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Experimental and Theoretical Studies of Liquid Injection into Vapour-Dominated Reservoirs

Description: We analyze the injection of liquid into a depleted geothermal reservoir using numerical, analytical and experimental techniques. We first investigate the injection of liquid at the base of a uniformly heated reservoir and show how an ascending liquid layer develops. Ahead of the liquid-vapor interface the temperature rises sharply and, for cases in which the permeability is sufficiently high, the vapor is approximately isobaric. The region immediately behind the advancing liquid-vapor interface is approximately isothermal and therefore, the fraction vaporizing is dependent on the reservoir superheat. When the reservoir is overlain by a supercooled zone, some of the vapor produced at the ascending liquid-vapor interface condenses. As a result, the amount of newly formed vapor available for subsequent extraction can be significantly reduced.
Date: January 1, 1995
Creator: Fitzgerald, S.D. & Woods, W.
Partner: UNT Libraries Government Documents Department

Pressure-Temperature-Spinner Survey in a Well at the Geysers

Description: This paper presents results from a flowing pressure-temperature-spinner log run in a well drilled by GEO Operator Corporation (GEOOC) at The Geysers. Analysis and interpretation of the log data are also presented. The data indicated superheated steam with a temperature of 600 F (316 C) and an enthalpy of 1316 BTU/lbm (725 cal/gm) entered the wellbore below 8000 feet (2438 meters). This temperature and enthalpy is much higher than most Geysers steam wells which produce steam at or below 475 F (246 C) and 1240 BTU/lbm (683 CALIgm). The high temperature and enthalpy are even more puzzling since static pressure and temperature measurements conducted with Kuster type instruments six months later, indicate a ''normal'' vapor-dominated system existing at 475 F (246 C) and 500 psia (35 Kg/cm{sup 2}). Conceptual reservoir models which can explain these unusual thermodynamic conditions are presented.
Date: January 21, 1986
Creator: Drenick, Andy
Partner: UNT Libraries Government Documents Department

Decline curve analysis of vapor-dominated reservoirs

Description: Geothermal Program activities at the INEEL include a review of the transient and pseudosteady state behavior of production wells in vapor-dominated systems with a focus on The Geysers field. The complicated history of development, infill drilling, injection, and declining turbine inlet pressures makes this field an ideal study area to test new techniques. The production response of a well can be divided into two distinct periods: transient flow followed by pseudo-steady state (depletion). The transient period can be analyzed using analytic equations, while the pseudo-steady state period is analyzed using empirical relationships. Yet by reviewing both periods, a great deal of insight can be gained about the well and reservoir. An example is presented where this approach is used to determine the permeability thickness product, kh, injection and production interference, and estimate the empirical Arps decline parameter b. When the production data is reinitialized (as may be required by interference effects), the kh determined from the new transient period is repeatable. This information can be used for well diagnostics, quantification of injection benefits, and the empirical estimation of remaining steam reserves.
Date: May 1, 1997
Creator: Faulder, D.D.
Partner: UNT Libraries Government Documents Department

Stanford geothermal program. Final report, July 1990--June 1996

Description: This report discusses the following: (1) improving models of vapor-dominated geothermal fields: the effects of adsorption; (2) adsorption characteristics of rocks from vapor-dominated geothermal reservoir at the Geysers, CA; (3) optimizing reinjection strategy at Palinpinon, Philippines based on chloride data; (4) optimization of water injection into vapor-dominated geothermal reservoirs; and (5) steam-water relative permeability.
Date: March 1, 1998
Partner: UNT Libraries Government Documents Department

Quantitative model of vapor dominated geothermal reservoirs as heat pipes in fractured porous rock

Description: We present a numerical model of vapor-dominated reservoirs which is based on the well-known conceptual model of White, Muffler, and Truesdell. Computer simulations show that upon heat recharge at the base, a single phase liquid-dominated geothermal reservoir in fractured rock with low matrix permeability will evolve into a two-phase reservoir with B.P.D. (boiling point-for-depth) pressure and temperature profiles. A rather limited discharge event through cracks in the caprock, involving loss of only a few percent of fluids in place, is sufficient to set the system off to evolve a vapor-dominated state. The attributes of this state are discussed, and some features requiring further clarification are identified. 26 refs., 5 figs.
Date: March 1, 1985
Creator: Pruess, K.
Partner: UNT Libraries Government Documents Department

Stanford Geothermal Program [quarterly technical report, October--December 1991]

Description: Progress is reported on the following: experimental measurements of steam adsorption, estimation of adsorption parameters from experimental and field data, analysis of adsorption and desorption during injection into vapor-dominated reservoirs, and analyzing multiwell pressure data. (MHR)
Date: March 9, 1992
Partner: UNT Libraries Government Documents Department

Stanford Geothermal Program [quarterly technical progress reports, July--September 1990 and October--December 1990]

Description: For the summer quarter, progress is summarized and data are presented on the following: well test analysis of finite-conductivity fractures, theoretical investigation of adsorption phenomena, and optimization of reinjection strategy. For the fall quarter, activity focused on the adsorption and well testing projects. A new project investigating reinjection at the Geysers was initiated. (MHR)
Date: February 18, 1991
Partner: UNT Libraries Government Documents Department

Simulation of Radon Transport in Geothermal Reservoirs

Description: Numerical simulation of radon transport is a useful adjunct in the study of radon as an in situ tracer of hydrodynamic and thermodynamic numerical model has been developed to assist in the interpretation of field experiments. The model simulates transient response of radon concentration in wellhead geofluid as a function of prevailing reservoir conditions. The radon simulation model has been used to simulate radon concentration response during production drawdown and two flowrate transient tests in vapor-dominated systems. Comparison of model simulation with experimental data from field tests provides insight in the analysis of reservoir phenomena such as propagation of boiling fronts, and estimates of reservoir properties of porosity and permeability thickness.
Date: December 15, 1983
Creator: Semprini, Lewis & Kruger, Paul
Partner: UNT Libraries Government Documents Department

Geothermal Geophysical Research in Electrical Methods at UURI

Description: The principal objective of electrical geophysical research at UURI has been to provide reliable exploration and reservoir assessment tools for the shallowest to the deepest levels of interest in geothermal fields. Three diverse methods are being considered currently: magnetotellurics (MT, and CSAMT), self-potential, and borehole resistivity. Primary shortcomings in the methods addressed have included a lack of proper interpretation tools to treat the effects of the inhomogeneous structures often encountered in geothermal systems, a lack of field data of sufficient accuracy and quantity to provide well-focused models of subsurface resistivity structure, and a poor understanding of the relation of resistivity to geothermal systems and physicochemical conditions in the earth generally. In MT, for example, interpretation research has focused successfully on the applicability of 2-D models in 3-D areas which show a preferred structural grain. Leading computer algorithms for 2-D and 3-D simulation have resulted and are combined with modern methods of regularized inversion. However, 3-D data coverage and interpretation is seen as a high priority. High data quality in our own research surveys has been assured by implementing a fully remote reference with digital FM telemetry and real-time processing with data coherence sorting. A detailed MT profile across Long Valley has mapped a caldera-wide altered tuff unit serving as the primary hydrothermal aquifer, and identified a low-resistivity body in the middle crust under the west moat which corresponds closely with teleseismic delay and low density models. In the CSAMT method, our extensive tensor survey over the Sulphur Springs geothermal system provides valuable structural information on this important thermal regime and allows a fundamental analysis of the CSAMT method in heterogeneous areas. The self-potential (SP) method is promoted as an early-stage, cost-effective, exploration technique for covered hydrothermal resources, of low to high temperature, which has little or no adverse environmental impact ...
Date: March 24, 1992
Creator: Wannamaker, Philip E. & Wright, Phillip M.
Partner: UNT Libraries Government Documents Department

Evaluation of the Effects of Geothermal Reservoir Fluid Temperature on the Costs of Steam Production and Power Generation

Description: This report provides a preliminary evaluation of the effect of reservoir temperatures on the cost of geothermal hot water wells and flash-steam gathering systems to support a 50,000 kW power plant. Comparisons are made of the capital investments required for each case and the corresponding payout period based on steam costs of 6 mill/kWh of power generated. In order to show how the reservoir temperatures and steam cost affect the cost of electric power delivered to the high tension bus at the power plant, capital costs estimates were prepared and economic analyses made to determine the cost of electric power for each corresponding case.
Date: April 1, 1973
Partner: UNT Libraries Government Documents Department

Energy analysis of geothermal-electric systems

Description: 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 this conclusion. Vapor dominated, the only technology in current commercial use to produce electricity in the US, has the highest energy ratio (13 +- 4). These results for energy ratio are equal to or less than some from other workers. In the case of liquid dominated, environmental control technology has a considerable energy requirement.
Date: December 1, 1979
Creator: Herendeen, R.A. & Plant, R.
Partner: UNT Libraries Government Documents Department

Modeling studies of cold water injection into fluid-depleted, vapor-dominated geothermal reservoirs

Description: The physical processes involved in cold water injection into a ''superheated'' fractured reservoir are not yet fully understood, and this insufficient knowledge of the fundamental mechanisms limits the possibility of forecasting future resevoir behavior and optimizing the heat extraction process. Numerical simulation can be a very effective tool in the study of the complex phenomena involved, allowing a rapid examination of different situations and conditions, a systematic investigation of the effects of various parameters on reservoir performance, and some insight into long term behavior. We have performed simulation experiments on simple one-dimensional, porous and fractured reservoir models in order to study the migration of injected water, thermodynamic conditions in the boiling zone, heat extraction, and vapor generation. A two-dimensional radial porous medium model, with some characteristics typical of the high productivity zones of Larderello, has also been applied for studying the evolution of the shape and the thermodynamic conditions of the injection plume in the presence of gravity, reservoir heterogeneities and anisotropy.
Date: January 1, 1986
Creator: Calore, C.; Pruess, K. & Celati, R.
Partner: UNT Libraries Government Documents Department

Introduction to electric energy conversion systems for geothermal energy resources

Description: The types of geothermal energy conversion systems in use are classified as follows: direct, dry steam; separated steam; single-flash steam; double-flash steam; multi-flash steam; brine/Freon binary cycle; and brine/isobutane binary cycle. The thermodynamics of each of these is discussed with reference to simplified flow diagrams. Typical existing power plants are identified for each type of system. (MHR)
Date: June 1, 1978
Creator: DiPippo, R.
Partner: UNT Libraries Government Documents Department

Numerical simulation of the natural evolution of vapor-dominated hydrothermal systems

Description: Simulation of the transient evolution of a cold hydrothermal system into a steady-state partially vapor-dominated system is described. Here the effects of salts and gases were neglected and it was assumed that rock properties are time independent and homogeneous within each part of the system. Despite these simplifications it is believed that the model demonstrates the essential features of a natural hydrothermal convection system. (MHR)
Date: December 1, 1980
Creator: Pruess, K. & Truesdell, A.H.
Partner: UNT Libraries Government Documents Department

Reinjection studies of vapor-dominated systems

Description: The basic physical phenomena associated with geothermal injection are reviewed; problems associated with its numerical simulation are discussed; and the results of some numerical studies are presented. The particular problems chosen for study are: injection of cold water into a thin (single layer) reservoir; a five-spot production/injection configuration in a thin (single layer) reservoir; injection of cold water into a thick (multi-layer) reservoir; and injection of cold water into a one-dimensonal vertical column, representing a cross section of Larderello geothermal reservoir. (MHR)
Date: October 20, 1980
Creator: Schroeder, R.C.; O'Sullivan, M.J.; Pruess, K.; Celati, R. & Ruffilli, C.
Partner: UNT Libraries Government Documents Department

Geysers reservoir studies

Description: LBL is conducting several research projects related to issues of interest to The Geysers operators, including those that deal with understanding the nature of vapor-dominated systems, measuring or inferring reservoir processes and parameters, and studying the effects of liquid injection. All of these topics are directly or indirectly relevant to the development of reservoir strategies aimed at stabilizing or increasing production rates of non-corrosive steam, low in non-condensable gases. Only reservoir engineering studies will be described here, since microearthquake and geochemical projects carried out by LBL or its contractors are discussed in accompanying papers. Three reservoir engineering studies will be described in some detail, that is: (a) Modeling studies of heat transfer and phase distribution in two-phase geothermal reservoirs; (b) Numerical modeling studies of Geysers injection experiments; and (c) Development of a dual-porosity model to calculate mass flow between rock matrix blocks and neighboring fractures.
Date: April 1, 1993
Creator: Bodvarsson, G. S.; Lippmann, M. J. & Pruess, K.
Partner: UNT Libraries Government Documents Department

Geysers injection modeling

Description: Our research is concerned with mathematical modeling techniques for engineering design and optimization of water injection in vapor-dominated systems. The emphasis in the project has been on the understanding of physical processes and mechanisms during injection, applications to field problems, and on transfer of numerical simulation capabilities to the geothermal community. This overview summarizes recent work on modeling injection interference in the Southeast Geysers, and on improving the description of two-phase flow processes in heterogeneous media.
Date: April 1, 1994
Creator: Pruess, K.
Partner: UNT Libraries Government Documents Department

Gas geochemistry of the Geysers geothermal field

Description: Increases in gas concentrations in Central and Southeast Geysers steam are related to the decreases in pressure caused by heavy exploitation in the 1980s. When reservoir pressures in the central parts of the field decreased, high-gas steam from undrilled reservoir margins (and possibly from underlying high-temperature zones) flowed into exploited central areas. The Northwest Geysers reservoir probably lacks high-gas marginal steam and a decline in pressure may not cause a significant increase of gas concentrations in produced steam.
Date: April 1, 1993
Creator: Truesdell, A. H.
Partner: UNT Libraries Government Documents Department

Geothermal Research and Development Program. Quarterly technical report, September--December 1992

Description: Results are reported on adsorption of water vapor on reservoir rocks, physics of injection of water into vapor-dominated geothermal reservoirs, earth-tide effects on downhole pressures, injection optimization at the Geysers, effects of salinity in adsorption experiments, interpreting multiwell pressure data from Ohaaki, and estimation of adsorption parameters from transient experiments.
Date: January 25, 1993
Partner: UNT Libraries Government Documents Department

Geothermal research and development program. Quarterly technical report, July 1992--September 1992

Description: Progress is reported on the following projects: adsorption of water vapor on reservoir rocks, estimation of adsorption parameters from experimental data, heat of desorption and reservoir behavior, physics of injection into vapor-dominated reservoirs, earthtide effects on downhole pressures, and pressure transient and tracer test analysis in heterogeneous reservoirs.
Date: November 3, 1992
Partner: UNT Libraries Government Documents Department

Stanford Geothermal Program [quarterly technical report, April--June 1991; topical report, July 1, 1990--June 30, 1991]

Description: The reinjection task on optimizing injection into the Palinpinon geothermal field in the Philippines was completed. Progress is summarized on experimental investigation of absorption, estimation of adsorption parameters from experimental and field data, the theoretical study of adsorption isotherms, and interpreting pressure data. (MHR)
Date: July 16, 1991
Partner: UNT Libraries Government Documents Department

LBL research on The Geysers: Conceptual models, simulation and monitoring studies

Description: As part of The Geysers research activities of DOE`s Geothermal Reservoir Technology Program, LBL, in close co-operation with industry, is performing fundamental and applied studies of vapor- dominated geothermal systems. These studies include the development of new methods for evaluating cold water injection, monitoring of the seismic activity in The Geysers associated with injection and production, interpretation of pressure and geochemical changes measured during well tests and long-term production and injection operations, and improvement of existing models of the geothermal system. A review is given of the latest results of DOE-sponsored LBL reservoir engineering and seismic studies relevant to The Geysers.
Date: March 1, 1982
Creator: Bodvarsson, G. S.; Lippmann, M. J.; Majer, E. L. & Pruess, K.
Partner: UNT Libraries Government Documents Department

Development of a dual-porosity model for vapor-dominated fractured geothermal reservoirs using a semi-analytical fracture/matrix interaction term

Description: A new type of dual-porosity model is being developed to simulate two-phase flow processes in fractured geothermal reservoirs. At this time it is assumed that the liquid phase in the matrix blocks remains immobile. By utilizing the effective compressibility of a two-phase water/steam mixture in a porous rock, flow within the matrix blocks can be modeled by a single diffusion equation. This equation in turn is replaced by a non-linear ordinary differential equation that utilizes the mean pressure and mean saturation in the matrix blocks to calculate the rate of fluid flow between the matrix blocks and fractures. This equation has been incorporated into the numerical simulator TOUGH to serve as a source/sink term for computational gridblocks that represent the fracture system. The new method has been compared with solutions obtained using fully-discretized matrix blocks, on a problem involving a three-dimensional vapor-dominated reservoir containing an injection and a production well, and has been found to be quite accurate.
Date: February 1, 1993
Creator: Zimmerman, R. W.; Hadgu, T. & Bodvarsson, G. S.
Partner: UNT Libraries Government Documents Department