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Injection recovery based on production data in unit 13 and unit 16 areas of The Geysers field

Description: Steam production data from 13 wells including and surrounding Unit 13 injection well I-3 and 15 production wells including and surrounding Unit 16 injection well I-5 are analyzed to estimate steam decline rates with and without water injection. Such information is then utilized to estimate the first year recovery factor due to water injection in the southwest area of Unit 13 and the Unit 16 wellfields.
Date: January 1, 1992
Creator: Goyal, K.P. & Box, W.T., Jr.
Partner: UNT Libraries Government Documents Department

Boiling and condensation processes in the Cerro Prieto beta reservoir under exploitation

Description: The deep Cerro Prieto (Baja California, Mexico) beta reservoir is offset vertically by the southwest-northeast trending, normal H fault. Under exploitation pressures in the upthrown block have decreased strongly resulting in boiling and high-enthalpy production fluids. Significant differences in fluid chemical and isotopic compositions are observed in the two parts of the reservoir and particularly in an anomalous zone associated with the H fault. These differences result from intense boiling and adiabatic steam condensation, as well as from leakage of overlying cooler water along the fault.
Date: January 1, 1992
Creator: Truesdell, Alfred; Manon, Alfredo; Quijano, Luis; Coplen, Tyler & Lippmann, Marcelo
Partner: UNT Libraries Government Documents Department

An accurate formulation of the solubility of Co{sub 2} in water, for geothermal applications

Description: The solubility correlations for the H{sub 2}O-CO{sub 2} system applied so far for numerical simulation of geothermal reservoir and well flows are crude. This is due, at least partly, to the significant disagreement existing between the solubility models and results published in the specialized literature. In this work we analyze the reasons underlying this disagreement. On this basis, we propose a thermodynamically correct, and numerically accurate model for the solubility of carbon dioxide in water. Its range of validity is up to 350 C and 500 bar. Our main contributions are: (a) the adoption of an equation of state for the gas phase that realistically accounts for the non-ideal behavior of both components and that of the mixture, within the P-T range considered; and (b) to accurately include the effects of temperature and pressure on the solubility of carbon dioxide in the liquid phase. The proposed model fits the available phase equilibrium data for the H{sub 2}O-CO{sub 2} system nicely. In particular, it does not present the severe conflict between the linearity of the model and the lack of linearity of the data, evident in earlier models. The tight fit obtained with our model indicates that the complexities of H{sub 2}-CO{sub 2} phase equilibrium are well represented by it.
Date: January 1, 1992
Creator: Iglesias, Eduardo R. & Moya, Sara L.
Partner: UNT Libraries Government Documents Department

Chemical water/rock interaction under reservoir condition

Description: A simple model is proposed for water/rock interaction in rock fractures through which geothermal water flows. Water/rock interaction experiments were carried out at high temperature and pressure (200-350 C, 18 MPa) in order to obtain basic solubility and reaction rate data. Based on the experimental data, changes of idealized fracture apertures with time are calculated numerically. The results of the calculations show that the precipitation from water can lead to plugging of the fractures under certain conditions. Finally, the results are compared with the experimental data.
Date: January 26, 1995
Creator: Watanabe, K.; Tanifuji, K.; Takahashi, H.; Wang, Y.; Yamasaki, N. & Nakatsuka, K.
Partner: UNT Libraries Government Documents Department

Potential for a Low-Temperature Geothermal Resource Near Mackay, Idaho

Description: Four water samples were collected from springs in the Mackay, Idaho area to investigate the potential for a direct-heat geothermal resource. The maximum measured temperature was 22 C for a spring south of Mackay. Calculation of the mineral equilibrium relationships in the calcium-bicarbonate water samples indicates that these samples equilibrated with the carbonate reservoir rocks. The temperatures of equilibration suggest that the subsurface temperatures of these water samples are probably no higher than measured surface temperatures.
Date: October 1, 1984
Creator: Sibbett, Bruce S. & Capuano, Regina M.
Partner: UNT Libraries Government Documents Department

An experimental study of the phase change by in-situ vaporization in porous medium

Description: A natural geothermal reservoir is an aquifer generally in liquid phase confined between two impermeable layers of rock. Drilling of such reservoirs causes a decompression which allows the in-situ vaporization of some water and the development of a dual-phase flow. Dual-phase flow is directed by the fractures of the reservoir; energy extinction is mainly determined by heat and mass transfers between the rock and the fluids. A large part of the energy stored in the reservoir is the heat of the rock, so the knowledge of these two interconnected mechanisms is very important to appreciate the behavior of geothermal reservoirs.
Date: January 1, 1978
Creator: Castanier, L. & Bories, S.
Partner: UNT Libraries Government Documents Department

A pore network model for adsorption in porous media

Description: Using a pore network model to represent porous media we investigate adsorption-desorption processes over the entire range of the relative pressure, highlighting in particular capillary condensation. The model incorporates recent advances from density functional theory for adsorption-desorption in narrow pores (of order as low as 1 nm), which improve upon the traditional multi-layer adsorption and Kelvin's equation for phase change and provide for the dependence of the critical pore size on temperature. The limited accessibility of the pore network gives rise to hysteresis in the adsorption-desorption cycle. This is due to the blocking of larger pores, where adsorbed liquid is allowed to but cannot desorb, by smaller pores containing liquid that may not desorb. By allowing for the existence of supercritical liquid in pores in the nm range, it is found that the hysteresis area increases with an increase in temperature, in agreement with experiments of water adsorption-desorption in rock samples from The Geysers. It is also found that the hysteresis increases if the porous medium is represented as a fractured (dual porosity) system. The paper finds applications to general adsorption-desorption problems but it is illustrated here for geothermal applications in The Geysers.
Date: January 26, 1995
Creator: Satik, Cengiz & Yortsos, Yanis C.
Partner: UNT Libraries Government Documents Department

A review of the UK Geothermal Hot Dry Rock R&D Programme

Description: The UK Department of Energy's Geothermal Hot Dry Rock (HDR) Program was last reviewed in 1987/88, when a number of technical problems were identified. These related to the size of reservoir (heat exchanger), its thermal behavior (short circuits) and water losses. A program of work to address these problems was subsequently set up. This work has recently been reviewed. The main conclusions are: (1) a satisfactory procedure for creating a commercial-scale HDR reservoir has yet to be demonstrated; (2) there is a dearth of information on rock properties at the 6-7 km depths needed for a commercial reservoir; (3) a satisfactory method of sealing short circuits has not yet been demonstrated; (4) although it is difficult to determine accurately the economics of HDR because of these technical uncertainties, it is believed that electricity from a commercial HDR power station is unlikely to be competitive with conventional means of generation in the short to medium term; (5) despite the earlier promise of the technology, HDR has been shown over the past two years to be still at an early stage of development and it is unlikely to attract private sector funding in the short term; and (6) participation in a joint European program offers the opportunity of resolving some of the technical uncertainties.
Date: January 1, 1991
Creator: Symons, Geoff D. & Clarke, John H.
Partner: UNT Libraries Government Documents Department

Some approaches to rock mass hydrofracture theory

Description: A new engineering method has been developed at the Leningrad Mining Institute for defining hot dry rock hydrofracturing parameters. It reflects the structural features of a real jointed rock mass, its gravity-tectonic components of the stress tensor and volume character of deformations, taking into account the inertial effects of hydrodynamics in the non-Darcy zone of radial fluid flow near the injection well, and conversion of the heat energy extracted from hot rock by circulating water partly into filtration-flow additional pressure. Results of calculations are compared to field experiments at Fenton Hill, NM, and are used for the first HDR circulation systems in the USSR.
Date: January 1, 1991
Creator: Dyadkin, Yuri, D.
Partner: UNT Libraries Government Documents Department

Session 4: Geothermal Reservoir Definition

Description: The study of geothermal reservoir behavior is presently in a state of change brought about by the discovery that reservoir heterogeneity--fractures in particular--is responsible for large scale effects during production. On the other hand, some parts of a reservoir, or some portions of its behavior. may be unaffected by fractures and behave, instead, as if the reservoir were a homogeneous porous medium. Drilling has for many years been guided by geologists prospecting for fractures (which have been recognized as the source of production), but until recently reservoir engineers have not studied the behavior of fractured systems under production. In the last three years research efforts, funded by the Department of Energy and others, have made significant progress in the study of fractures. The investigations into simulation of fracture flow, tracer analysis of fractured systems, and well test analysis of double porosity reservoirs are all advancing. However, presently we are at something of a conceptual impasse in defining a reservoir as fractured or porous. It seems likely that future directions will not continue to attempt to distinguish two separate reservoir types, but will focus instead on defining behavior types. That is, certain aspects of reservoir behavior may be considered to be generally of the porous medium type (for example, field wide decline), while others may be more frequently fracture type (for example, breakthrough of reinjected water). In short, our overall view of geothermal reservoir definition is becoming a little more complex, thereby better accommodating the complexities of the reservoirs themselves. Recent research results already enable us to understand some previously contradictory results, and recognition of the difficulties is encouraging for future progress in the correct direction.
Date: December 1, 1983
Creator: Horne, Roland N.
Partner: UNT Libraries Government Documents Department

Session 8: Hot Dry Rock Update

Description: In 1970, Los Alamos began an informal study of the possible usefulness of hot dry rock (HDR) energy systems based on circulation of water through hydraulic fractures connecting two wellbores drilled into hot crustal rock of low initial permeability and free-water content. In 1973 this was established as a formal HDR Program. It has since been sponsored by DOE and its predecessor agencies, with supplementary support since 1980 by agencies of the governments of West Germany and Japan. In the meantime, complementary HDR projects have been initiated in Germany, Japan, the United Kingdom, Sweden, France, and the Soviet Union, and several other countries have undertaken HDR resource evaluations and theoretical background studies. The HDR Program is now truly international, although the broadest and most advanced effort is still at Los Alamos.
Date: December 1, 1983
Creator: Whetten, John; Brown, David & Potter, Robert
Partner: UNT Libraries Government Documents Department

Research Drill Hole at the Summit of Kilauea Volcano, Hawaii

Description: An exploration hole has been drilled to a depth of 1262 m beneath the summit of Kilauea Volcano on the Island of Hawaii in order to obtain information about the potential for the occurrence of geothermal energy in a basalt environment. The hole was started at an elevation of 1102 m, and bottomed at an elevation of -160 m. Short intervals were cored, but the principal information obtained from the hole was in the form of physical measurements. The temperature profile through the hole was complicated, showing several reversals, and reached a maximum value of 137 C at the bottom. Geophysical logs indicate that rocks are fully water saturated to an elevation of about 500 m above sea level, and that the water in the rock has a salinity about equal to or slightly greater than that of sea water. This result supports the pre-drilling hypothesis that there should be a convection cell formed of warm saline water above a shallow magma chamber at Kilauea Volcano.
Date: January 1, 1974
Creator: Keller, G. V.
Partner: UNT Libraries Government Documents Department

Response of East Mesa and Raft River Reservoirs to Injection-Backflow Testing

Description: Analysis of tracer recovery curves from injection-backflow testing at two geothermal reservoirs reveals large differences in response between the two. The East Mesa reservoir is in a layered sandstone matrix, and tracer behavior can be adequately described by porous media theory. As the volume of water injected into the reservoir increases and, consequently, the depth of penetration into the formation, the ratio of dispersive flux to advective flux decreases, indicating the increasing importance of advective transport. This effect can be seen in normalized tracer recovery curves that become more symmetrical with greater injection volume. At the Raft River site, the reservoir is dominated by a single major fracture zone. Injecting larger volumes of water into the fracture does not change the shape of the normalized tracer recovery curves. This indicates that the dispersion coefficient increases proportionally to the distance traveled by the injection front. Differences in the shape of tracer recovery curves are related to fundamental differences in reservoir characteristics. Long tails on the tracer recovery curves at Raft River suggest a dual porosity reservoir with a secondary fracture network connected to the major fracture. Such findings may considerably affect calculations of secondary heat recovery using injection wells.
Date: December 15, 1983
Creator: Russell, B.F.; Hull, L.C. & Downs, W.F.
Partner: UNT Libraries Government Documents Department

Doublet Tracer Testing in Klamath Falls, Oregon

Description: A tracer test was carried out in a geothermal doublet system to study the injection behavior of a developed reservoir known to be fractured. The doublet produces about 320 gpm of 160 F water that is used for space heating and then injected; the wells are spaced 250 ft apart. Tracer breakthrough was observed in 2 hours and 45 minutes in the production well, indicating fracture flow. However, the tracer concentrations were low and indicated porous media flow; the tracers mixed with a reservoir volume much larger than a fracture.
Date: December 15, 1983
Creator: Gudmundsson, J.S.; Johnson, S.E.; Horne, R.N.; Jackson, P.B. & Culver, G.G.
Partner: UNT Libraries Government Documents Department

Vapour generation in hot permeable rock through injection of water

Description: We present a non-linear model to describe vapor generation in a hot, permeable rock through injection of water. We develop similarity solutions describing the steady injection of fluid from a line source. A systematic parameter study has shown that, with other parameters fixed, as (1) the reservoir pressure increases, the mass fraction vaporized decreases; (2) the reservoir temperature increases, the mass fraction vaporized increases; (3) as the mass injection rate increases, the mass fraction vaporized decreases; and (4) as the porosity increases, the mass fraction vaporized decreases. We then present similarity solutions which describe injection from (1) a point source, with the mass flux injected proportional to t{sup 1/2}; and (2) a planar source, with the mass flux injected proportional to t{sup -1/2}, where t is the time of injection. These results suggest that for steady injection, the vapor production gradually increases for injection from a point source, and gradually decreases for planar injection. We confirm this prediction with numerical calculations describing the vapor production resulting from steady injection from line, point and planar sources.
Date: January 1, 1992
Creator: Fitzgerald, Shaun D. & Woods, Andrew W.
Partner: UNT Libraries Government Documents Department

The Kinetics of Quartz Dissolution and Precipitation

Description: Silica precipitation in geothermal power plants and in reservoir formations is considered to be a potential problem area in the successful development of geothermal power from liquid dominated resources. In order to gain insight into the significance of this problem and to estimate the rates of precipitation of silica under varying conditions, a literature review and evaluation was made. Data on the kinetics of quartz dissolution and precipitation in water was fitted to an expression derived from absolute rate theory, assuming that the mechanism could be represented by the equation: SiO{sub 2} + 2H{sub 2}O = Si(OH){sub 4}.
Date: January 1, 1976
Creator: Apps, J.A.
Partner: UNT Libraries Government Documents Department

HDR reservoir analysis incorporating acoustic emission data

Description: A set of models of HDR systems is presented which attempts to explain the formation and operation of HDR systems using only the in-situ properties of the fractured rock mass, the earth stress field, the engineering intervention applied by way of stimulation and the relative positions and pressures of the well(s). A statistical and rock mechanics description of fractures in low permeability rocks provides the basis for modeling of stimulation, circulation and water loss in HDR systems. The model uses a large number of parameters, chiefly simple directly measurable quantities, describing the rock mass and fracture system. The effect of stimulation (raised fluid pressure allowing slip) on fracture apertures is calculated, and the volume of rock affected per volume of fluid pumped estimated. The total rock volume affected by stimulation is equated with the rock volume containing the associated AE (microseismicity). The aperture and compliance properties of the stimulated fractures are used to estimate impedance and flow within the reservoir. Fluid loss from the boundary of the stimulated volume is treated using radial leak-off with pressure-dependent permeability.
Date: January 26, 1995
Creator: Willis-Richards, J.; Watanable, K.; Yamaguchi, T. & Takasugi, A.
Partner: UNT Libraries Government Documents Department

Geothermal Modeling of the Raft River Geothermal Field

Description: This interim report presents the results to date of chemical modeling of the Raft River KGRA. Earlier work indicated a northwest-southeast anomaly in the contours. Modeling techniques applied to more complete data allowed further definition of the anomaly. Models described in this report show the source of various minerals in the geothermal water. There appears to be a regional heat source that gives rise to uniform conductive heat flow in the region, but convective flow is concentrated near the upwelling in the Crook well vicinity. Recommendations are made concerning field expansion and additional work needed to refine the overall reservoir model.
Date: November 1, 1979
Creator: Overton, H.L.; Chaney, R.E.; McAtee, D.L. & Graham, D.L.
Partner: UNT Libraries Government Documents Department

Thermodynamic transient behavior of a geothermal fracture

Description: This paper presents a space integrated zero dimensional model that describes the thermodynamic behavior of a geothermal fracture undergoing exploitation. The main assumptions involved are: fluid and energy entering the fracture come from the surrounding matrix, fracture of infinite conductivity, and that the steam and water phases are gravitationally segregated and in thermodynamic equilibrium. The nonlinear equations of mass and energy conservation are numerically solved. A sensitivity analysis on the main parameters that affect this problem was carried out. Water recharge is described by a linear infinite aquifer, and heat flow from the matrix to the fluid was also considered by means of a linear infinite system. The behavior of the system is clearly described for conditions of exploitation in the steam, in the water, or mixed completion in both steam and water zones.
Date: January 26, 1995
Creator: Ascencio, F.; Samaniego, F.; Cinco-Ley, H. & Rivera, J.
Partner: UNT Libraries Government Documents Department

Pressures in the Wairakei Geothermal Field (NZ) in its Natural State

Description: The near-surface pressure distribution in the Wairakei Geothermal Field prior to exploitation is estimated from early bore hole measurements and drilling logs. Pressure distributions in a bore were rarely measured but can be calculated from the recorded temperature profiles. For a number of bores, a depth and corresponding pressure was estimated, to associate with the undisturbed field conditions, by examining drilling logs for major circulation losses in uncased sections and temperature patterns for internal flows between feeding fissures. In the shallower boiling zone of the field, some points of rapid temperature rise were found in cased sections of bores. These were interpreted as being heated by flow of boiling fluid in fissures outside the casing, and pressures were obtained for these depths from the highest temperatures recorded at them, assuming the fluid to be pressurized water at its boiling point.
Date: January 1, 1995
Creator: McNabb, A. & Dickinson, G.
Partner: UNT Libraries Government Documents Department

An experimental measurement of the adsorption of super-heated steam

Description: The adsorption of liquid water in a vapor-dominated geothermal reservoir is one way the rocks hold fluids. The presence of this adsorbed water must be taken into account in the evaluation of the reservoir capacity. A great number of papers have been published in the last ten years on this matter (see for instance [Hornbrook, 1994], and [Economides, 1985]); at Stanford University a big effort was carried out in experimental measurements of the adsorption/desorption from reservoir samples (see [Shang, 1994]). In Italy we have a new geothermal field not exploited yet, in the Monteverdi region (southern border of Larderello), where 16 productive wells were found, supplying two 20 MW geothermal units. All the wells produce superheated steam. The effect of adsorbed water was simulated, and the results will be presented in WGC 95 [Bertani, 1995].
Date: January 26, 1995
Creator: Bertani, Ruggero; Perini, Renato & Tarquini, Bruno
Partner: UNT Libraries Government Documents Department

Update on the Long-Term Flow Testing Program

Description: Preliminary flow and pressure testing of the Phase II Hot Dry Rock (HDR) reservoir at Fenton Hill, New Mexico, as part of the preparations for the initial 90-day segment of the Long-Term Flow Test, has revealed several significant features concerning the hydraulic behavior of this reservoir as a function of injection and production pressure levels. Of most significance to the future operation of HDR power plants is the influence of elevated production backpressure on the effective reservoir flow impedance (i.e., the difference between injection and production pressures, divided by the production flow rate). It has been found that the effective flow impedance at high backpressure is significantly lower than the corresponding impedance at low backpressure. At an injection pressure of 3700 psi and a back-pressure of 2210 psi, the effective flow impedance for the present reservoir is 20 psi/gpm--less than 40% of the effective flow impedance for similar injection conditions, but at low backpressure (about 170 psi). Recently, a 10-day reservoir flow test was conducted at a somewhat lower backpressure of 1500 psi, and at a slightly higher injection pressure of 3750 psi. At these new conditions, there was an increase in the effective reservoir flow impedance to 23.6 psi/gpm, but also a significant increase in the production flow rate and temperature--from 74 gpm to 95 gpm, and from 154 C to 180 C. The net reservoir water loss rate averaged over the last 5 days of this latest flow test was 7.3 gpm, which corresponds to a net recovery of 93% of the injected water--a very significant result that has been obtained from our preliminary reservoir flow testing. Under both of these high backpressure flow conditions, the reservoir was not extending, as evidenced by a very low rate of water loss and the absence of microseismic activity.
Date: March 24, 1992
Creator: Brown, Donald W.
Partner: UNT Libraries Government Documents Department

Pollution Control Guidance for Geothermal Energy Development

Description: This report summarizes the EPA regulatory approach toward geothermal energy development. The state of knowledge is described with respect to the constituents of geothermal effluents and emissions, including water, air, solid wastes, and noise. Pollutant effects are discussed. Pollution control technologies that may be applicable are described along with preliminary cost estimates for their application. Finally discharge and emission limitations are suggested that may serve as interim guidance for pollution control during early geothermal development.
Date: June 1, 1978
Creator: Hartley, Robert P.
Partner: UNT Libraries Government Documents Department

Resistivity During Boiling in the SB-15-D Core from the Geysers Geothermal Field: The Effects of Capillarity

Description: In a laboratory study of cores from borehole SB-15-D in The Geysers geothermal area, we measured the electrical resistivity of metashale with and without pore-pressure control, with confining pressures up to 100 bars and temperatures between 20 and 150 C, to determine how the pore-size distribution and capillarity affected boiling. We observed a gradual increase in resistivity when the downstream pore pressure or confining pressure decreased below the phase boundary of free water. For the conditions of this experiment, boiling, as indicated by an increase in resistivity, is initiated at pore pressures of approximately 0.5 to 1 bar (0.05 to 0.1 MPa) below the free-water boiling curve, and it continues to increase gradually as pressure is lowered to atmospheric. A simple model of the effects of capillarity suggests that at 145 C, less than 15% of the pore water can boil in these rocks. If subsequent experiments bear out these preliminary observations, then boiling within a geothermal reservoir is controlled not just by pressure and temperature but also by pore-size distribution. Thus, it may be possible to determine reservoir characteristics by monitoring changes in electrical resistivity as reservoir conditions change.
Date: January 1, 1997
Creator: Roberts, J.; Duba, A.; Bonner, B. & Kasameyer, P.
Partner: UNT Libraries Government Documents Department