rotliegend sandstones. Gel–proppant stimulation was selected to enhance reservoir productivity and to maintain it over the long term. Before the field tests, laboratory experiments were carried out to study embedding effects and long-term hydraulic conductivity changes in intermediate- and

Günter Zimmermann; Andreas Reinicke

2010-01-01

349

The Enhanced Geothermal System of Soultz-sous-Forêts: A study of the relationships between fracture zones and calcite content  

Microsoft Academic Search

The Enhanced Geothermal System (EGS) of Soultz-sous-Forêts (France) is made of three boreholes (GPK2, GPK3 and GPK4). The hydraulic connection between the wells, which is crucial to get an efficient geothermal exchanger, may be unfortunately hindered by the more or less complete sealing of fractures by hydrothermal neoformed minerals. This paper takes over the recent work of the authors that

Ronan L. Hébert; Béatrice Ledésert; Danièle Bartier; Chrystel Dezayes; Albert Genter; Céline Grall

2010-01-01

350

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.

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

2013-07-01

351

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

352

Hydrothermal fluids vented at shallow depths at the Aeolian islands: relationships with volcanic and geothermal systems.  

NASA Astrophysics Data System (ADS)

Scuba diving investigations carried out over the last two decades at the Aeolian islands revealed the existence of submarine magmatic and late-magmatic hydrothermalism at all the islands, despite the absence of on-shore activity at some of the islands. The results gained by diving activities provided useful information to evaluate the volcanic and geothermal activity and to manage the volcanic crisis occurred on November 2002 off the island of Panarea. Scuba diving investigations carried out from middle 80's, had shown that despite the absence of on shore volcanic manifestations, submarine hydrothermal activity is recognizable at shallow depth around all the Aeolian islands related either to volcanic and geothermal activity. The sampled gases are CO2-dominated with low amounts of oxygen and reactive gases (H2, CO, CH4 and H2S) with concentrations ranging from a few ppm to some mole percent. Sometimes significant N2 amount are detectable together with high helium contents. Samples having low CO2 content, besides relevant N2 and He amounts, are the consequence of CO2 dissolution in sea-water due to gas-water interactions (GWI) occurred before the sample collection. The high CO2 solubility (878 ml/l, T=20°C, P=1bar) may, in fact, decrease the CO2 content in the venting gases thus increasing the concentrations of the less soluble species (e.g. He 8 ml/l, CO 23 ml/l and CH4 33.8 ml/l) in the gas mixture. Such a process might occur at any level, however, because of the slow water circulation in deep sediments, CO2 is able to saturate the circulating sea-water. The isotopic composition of carbon displays a small range of values while helium isotopes are in the range of 4.1active and extinct Volcanoes, their chemical composition is similar. Contrastingly the isotope composition of helium shows a large heterogeneity with the highest isotopic ratios surprisingly measured at the extinct volcanic islands in the western sector, and much lower values detected in venting gases from active volcanoes (e.g. Vulcano and Panarea). The explanation of such a difference is not related to the volcanic activity at all, but to the parent mantle that in the western side looks to be less contaminated compared to the eastern side. Crustal contamination has been invoked by several authors as the main factor that caused the dramatic 3He/4He decrease. Although the parent mantle produced magmas with different isotopic signature, the gas phase looks similar. To explain the results of the chemical analyses it is proposed that similar deep boundary conditions (pressure, temperature, oxidation level) act as buffers for the chemical composition of the venting gases. With the aim of investigating their origin, estimations of the deep equilibration conditions have been carried out. The reactive compounds detected in the sampled gases, largely used for geothermometric and geobarometric considerations of hydrothermal fluids were used in a system based on the CH4-CO-CO2 contents assuming the presence of a boiling aqueous solution. The equilibrium constants of the adopted reactions are a function of temperature and oxygen fugacity, being the latter buffered by the mineral assemblage of the host rocks. Due to the similarity in the chemical composition of the gases vented at all the islands, a theoretical model developed to interpret the chemical composition of the gases released at Panarea during the last volcanic crisis is here applied. The results have shown that geothermal boiling systems are detectable at all the islands with temperatures up to 350°C. The adopted geo-thermobarometric system is more sensitive to the contents of CO and CH4 than that of CO2, implying that although GWI induce modifications in the chemical composition, the estimated equilibrium temperatures do not change very much for variations of the CO2 content in the range of several volume percent, thus, whether or not the gaseous mixture underwent GWI. Moreover, the slow reaction kinetics of CO and CH4 allow them to keep the deep equilibrium c

Italiano, Francesco; Caracausi, Antonio; Longo, Manfredi; Maugeri, Roberto; Paonita, Antonio

2010-05-01

353

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

354

Be in the Salton Sea Geothermal System, California (USA): Salton Sea Scientific Drilling Project, California State 2-14 well: Final report  

SciTech Connect

The Salton Sea Geothermal System lies in the old Colorado River Delta, where sediments have been metamorphosed by hydrothermal processes. Fluids, from well Fee No. 5 and deep hole SSSDP California State 2-14, as well as rocks from the deep hole were studied for /sup 10/Be and /sup 9/Be. In the solid samples /sup 10/Be concentration ranges from 29 to 259 /times/ 10/sup 6/ atom/g and /sup 9/Be from 0.49 to 2.52 ppM. The /sup 10/Be concentration in the geothermal waters ranges from 2 /times/ 10/sup 3/ to 2.9 /times/ 10/sup 6/ atom/g and /sup 9/Be from 0.7 to 16.6 ppB. Compared to the steady-state inventory which represents the quantity of /sup 10/Be expected from rain deposition alone (/approximately/1 /times/ 10/sup 12/ atom/cm/sup 2/), the /sup 10/Be inventory in the deep core is 3 orders of magnitude higher (>1 /times/ 10/sup 15/ atom/cm/sup 2/). This indicates that most /sup 10/Be is inherited and that the sediments hosting the geothermal field down to 3250m are young, less than few million year old. /sup 10/Be and /sup 9/Be Kds decrease from surface to bottom (3333 to 48 and 727 to 393, respectively) expressing the strong leaching effect of the solid material by the geothermal waters. This process is more active at depth where pH is <5.3 and salinity high (approx. =25%). Compared to other natural systems, Salton Sea Geothermal fluids are strongly enriched in /sup 10/Be and /sup 9/Be. Finally, contamination has been observed in the fluids samples and we developed a tool that is helping in detecting which samples are contaminated.

Valette-Silver, N.J.

1988-06-01

355

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

356

The Design of Large Geothermally Powered Air-Conditioning Systems Using an Optimal Control Approach  

NASA Astrophysics Data System (ADS)

The direct use of geothermal energy from Hot Sedimentary Aquifer (HSA) systems for large scale air-conditioning projects involves many tradeoffs. Aspects contributing towards making design decisions for such systems include: the inadequately known permeability and thermal distributions underground; the combinatorial complexity of selecting pumping and chiller systems to match the underground conditions to the air-conditioning requirements; the future price variations of the electricity market; any uncertainties in future Carbon pricing; and the applicable discount rate for evaluating the financial worth of the project. Expanding upon the previous work of Horowitz and Hornby (2007), we take an optimal control approach to the design of such systems. By building a model of the HSA system, the drilling process, the pumping process, and the chilling operations, along with a specified objective function, we can write a Hamiltonian for the system. Using the standard techniques of optimal control, we use gradients of the Hamiltonian to find the optimal design for any given set of permeabilities, thermal distributions, and the other engineering and financial parameters. By using this approach, optimal system designs could potentially evolve in response to the actual conditions encountered during drilling. Because the granularity of some current models is so coarse, we will be able to compare our optimal control approach to an exhaustive search of parameter space. We will present examples from the conditions appropriate for the Perth Basin of Western Australia, where the WA Geothermal Centre of Excellence is involved with two large air-conditioning projects using geothermal water from deep aquifers at 75 to 95 degrees C.

Horowitz, F. G.; O'Bryan, L.

2010-12-01

357

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.

358

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

359

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

360

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

361

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

362

Materials for geothermal production  

SciTech Connect

Advances in the development of new materials continue to be made in the geothermal materials project. Many successes have already been accrued and the results used commercially. In FY 1991, work was focused on reducing well drilling, fluid transport and energy conversion costs. Specific activities performed included lightweight CO{sub 2}-resistant well cements, thermally conductive and scale resistant protective liner systems, chemical systems for lost circulation control, corrosion mitigation in process components at The Geysers, and elastomer-metal bonding systems. Efforts to transfer the technologies developed in these efforts to other energy-related sectors of the economy continued and considerable success was achieved.

Kukacka, L.E.

1992-01-01

363

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

364

Geopressured Geothermal Bibliography (Geopressure Thesaurus).  

National Technical Information Service (NTIS)

This thesaurus of terminology associated with the geopressured geothermal energy field has been developed as a part of the Geopressured Geothermal Information System data base. A thesaurus is a compilation of terms displaying synonymous, hierarchical, and...

T. R. Hill K. Sepehrnoori

1981-01-01

365

Seismic Hazard Analysis as a Controlling Technique of Induced Seismicity in Geothermal Systems  

NASA Astrophysics Data System (ADS)

The effect of induced seismicity of geothermal systems during stimulation and fluid circulation can cover a wide range of values from light and unfelt to severe and damaging. If the design of a modern geothermal system requires the largest efficiency to be obtained from the social point of view it is required that the system could be managed in order to reduce possible impact in advance. In this framework, automatic control of the seismic response of the stimulated reservoir is nowadays mandatory, particularly in proximity of densely populated areas. Recently, techniques have been proposed for this purpose mainly based on the concept of the traffic light. This system provides a tool to decide the level of stimulation rate based on the real-time analysis of the induced seismicity and the ongoing ground motion values. However, in some cases the induced effect can be delayed with respect to the time when the reservoir is stimulated. Thus, a controlling system technique able to estimate the ground motion levels for different time scales can help to better control the geothermal system. Here we present an adaptation of the classical probabilistic seismic hazard analysis to the case where the seismicity rate as well as the propagation medium properties are not constant with time. We use a non-homogeneous seismicity model for modeling purposes, in which the seismicity rate and b-value of the recurrence relationship change with time. Additionally, as a further controlling procedure, we propose a moving time window analysis of the recorded peak ground-motion values aimed at monitoring the changes in the propagation medium. In fact, for the same set of magnitude values recorded at the same stations, we expect that on average peak ground motion values attenuate in same way. As a consequence, the residual differences can be reasonably ascribed to changes in medium properties. These changes can be modeled and directly introduced in the hazard integral. We applied the proposed technique to a training dataset of induced earthquakes recorded by Berkeley-Geysers network, which is installed in The Geysers geothermal area in Northern California. The reliability of the techniques is then tested by using a different dataset performing seismic hazard analysis in a time-evolving approach, which provides with ground-motion values having fixed probabilities of exceedence. Those values can be finally compared with the observations by using appropriate statistical tests.

Convertito, V.; Sharma, N.; Maercklin, N.; Emolo, A.; Zollo, A.

2011-12-01

366

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

367

Effect of geothermal waste on strength and microstructure of alkali-activated slag cement mortars  

SciTech Connect

Mortars of blast furnace slag replaced with 10% of a geothermal silica waste were cured for 90 days. The binder was activated by 6 wt.% Na{sub 2}O equivalent of NaOH and water glass. The presence of the silica enhanced the formation of hydration products as shown by nonevaporable water (NEW) results. Backscattered electron images indicated that the microstructures of blended slag had less porosity than those of neat slag mortars and the interfacial zone between aggregate and hydration products was dense and of homogeneous composition similar to the matrix of hydration products. The main hydration products were C-S-H and for NaOH a hydrotalcite type phase was found as finely intermixed with the C-S-H.

Escalante-Garcia, J.I.; Gorokhovsky, A.V.; Mendoza, G.; Fuentes, A.F

2003-10-01

368

Geothermal materials development  

SciTech Connect

Advances in the development of new materials, the commercial availabilities of which are essential for the attainment of Hydrothermal Category Level 1 and 2 Objectives, continue to be made in the Geothermal Materials Development Project. Many successes have already been accrued and the results transferred to industry. In FY 1990, the R D efforts were focused on reducing well drilling and completion costs and on mitigating corrosion in well casing. Activities on lost circulation control materials, CO{sub 2}- resistant lightweight cements, and thermally conductive corrosion and scale-resistant protective liner systems have reached the final development stages, and cost-shared field tests are planned for the FY 1991--1992 time frame. Technology transfer efforts on high temperature elastomers for use in drilling tools are continuing under Geothermal Drilling Organization (GDO) sponsorship.

Kukacka, L.E.

1991-02-01

369

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

370

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

371

Natural analogs for enhanced heat recovery from geothermal systems  

Microsoft Academic Search

High-temperature hydrothermal systems are physically;\\u000aand chemically zoned with depth. The energy input;\\u000ais from a magmatic zone, intruded by igneous bodies,;\\u000athat may also contribute variable amounts of magmatic;\\u000afluid to the system. The heat source is directly;\\u000aoverlain by a section of rocks, that due to their elevated;\\u000atemperature, respond to stress in a ductile fashion.;\\u000aThe ductile

Nielson; Dennis L

1996-01-01

372

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

National Technical Information Service (NTIS)

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 geother...

K. Zacny M. Hedlund P. T. Taylor S. Nagihara

2012-01-01

373

Geothermal Cooling Retrofit System. Third Quarter Report; Fourth Quarter Report.  

National Technical Information Service (NTIS)

Use of ground source air cooling is described. It was found that summer humidity in Oklahoma was too high for good performance of the system. Modifications to the house and addition of an air source heat pump to the ground tubes were discussed. (ERA citat...

B. R. Farrar

1982-01-01

374

Cost Analysis of Environmental Control Systems applicable to Geothermal Energy Development  

SciTech Connect

This report provides an engineering performance and cost correlations from which user could estimate costs of mitigating principal emissions from geothermal power systems. Hydrogen sulfide abatement describes four processes; Iron catalyst, Stretford, EIC, and Dow oxygenation process. Wastewater treatments include: Chemical precipitation, Evaporation ponds, Injection without pretreatment, and Injection with pretreatment. Process and cost estimates are given for Best Case, Most Probable Case, and Worst Case 50 MWe power plant. The cases may be confusing since the worst case has the lowest resource temperature, but the highest loads to mitigate. (DJE 2005)

None

1982-08-01

375

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

376

Imperial County geothermal development  

NASA Astrophysics Data System (ADS)

The progress of geothermal development during the past 3 years, county activities in support of geothermal development, and current challenges and future needs of the geothermal industry and the county are summarized. Three additional Known Geothermal Resources Areas (KGRAs) were identified: the Westmorland KGRA, the East Brawley KGRA, and the South Brawley KGRA. Three 10 megawatt power plants began operations during the grant period. Three commercial power plants are scheduled to begin construction during late 1982 or early 1983. Site work was begun for the Heber Flash Power Plant. Two commercial power plants are in planning stages.

1982-10-01

377

Enhanced geothermal systems (EGS) using CO 2 as working fluid—A novel approach for generating renewable energy with simultaneous sequestration of carbon  

Microsoft Academic Search

Responding to the need to reduce atmospheric emissions of carbon dioxide, Brown [Brown, D., 2000. A Hot Dry Rock geothermal energy concept utilizing supercritical CO2 instead of water. In: Proceedings of the Twenty-Fifth Workshop on Geothermal Reservoir Engineering, Stanford University, pp. 233–238] proposed a novel enhanced geothermal systems (EGS) concept that would use carbon dioxide (CO2) instead of water as

Karsten Pruess

2006-01-01

378

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

Microsoft Academic Search

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

Ahmad Ghassemi

2009-01-01

379

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

Microsoft Academic Search

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

Roy A. Cunniff; Roger L. Bowers

2003-01-01

380

Vapliq hydrothermal systems, and the vertical permeability of Los Azufres, Mexico, geothermal reservoir  

SciTech Connect

We identify a new category of natural hydrothermal systems intermediate between liquid- and vapor-dominated. This category is characterized by a “vapliq” vertical pressure profile, which is nearly vaporstatic in the shallower portion of the system, and nearly boiling-point-for-depth at depth. The prototype of these systems is the geothermal field of Los Azufres, Mexico. To explore the thermohydrological conditions conducent to this type of system, we propose a 1-D vertical scenario based on generally accepted conceptual models of liquid- and vapor-dominated geothermal reservoirs. We use the corresponding mass and thermal energy transport equations to establish that a necessary condition for the existence of 2-phase hydrothermal systems is that the absolute value of the vertical thermal flux must exceed Q{sub min}, a parameter that depends only on the values of the pressure and of the thermal conductivity at the boiling point of the system. The values of Q{sub min} are typically 1-4 times the average terrestrial flux. We also find that geothermal systems in which convective heat transport is accomplished by the well-known heat-pipe mechanism can exist only if the corresponding heat flux exceeds Q{sub min} and the permeability at the boiling point of the system is smaller than k{sub Bmax}, a parameter that depends only on the values of the pressure and of the thermal conductivity at the boiling point. Typical values of k{sub Bmax} are 1-3 {times} 10{sup -18} m{sup 2}, suggesting a reason for the fact that all vapor-dominated systems are associated with very-low matrix permeability formations. Applying these insights, and the mass and heat transport equations to Los Azufres, we conclude that a contrast of 1-3 orders of magnitude exists between the vertical permeability at the boiling point and that corresponding to the vapor-dominated portion of the system. We propose that similar permeability contrasts may be responsible for the characteristic composite pressure observed in other vapliq systems.

Iglesias, Eduardo R.; Arellano, Victor M.

1988-01-01

381

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

382

Geothermal resource exploration  

SciTech Connect

Exploration for geothermal resources in the Basin and Range geomorphic province of the western United States is much akin to mineral resource exploration. In this region, potential geothermal resources are located at or near zones of intersection of normal faults, where fracture permeability permits deep circulation of meteoric water into high-temperature areas afforded by high regional heat flow. Exploration encompasses regional surveys, covering several thousand square kilometres, followed by more detailed studies of several hundred square kilometres to identify sites for deep drillholes. The most effective methods for regional exploration are geologic studies based on areal multispectral surveys, heat-flow drilling, chemical geothermometry of warm- and cold-water sources, and age-dating of rock. Detailed heat-flow-hydrologic surveys, gravity and active-seismic surveys, and geologic mapping are most effective in locating targets for deep confirmatory drilling. Geochemical-halo surveys may also be very effective in both regional and areal exploration. Results of geochemical, radiochemical, and geophysical surveys combine to furnish a comparison of long-term flow rates of geothermal systems, thereby permitting preliminary evaluation of the relative viability of the systems.

Wollenberg, H.A.

1982-01-01

383

Modelling Studies of the Evolution of Vapour-Dominated Geothermal Systems  

SciTech Connect

Numerical experiments, based on linear stability results, are invoked to model the evolution of two-phase vapor-dominated zones within geothermal systems. A reservoir model with all boundaries impermeable to fluid flow and a uniform heat flux at the bottom boundary is used. The results obtained show that different steady-states are accessible along different quasi-static paths from the same initial vapor-dominated steady-state. Thus, the realization of a steady-state with a two-phase vapor-dominated zone overlying a single-phase hot water region can indicate that the geothermal system undergoes a process of slow cooling. A steady-state with a two-phase vapor-dominated zone overlying a single-phase vapor region can be formed either as a result of slow heating or as a result of a reduction in permeability. A steady-state with an upper vapor-dominated part and a lower liquid-dominated part can occur if permeability of the system has been gradually increased.

Pestov, I.

1995-01-01

384

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

385

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

386

Geothermal energy  

Microsoft Academic Search

The potential of a geothermal area is primarily dependent on volume and temperature of the reservoir and adequacy of fluid supply. Inadequate fluid supply may be a more common limiting factor than inadequate heat supply, for heat stored in the upper 10,000 ft of many hot spring systems is 1,000 to 10,000 times their annual natural heat flow. Except in

D. E. White

1966-01-01

387

Imperial County geothermal development. Quarterly report, January 1-March 31, 1982  

SciTech Connect

The activities of the Geothermal Office are reported including: important geothermal events, geothermal waste disposal, grant applications to the California Energy Commission, the planned geothermal development meeting, and other geothermal planning activities. The activities of the Geothermal Planner include processing of applications for geothermal permits, processing of environmental impact reports, and other geothermal planning activities. The progress on the VTN Corporation direct heat study is discussed.

Not Available

1982-03-31

388

Modular tube bundle heat exchanger and geothermal heat pump system  

SciTech Connect

An improved ground source heat pump system is described, comprising: an in-ground heat exchanger and a building heat exchanger coupled via conduits for refrigerant to at least one compressor and at least one expander, the compressor having at least one intake line and at least one discharge line, the compressor and the expander being coupled to the conduits such that the refrigerant is circulated in the conduits through pressure changes and corresponding temperature changes in the refrigerant, the in-ground heat exchanger comprising at least one modular tube bundle comprising a plurality of substantially horizontally oriented subterranean tubes, buried in a substantially planar vertical array for installation along substantially vertical walls of at least one that is backfilled for setting the array in thermal engagement with the earth, said at least one bundle having a top and bottom displaced vertically from one another, and the refrigerant being subjected to phase change in the conduits.

Galiyano, M.J.; Wiggs, B.R.; Aspacher, J.T.

1993-07-06

389

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

390

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

391

Geothermal direct-heat utilization assistance: Federal assistance program. Quarterly project progress report, October--December 1995  

SciTech Connect

The report summarizes geothermal technical assistance, R&D and technology transfer activities of the Geo-Heat Center at Oregon Institute of Technology for the first quarter of FY-96. It describes 90 contacts with parties during this period related to technical assistance with geothermal direct heat projects. Areas dealt with include geothermal heat pumps, space heating, greenhouses, aquaculture, equipment and resources. Research activities are summarized on low-temperature resource assessment, geothermal district heating system cost evaluation and silica waste utilization project. Outreach activities include the publication of a geothermal direct use Bulletin, dissemination of information, geothermal library, technical papers and seminars, development of a webpage, and progress monitor reports on geothermal resources and utilization.

NONE

1996-02-01

392

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.; Nuti, S.; D`Amore, F. [Ist. Internazionale per le Ricerche Geotermiche, Pisa (Italy); Gonfiantini, R. [International Atomic Energy Agency, Vienna (American Samoa). Isotope Hydrology

1993-10-01

393

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

394

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

395

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

396

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

397

Thermal Energy Recovery from Enhanced Geothermal Systems - Evaluating the Potential from Deep, High-Temperature Resources  

NASA Astrophysics Data System (ADS)

Enhanced Geothermal Systems (EGS) are geothermal reservoirs that require some form of stimulation to develop the permeability necessary for the circulation of hot water and the recovery of heat for electric power generation. A variety of mechanical, chemical and thermal approaches to reservoir stimulation have been proposed and tested over more than three decades of research on EGS technology, with the primary focus at present on enhancing fracture permeability by elevating fluid pressure sufficiently to induce shear failure along pre-existing natural fractures. A critical issue in assessing the potential EGS resource is quantifying Rg, the geothermal recovery factor, which is defined as the ratio of produced thermal energy to the thermal energy contained in the fractured volume comprising the reservoir. Some published EGS resource assessments incorporate the assumption that a constant amount of thermal energy is recovered during the life of a project, regardless of the temperature of the reservoir, thereby concluding that there is a decrease in Rg with increasing temperature and a reduced potential associated with deep, higher temperature resources. By contrast, production experience and simulations of thermal energy recovery from naturally fractured geothermal reservoirs indicate that Rg , which typically falls in the range from 0.05 to 0.2, is primarily a function of internal reservoir structure, not temperature. Because the thermal energy content of the crust increases linearly with increasing temperature, if the characteristics of Rg for naturally fractured reservoirs apply to EGS reservoirs, proportionally greater resource potential is associated with the deeper, hotter portions of the Earth’s crust, despite the costs and challenges associated with creating and exploiting reservoirs at greater depths and higher temperatures. Both numerical models of EGS thermal energy recovery and studies of analogous naturally fractured reservoirs indicate that Rg will remain relatively constant with increasing depth and temperature, making deep, hot reservoirs more attractive development targets. However, other aspects of production from deep, hot EGS reservoirs need further evaluation, such as the relative effects on productivity of declining fluid viscosity with increasing temperature, fracture closure at higher levels of effective stress, and the increased rates of mineral precipitation and dissolution at higher temperatures.

Williams, C.

2009-12-01

398

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

399

Chemical reaction path modeling of hydrothermal mineralization in the Tongonan geothermal field, Leyte (Philippines)  

Microsoft Academic Search

The study of hydrothermal processes in an active geothermal system provides an excellent opportunity to test the equilibrium between the hydrothermal mineral assemblage and present-day fluid. Simulations of selected hydrothermal processes in the Tongonan geothermal system were performed to ascertain the effectiveness of different depositional mechanisms for hydrothermal minerals. Hydrothermal processes, such as boiling, fluid mixing and water–rock interaction were

Maria Ines Rosana Balangue-Tarriela

2004-01-01

400

Geothermal direct-heat utilization assistance. Quarterly report, January - March 1997  

SciTech Connect

This report summarizes geothermal technical assistance, R&D and technology transfer activities of the Geo-Heat Center at Oregon Institute of Technology for the second quarter of FY-97. It describes 176 contacts with parties during this period related to technical assistance with geothermal direct heat projects. Areas dealt with include geothermal heat pumps, space heating, greenhouses, aquaculture, equipment, economics and resources. Research activities are summarized on well pumping in commercial groundwater heat pump systems. A memorandum of understanding between the GHC and EIA is described. Work accomplishments on the Guidebook are discussed. Outreach activities include the publication of a geothermal direct use Bulletin, dissemination of information, geothermal library, technical papers and seminars, and progress monitor reports on geothermal resources and utilization.

Lienau, P.

1997-04-01

401

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

402

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

403

Geochemistry of solid materials from two US geothermal systems and its application to exploration. Final: volume 77-14  

SciTech Connect

Initial development of geochemical techniques for exploration and exploitation of geothermal systems is described. The techniques are based on analysis of solid materials. Distribution of Cu, Mo, Pb, Zn, Ag, As, Sb, Co, Ni, Mn, Fe, Bi, B, Te, In, Sn, and W are determined and evaluated for several sample types in a hot water system (Roosevelt Hot Springs, Utah) and a vapor dominated system (Geysers, California). The sample types analyzed are magnetic fractions, whole rock samples, and two different heavy liquid separates derived from cuttings composites from geothermal wells and shallow rotary drill holes. The results show that multi-element geochemical zoning is developed at both a relatively small scale of over hundreds of feet around individual steam entries (SEs) and hot water entries (HWEs) in geothermal wells, and at a larger scale of over thousands of feet both vertically and laterally in geothermal systems. Zoning is surprisingly similar for both hot-water and vapor-dominated systems. Trace elements which display the most consistent and useful zoning characteristics are As, Sb, Pb, Zn, Mn, B, and W. Optimum delineation of the zoning is provided by +3.3 heavy liquid (HL) samples compared to the other sample types evaluated. Utilization of +3.3 samples maximizes detection of hydrothermal trace elements and markedly reduces or eliminates chemical signatures specifically related to rock type.

Bamford, R.W.

1978-07-01

404

Session 1: Geothermal Pumping Systems and Two-Phase Flow Studies  

SciTech Connect

Improvements in electric submersible pumping systems have resulted in a demonstrated downhole running life of one year for low horsepower units operating in 180 C brine. The implementation of a prototype pressurized lubrication system to prevent brine intrusion and loss of lubricating oil from the motor and protector sections has been successfully tested. Second generation pressurized lubrication systems have been designed and fabricated and will be utilized in downhole production pumping tests during FY84. Pumping system lifetime is currently limited by available power cable designs that are degraded by high-temperature brine. A prototype metal-sheathed power cable has been designed and fabricated and is currently undergoing destructive and nondestructive laboratory testing. This cable design has the potential for eliminating brine intrusion into the power delivery system through the use of a hermatically sealed cable from the surface to the downhole motor. The two-phase flow program is directed at understanding the hydrodynamics of two-phase flows. The two-phase flow regime is characterized by a series of flow patterns that are designated as bubble, slug, churn, and annular flow. Churn flow has received very little scientific attention. This lack of attention cannot be justified because calculations predict that the churn flow pattern will exist over a substantial portion of the two-phase flow zone in producing geothermal wells. The University of Houston is experimentally investigating the dynamics of churn flow and is measuring the holdup over the full range of flow space for which churn flow exists. These experiments are being conducted in an air/water vertical two-phase flow loop. Brown University has constructed and is operating a unique two-phase flow research facility specifically designed to address flow problems of relevance to the geothermal industry. An important feature of the facility is that it is dedicated to two-phase flow of a single substance (including evaporation and condensation) as opposed to the case of a two-component two-phase flow. This facility can be operated with horizontal or vertical test sections of constant diameter or with step changes in diameter to simulate a geothermal well profile.

Hanold, R.J.

1983-12-01

405

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

406

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

407

THE CASE OF A GEOTHERMAL HEAT PUMP SYSTEM WITH A COMPACT GROUND HEAT EXCHANGER IN DRY SOIL AND SOLAR PANELS RECHARGING  

Microsoft Academic Search

In the near future, in the ground source heat pumps industry compact ground heat exchangers will probably be an answer in case of small gardens, without expensive drilling of boreholes. Solar recharging of ground loops is today a field of research in the geothermal heat pumps industry. This article illustrates the case history of a 10kW geothermal heat pump system

D. Maritan

2008-01-01

408

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

409

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

410

Potential for surface gas flux measurements in exploration and surface evaluation of geothermal resources  

Microsoft Academic Search

Anomalous concentrations of CO2 and, to a lesser extent, CH4 have been detected over many active geothermal systems. The production of these gases, and of N2O, can be affected by both geothermal and biological processes. In this investigation, soil gas and soil-gas fluxes were measured at the Cove Fort-Sulphurdale geothermal field in Utah, which produces steam from both liquid- and

Ronald W Klusman; Joseph N Moore; Michael P LeRoy

2000-01-01

411

Working fluids of a low-temperature geothermally-powered Rankine cycle for combined power and heat generation system  

Microsoft Academic Search

A novel combined power and heat generation system was investigated in this study. This system consists of a low-temperature\\u000a geothermally-powered organic Rankine cycle (ORC) subsystem, an intermediate heat exchanger and a commercial R134a-based heat\\u000a pump subsystem. The advantages of the novel combined power and heat generation system are free of using additional cooling\\u000a water circling system for the power generation

Tao Guo; HuaiXin Wang; ShengJun Zhang

2010-01-01

412

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

413

Evolution of the thermal cap in two wells from the Salton Sea geothermal system, California  

SciTech Connect

The Salton Sea geothermal system is overlain by a thermal cap of low permeability rocks that restricts the upward movement of the high-temperature reservoir brines. Petrographic and fluid inclusion data from two wells show that the thermal cap in the southern part of the field consists of an upper layer of lacustrine and evaporite deposits with low initial permeabilities and a lower layer of deltaic sandstones. The sandstones were incorporated into the thermal cap as downward percolating fluids deposited anhydrite and calcite in the pore space of the rocks, reducing their permeabilities. During development of the thermal cap, base-metal sulfides, potassium feldspar and quartz veins were deposited by brines from higher temperature portions of the system.

Moore, Joseph N.; Adams, Michael C.

1988-01-01

414

Development of Active Seismic Vector-Wavefield Imaging Technology for Geothermal Applications  

SciTech Connect

This report describes the development and testing of vector-wavefield seismic sources that can generate shear (S) waves that may be valuable in geothermal exploration and reservoir characterization. Also described is a 3-D seismic data-processing effort to create images of Rye Patch geothermal reservoir from 3-D sign-bit data recorded over the geothermal prospect. Two seismic sources were developed and tested in this study that can be used to illuminate geothermal reservoirs with S-waves. The first was an explosive package that generates a strong, azimuth-oriented, horizontal force vector when deployed in a conventional shot hole. This vector-explosive source has never been available to industry before. The second source was a dipole formed by operating two vertical vibrators in either a force or phase imbalance. Field data are shown that document the strong S-wave modes generated by these sources.

B. A. Hardage; J. L. Simmons, Jr.; M. DeAngelo

1999-10-01

415

Numerical studies of fluid-rock interactions in EnhancedGeothermal Systems (EGS) with CO2 as working fluid  

Microsoft Academic Search

There is growing interest in the novel concept of operating Enhanced Geothermal Systems (EGS) with CO instead of water as heat transmission fluid. Initial studies have suggested that CO will achieve larger rates of heat extraction, and can offer geologic storage of carbon as an ancillary benefit. Fluid-rock interactions in EGS operated with CO are expected to be vastly different

Tianfu Xu; Karsten Pruess; John Apps

2008-01-01

416

A comparative study on exergetic assessment of two ground-source (geothermal) heat pump systems for residential applications  

Microsoft Academic Search

Ground source heat pumps (GSHPs), also known as geothermal heat pumps (GHPs), have been widely used for years in developed countries due to their higher energy utilization efficiencies than those of both conventional heating and cooling systems. However, they have been applied to the Turkish residential buildings since 1997.This study deals with the exergetic performance evaluation of two types of

Ebru Kavak Akpinar; Arif Hepbasli

2007-01-01

417

Numerical Studies of Fluid-Rock Interactions in Enhanced Geothermal Systems (EGS) with CO(sub2) as Working Fluid.  

National Technical Information Service (NTIS)

There is growing interest in the novel concept of operating Enhanced Geothermal Systems (EGS) with CO2 instead of water as heat transmission fluid. Initial studies have suggested that CO2 will achieve larger rates of heat extraction, and can offer geologi...

J. Apps K. Pruess T. Xu

2008-01-01

418

MASSIVELY PARALLEL FULLY COUPLED IMPLICIT MODELING OF COUPLED THERMAL-HYDROLOGICAL-MECHANICAL PROCESSES FOR ENHANCED GEOTHERMAL SYSTEM RESERVOIRS  

Microsoft Academic Search

Development of enhanced geothermal systems (EGS) will require creation of a reservoir of sufficient volume to enable commercial-scale heat transfer from the reservoir rocks to the working fluid. A key assumption associated with reservoir creation\\/stimulation is that sufficient rock volumes can be hydraulically fractured via both tensile and shear failure, and more importantly by reactivation of naturally existing fractures (by

Robert Podgorney; Hai Huang; Derek Gaston

2010-01-01

419

Enhanced Geothermal Systems Research and Development: Models of Subsurface Chemical Processes Affecting Fluid Flow  

SciTech Connect

Successful exploitation of the vast amount of heat stored beneath the earth’s surface in hydrothermal and fluid-limited, low permeability geothermal resources would greatly expand the Nation’s domestic energy inventory and thereby promote a more secure energy supply, a stronger economy and a cleaner environment. However, a major factor limiting the expanded development of current hydrothermal resources as well as the production of enhanced geothermal systems (EGS) is insufficient knowledge about the chemical processes controlling subsurface fluid flow. With funding from past grants from the DOE geothermal program and other agencies, we successfully developed advanced equation of state (EOS) and simulation technologies that accurately describe the chemistry of geothermal reservoirs and energy production processes via their free energies for wide XTP ranges. Using the specific interaction equations of Pitzer, we showed that our TEQUIL chemical models can correctly simulate behavior (e.g., mineral scaling and saturation ratios, gas break out, brine mixing effects, down hole temperatures and fluid chemical composition, spent brine incompatibilities) within the compositional range (Na-K-Ca-Cl-SO4-CO3-H2O-SiO2-CO2(g)) and temperature range (T < 350°C) associated with many current geothermal energy production sites that produce brines with temperatures below the critical point of water. The goal of research carried out under DOE grant DE-FG36-04GO14300 (10/1/2004-12/31/2007) was to expand the compositional range of our Pitzer-based TEQUIL fluid/rock interaction models to include the important aluminum and silica interactions (T < 350°C). Aluminum is the third most abundant element in the earth’s crust; and, as a constituent of aluminosilicate minerals, it is found in two thirds of the minerals in the earth’s crust. The ability to accurately characterize effects of temperature, fluid mixing and interactions between major rock-forming minerals and hydrothermal and/or injected fluids is critical to predict important chemical behaviors affecting fluid flow, such as mineral precipitation/dissolution reactions. We successfully achieved the project goal and objectives by demonstrating the ability of our modeling technology to correctly predict the complex pH dependent solution chemistry of the Al3+ cation and its hydrolysis species: Al(OH)2+, Al(OH)2+, Al(OH)30, and Al(OH)4- as well as the solubility of common aluminum hydroxide and aluminosilicate minerals in aqueous brines containing components (Na, K, Cl) commonly dominating hydrothermal fluids. In the sodium chloride system, where experimental data for model parameterization are most plentiful, the model extends to 300°C. Determining the stability fields of aluminum species that control the solubility of aluminum-containing minerals as a function of temperature and composition has been a major objective of research in hydrothermal chemistry.

Moller, Nancy; Weare J. H.

2008-05-29

420

Imperial County geothermal development quarterly report, July 1-September 30, 1983  

SciTech Connect

The highlights of geothermal development in Imperial County during July, August, and September 1983 are discussed. Topics include the status of geothermal development projects in the county, geothermal staff activities and research projects, and other geothermal-related topics.

Not Available

1983-10-01