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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

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

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

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

Effects of capillarity and vapor adsorption in the depletion of vapor-dominated geothermal reservoirs

Description: Vapor-dominated geothermal reservoirs in natural (undisturbed) conditions contain water as both vapor and liquid phases. The most compelling evidence for the presence of distributed liquid water is the observation that vapor pressures in these systems are close to saturated vapor pressure for measured reservoir temperatures (White et al., 1971; Truesdell and White, 1973). Analysis of natural heat flow conditions provides additional, indirect evidence for the ubiquitous presence of liquid. From an analysis of the heat pipe process (vapor-liquid counterflow) Preuss (1985) inferred that effective vertical permeability to liquid phase in vapor-dominated reservoirs is approximately 10{sup 17} m{sup 2}, for a heat flux of 1 W/m{sup 2}. This value appears to be at the high end of matrix permeabilities of unfractured rocks at The Geysers, suggesting that at least the smaller fractures contribute to liquid permeability. For liquid to be mobile in fractures, the rock matrix must be essentially completely liquid-saturated, because otherwise liquid phase would be sucked from the fractures into the matrix by capillary force. Large water saturation in the matrix, well above the irreducible saturation of perhaps 30%, has been shown to be compatible with production of superheated steam (Pruess and Narasimhan, 1982). In response to fluid production the liquid phase will boil, with heat of vaporization supplied by the reservoir rocks. As reservoir temperatures decline reservoir pressures will decline also. For depletion of ''bulk'' liquid, the pressure would decline along the saturated vapor pressure curve, while for liquid held by capillary and adsorptive forces inside porous media, an additional decline will arise from ''vapor pressure lowering''. Capillary pressure and vapor adsorption effects, and associated vapor pressure lowering phenomena, have received considerable attention in the geothermal literature, and also in studies related to geologic disposal of heat generating nuclear wastes, and in the drying of porous materials. Geothermally ...
Date: January 1, 1992
Creator: Pruess, Karsten & O'Sullivan, Michael
Partner: UNT Libraries Government Documents Department

Lassen geothermal system

Description: 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.
Date: January 1, 1982
Creator: Muffler, L.J.P.; Nehring, N.L.; Truesdell, A.H.; Janik, C.J.; Clynne, M.A. & Thompson, J.M.
Partner: UNT Libraries Government Documents Department

Geothermal progress monitor: Report No. 17

Description: DOE is particularly concerned with reducing the costs of geothermal power generation, especially with the abundant moderate to low-temperature resources in the US. This concern is reflected in DOE`s support of a number of energy conversion projects. Projects which focus on the costs and performance of binary cycle technology include a commercial demonstration of supersaturated turbine expansions, which earlier studies have indicated could increase the power produced per pound of fluid. Other binary cycle projects include evaluations of the performance of various working fluid mixtures and the development and testing of advanced heat rejection systems which are desperately needed in water-short geothermal areas. DOE is also investigating the applicability of flash steam technology to low-temperature resources, as an economic alternative to binary cycle systems. A low-cost, low-pressure steam turbine, selected for a grant, will be constructed to utilize fluid discharged from a flash steam plant in Nevada. Another project addresses the efficiency of high-temperature flash plants with a demonstration of the performance of the Biphase turbine which may increase the power output of such installations with no increase in fluid flow. Perhaps the most noteworthy feature of this issue of the GPM, the 17th since its inception in 1980, is the high degree of industry participation in federally-sponsored geothermal research and development. This report describes geothermal development activities.
Date: December 1, 1995
Partner: UNT Libraries Government Documents Department

History match simulation of Serrazzano geothermal reservoir

Description: The simulator SHAFT79 of Lawrence Berkeley Laboratory has been applied to field-wide distributed parameter simulation of the vapor-dominated geothermal reservoir at Serrazzano, Italy. Using a three-dimensional geologically accurate mesh and detailed flow rate data from 19 producing wells, a period of 15.5 years (from 1959 to 1975) has been simulated. The reservoir model used is based on field measurements of temperatures and pressures, laboratory data for core samples, and available geological and hydrological information. The main parameters determined (adjusted) during development of the simulation are permeabilities and much of the initial conditions. Simulated patterns of pressure decline show semi-quantitative agreement with field observations. The simulation suggests that there is cold water recharge and/or incomplete heat transfer from he rock due to fractures in the margins of the reservoir, and some steam flowing to the main well field originates from deep fractures rather than from boiling in the two-phase zones modeled. Simulation methodology and ambiguity of parameter determination is discussed.
Date: August 1, 1980
Creator: Pruess, K.; Weres, O.; Schroeder, R.; Marconcini, R. & Neri, G.
Partner: UNT Libraries Government Documents Department

Numerical studies of the energy sweep in five-spot geothermal production/injection systems

Description: The present work is aimed at helping to improve the qualitative and quantitative understanding of injection into a geothermal reservoir by considering a few idealized problems. First a vapor-dominated, single layer reservoir is considered, next a vapor-dominated, four layer reservoir, and finally a liquid-dominated, single layer reservoir. In each case varying injection rates are considered and in some cases the injection is changed at different times. The SHAFT9 simulator is used to calculate the reservoir behavior in each case. The calculations are made for a five-spot configuration of alternate, off-set rows of producers and injectors. A calculation mesh with 34 nodes is used, which is barely sufficient to give accurate results. In fact, some of the results exhibit small oscillations with time due to this relatively coarse discretization. (MHR)
Date: December 1, 1980
Creator: O'Sullivan, M.J. & Pruess, K.
Partner: UNT Libraries Government Documents Department

Well-bore effects in the analysis of two-phase geothermal well tests

Description: A method of designing and analyzing pressure transient well tests of two-phase (steam-water) reservoirs is given. Wellbore storage is taken into account and the duration of it is estimated. It is shown that the wellbore flow can completely dominate the downhole pressure signal such that large changes in the downhole pressure that might be expected because of changes in kinematic mobility are not seen. Changes in the flowing enthalpy from the reservoir can interact with the wellbore flow so that a temporary plateau in the downhole transient curve is measured. Application of graphical and non-graphical methods to determine reservoir parameters from drawdown tests is demonstrated.
Date: January 1, 1981
Creator: Miller, C.W.; Benson, S.; O'Sullivan, M.J. & Pruess, K.
Partner: UNT Libraries Government Documents Department

Recommendations for a US geothermal research plan. Volume 1

Description: A multidisciplinary study team developed a comprehensive research program. Five- and ten-year program plans emphasize critical five-year milestones. Recommended plans are presented here under constraint of three different five-year budgets: $100, $300 and $500 million, respectively. Plans are detailed in six resource subprograms: high temperature water, moderate temperature water, hot dry rock, brine, geopressured, and dry steam. Also presented are plans for five subprograms common to all geothermal resources: exploration, assessment, drilling technology, environmental-social, and institutional. (MHR)
Date: December 1, 1975
Creator: Burnham, J.B.; Bloomster, C.H.; Cohn, P.D.; Eliason, J.R.; Peterson, P.L.; Rohrmann, C.A. et al.
Partner: UNT Libraries Government Documents Department

High-temperature explosive development for geothermal well stimulation. Final report

Description: A two-component, temperature-resistant liquid explosive called HITEX has been developed which is capable of withstanding 561/sup 0/K (550/sup 0/F) for 24 hours in a geothermal environment. The explosive is intended for the stimulation of nonproducing or marginally producing geothermal (hot dry rock, vapor-dominated or hydrothermal) reservoirs by fracturing the strata in the vicinity of a borehole. The explosive is inherently safe because it is mixed below ground downhole from two nondetonable liquid components. Development and safety tests included differential scanning calorimetry, thermal stability, minerals compatibility, drop-weight sensitivity, adiabatic compression, electrostatic discharge sensitivity, friction sensitivity, detonation arrest capability, cook-off tests, detonability at ambient and elevated pressure, detonation velocity and thin film propagation in a wedge.
Date: March 31, 1978
Creator: Schmidt, E.W.; Mars, J.E. & Wang, C.
Partner: UNT Libraries Government Documents Department

Tenth workshop on geothermal reservoir engineering: proceedings

Description: The workshop contains presentations in the following areas: (1) reservoir engineering research; (2) field development; (3) vapor-dominated systems; (4) the Geysers thermal area; (5) well test analysis; (6) production engineering; (7) reservoir evaluation; (8) geochemistry and injection; (9) numerical simulation; and (10) reservoir physics. (ACR)
Date: January 22, 1985
Partner: UNT Libraries Government Documents Department