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Geothermal reservoir management

Description: The optimal management of a hot water geothermal reservoir was considered. The physical system investigated includes a three-dimensional aquifer from which hot water is pumped and circulated through a heat exchanger. Heat removed from the geothermal fluid is transferred to a building complex or other facility for space heating. After passing through the heat exchanger, the (now cooled) geothermal fluid is reinjected into the aquifer. This cools the reservoir at a rate predicted by an expression relating pumping rate, time, and production hole temperature. The economic model proposed in the study maximizes discounted value of energy transferred across the heat exchanger minus the discounted cost of wells, equipment, and pumping energy. The real value of energy is assumed to increase at r percent per year. A major decision variable is the production or pumping rate (which is constant over the project life). Other decision variables in this optimization are production timing, reinjection temperature, and the economic life of the reservoir at the selected pumping rate. Results show that waiting time to production and production life increases as r increases and decreases as the discount rate increases. Production rate decreases as r increases and increases as the discount rate increases. The optimal injection temperature is very close to the temperature of the steam produced on the other side of the heat exchanger, and is virtually independent of r and the discount rate. Sensitivity of the decision variables to geohydrological parameters was also investigated. Initial aquifer temperature and permeability have a major influence on these variables, although aquifer porosity is of less importance. A penalty was considered for production delay after the lease is granted.
Date: February 1, 1978
Creator: Scherer, C.R. & Golabi, K.
Partner: UNT Libraries Government Documents Department

Mathematical model of damage collars in water reinjection wells

Description: A recent study of the Imperial Magma-San Diego Gas and Electric Geothermal Experimental Site near Niland, California suggests that damage collar formation caused by deep invasion of water-borne particulates into the reinjection reservoir may be an important mechanism in water reinjection well performance. A model of damage collar effects has been developed and appears to provide insight which is consistent with information provided by other sources. For effective reinjection system analysis where damage collars are thought to exist, a more explicit understanding of the movement of water-borne particulates through porous media needs to be developed.
Date: May 1, 1978
Creator: Jorda, R.M.
Partner: UNT Libraries Government Documents Department

Mexican--American cooperative program at the Cerro Prieto Geothermal Field

Description: The Cerro Prieto project incorporates studies of the geologic, hydrogeologic, geochemical, and geophysical setting of the geothermal field as well as its structural, reservoir engineering, and subsidence characteristics. A description of the activities involved in each part of this cooperative program is presented. Text of the agreement between the Comision Federal de Electricidad of Mexico and the USERDA for the cooperative study of the Cerro Prieto geothermal field is included.
Date: August 1, 1978
Creator: Witherspoon, P.A.; Espinosa, H.A.; Lippmann, M.J.; Mercado, A.M. & Wollenberg, H.A.
Partner: UNT Libraries Government Documents Department

Geothermal pilot study final report: creating an international geothermal energy community

Description: The Geothermal Pilot Study under the auspices of the Committee on the Challenges of Modern Society (CCMS) was established in 1973 to apply an action-oriented approach to international geothermal research and development, taking advantage of the established channels of governmental communication provided by the North Atlantic Treaty Organization (NATO). The Pilot Study was composed of five substudies. They included: computer-based information systems; direct application of geothermal energy; reservoir assessment; small geothermal power plants; and hot dry rock concepts. The most significant overall result of the CCMS Geothermal Pilot Study, which is now complete, is the establishment of an identifiable community of geothermal experts in a dozen or more countries active in development programs. Specific accomplishments include the creation of an international computer file of technical information on geothermal wells and fields, the development of studies and reports on direct applications, geothermal fluid injection and small power plants, and the operation of the visiting scientist program. In the United States, the computer file has aready proven useful in the development of reservoir models and of chemical geothermometers. The state-of-the-art report on direct uses of geothermal energy is proving to be a valuable resource document for laypersons and experts in an area of increasing interest to many countries. Geothermal fluid injection studies in El Salvador, New Zealand, and the United States have been assisted by the Reservoir Assessment Substudy and have led to long-range reservoir engineering studies in Mexico. At least seven small geothermal power plants are in use or have been planned for construction around the world since the Small Power Plant Substudy was instituted--at least partial credit for this increased application can be assigned to the CCMS Geothermal Pilot Study. (JGB)
Date: June 1, 1978
Creator: Bresee, J.C.; Yen, W.W.S. & Metzler, J.E. (eds.)
Partner: UNT Libraries Government Documents Department

Analytic study of geothermal reservoir pressure response to cold water reinjection

Description: Derivation of the governing equation, including temperature effects, is given where the permeability-viscosity ratio is assumed to be an arbitrary function of r{sup 2}t. This function is represented by a Fermi-Dirac function, whose parameters are determined based upon physical considerations. The solution for the pressure change is analytic except for the final step, where a numerical integration is called for. The results and implications of the calculations are discussed. Summary and concluding remarks are presented.
Date: November 1, 1978
Creator: Tsang, Y.W. & Tsang, C.F.
Partner: UNT Libraries Government Documents Department

Stimulation and reservoir engineering of geothermal resources. First annual report, June 1, 1977-March 31, 1978

Description: The large geothermal reservoir model has been used to investigate the specific energy extraction capabilities of various production methods and to determine the rate of heat loss from various rock formations. A parallel laboratory and field study in radon analysis is described. In order to quantify the emission rates of radon from reservoir rocks, an experimental apparatus is under construction to provide exact information on the temperature, pressure, and rock property dependence of the radon production. Laboratory cores were used in bench-scale experiments to determine steam/water relative permeability curves for permeable formation; to investigate the property of vapor pressure lowering of water confined in porous media at low saturations; and to determine the effects of high confining pressures and temperatures on the absolute permeability of porous rocks. The well test analysis and educatonal programs are reported. (MHR)
Date: April 1, 1978
Creator: Kruger, P. & Ramey, H.J. Jr.
Partner: UNT Libraries Government Documents Department

Geothermal R and D project report for April 1, 1977--September 30, 1977

Description: The Idaho Geothermal Research and Development Program was initiated in 1973. The program's mission has been to improve the technology necessary to utilize geothermal fluids of moderate temperature--fluids of about 150/sup 0/C or 300/sup 0/F. This report discusses the progress from April to September 1977, during which time an injection well was drilled and the design of a 5000-kW(e) pilot power plant was completed. Manufacturers began fabricating heat exchangers and condensers for the power plant and a cooling tower to dissipate 40 MW of heat was ordered.
Date: March 1, 1978
Creator: Kunze, J. F.
Partner: UNT Libraries Government Documents Department

Studies of Flow Problems With the Simulator shaft78

Description: In recent years, a number of numerical simulators for geothermal reservoirs have been developed. The general purpose of these is to aid reservoir engineers in (i) determining characteristic parameters of reservoirs (most important among those being the reserves of fluid and heat), and (ii) simulating the performance of reservoirs upon production and injection. The various simulators differ in the approximations made in the underlying physical model (e.g., dependence of rock and fluid properties upon thermodynamic variables), in the geometrical definition of the reservoir (one-, two-, or three-dimensional, regular or irregular shape); in the choice of thermodynamic variables, and in the mathematical techniques used for solving the coupled mass and energy transport equations. Criteria for desirable performance of numerical simulators depend in part upon the particular problems to be investigated. Different problems will often differ in the required level of detail to be resolved, and in the optimum balance of speed and accuracy of computation. Much can be learned about two-phase flow in porous media from model studies for idealized systems. Such studies can be performed with less-than-three-dimensional model and algorithms which are based on regular grid spacings will be perfectly acceptable. For modeling natural geothermal reservoirs, on the other hand, it is important that irregular three-dimensional geometries may be handled easily. In comparison with other two-phase simulators which have been discussed in the literature, the main distinctive feature of SHAFT78 is that it uses an integrated finite difference method (IFD). We solve finite difference equations that are obtained by integrating the basic partial differential equations for mass and energy flow over discrete surface and volume elements. This method is as easily applicable to irregular geometries of actual reservoirs as it is to idealized, regular geometries; yet the relative simplicity of the finite difference method is retained in the theory and ...
Date: November 1, 1978
Creator: Pruess, K.; Schroeder, R. C. & Zerzan, J.
Partner: UNT Libraries Government Documents Department

Hawaii Geothermal Project; HGP-A Reservoir Engineering

Description: The Hawaii Geothermal Project well HGP-A has undergone a two-year testing program which included cold water pumpdown tests, flashing flows with measurements of temperature and pressure profiles, and noise surveys. These tests and the data obtained are discussed in detail.
Date: September 1, 1978
Creator: Yuen, P.C.; Chen, B.H.; Kihara, D.H.; Seki, A.S. & Takahashi, P.K.
Partner: UNT Libraries Government Documents Department

Areas of ground subsidence due to geofluid withdrawal

Description: Detailed information is provided on four geothermal areas with histories of subsidence. These were selected on the basis of: physical relevance of subsidence areas to high priority US geothermal sites in terms of withdrawn geofluid type, reservoir depth, reservoir geology and rock characteristics, and overburden characteristics; and data completeness, quality, and availability. The four areas are: Chocolate Bayou, Raft River Valley, Wairakei, and the Geysers. (MHR)
Date: August 1, 1978
Creator: Grimsrud, G.P.; Turner, B.L. & Frame, P.A.
Partner: UNT Libraries Government Documents Department

Geothermal Loop Experimental Facility. Quarterly report, April--June 1978

Description: The Geothermal Loop Experimental Facility (GLEF) was modified to use a two stage flash process with two parallel flash trains for the extraction of energy from a high temperature, high salinity, liquid-dominated resource. Since plant start-up in May 1976, a substantial amount of information has been obtained on the operation of the plant, components, brine and steam composition, production and injection wells, and the potential of the Niland Reservoir. The general operation and accomplishments of the GLEF during the period April 1978 through June 1978 are discussed. The GLEF underwent a major redesign. Modifications and inspections of various GLEF equipment and systems are also discussed. Information about the production and injection wells flow testing and instrumentation are discussed. Information regarding coatings and linings for valves and piping is included. In the Chemistry Section there is a wide range of data taken from Brine, Steam, Scale, Binary, Condensate, and Cooling Water Systems.
Date: July 1, 1978
Creator: Bischoff, W.S.; Bishop, H.K.; Cooney, C.S.; Hanenburg, W.H.; Hoaglin, G.J.; Jacobson, W.O. et al.
Partner: UNT Libraries Government Documents Department

Simulation and optimization of hot dry rock geothermal energy conversion systems: process conditions and economics

Description: The Los Alamos Scientific Laboratory is currently engaged in a field program aimed at designing and testing man-made geothermal reservoirs in hot granitic formations of low permeability created by hydraulic fracturing. A very important segment of the program is concerned with defining and optimizing several parameters related to the performance of the reservoir and their impact on the potential commercial feasibility of the hot dry rock technique. These include effective heat transfer area, permeation water loss, depth to the reservoir, geothermal temperature gradient, reservoir temperature, mass flow rate, and geochemistry. In addition, the optimization of the energy end use system (process or district heating, electricity or cogeneration) is directly linked to reservoir performance and associated costs. This problem has been studied using several computer modeling approaches to identify the sensitivity of the cost of power to reservoir and generation plant parameters. Also examined were a variety of important economic elements including rate of return on invested capital, discount or interest rates, taxes, cash flow, energy selling price, plant and reservoir lifetime, drilling and surface plant costs, and royalties.
Date: January 1, 1978
Creator: Tester, J.W.
Partner: UNT Libraries Government Documents Department

Evaluation of the Fenton Hill Hot Dry Rock Geothermal Reservoir. Part I. Heat extraction performance and modeling. Part II. Flow characteristics and geochemistry. Part III. Reservoir characterization using acoustic techniques

Description: On May 28, 1977, as the production well GT-2 at Fenton Hill was being redrilled along a planned trajectory, it intersected a low-impedance hydraulic fracture in direct communication with the injection well, EE-1. Thus, a necessary prerequisite for a full-scale test of the LASL Hot Dry Rock Concept, that of establishing a high flow rate between wells at low wellhead differential pressures, was satisified. Full-scale operation of the loop occurred for 75 days from January 27 to April 12, 1978. This test is referred to as Phase 1, Segment 2 and was designed to examine the thermal drawdown, flow characteristics, water losses, and fluid geochemistry of the system in detail. Results of these studies are the major topic of this paper which is divided into three separate parts covering first the heat extraction performance, second the flow characteristics and geochemistry and third the use of acoustic techniques to describe the geometry of the fracture system. In the third section, dual-well acoustic measurements used to detect fractures are described. These measurements were made using modified Dresser Atlas logging tools. Signals intersecting hydraulic fractures in the reservoir under both hydrostatic and pressurized conditions were simultaneously detected in both wells. Signal attenuation and characteristic waveforms can be used to describe the extent of fractured rock in the reservoir.
Date: January 1, 1978
Creator: Murphy, H.D.; Grigsby, C.O.; Tester, J.W. & Albright, J.N.
Partner: UNT Libraries Government Documents Department

Preliminary reservoir and subsidence simulations for the Austin Bayou geopressured geothermal prospect

Description: For the last several years, the University of Texas at Austin (UTA) has analyzed the geopressured tertiary sandstones along the Texas Gulf Coast with the objective of locating prospective reservoirs from which geothermal energy could be recovered. Of the ''geothermal fairways'' (areas with thick sandstone bodies and estimated temperatures in excess of 300 F), the Brazoria fairway appears most promising and the Austin Bayou Prospect has been developed within this fairway. A test well (DOE 1 Martin Ranch) is currently being drilled in this area. Pending the availability of actual well test data, estimated reservoir properties have been employed in numerical simulations to study the effects of variations in reservoir properties on the projected long-term behavior of the Austin Bayou Prospect. The simulations assess the sensitivity of the reservoir behavior to variations is estimated sandstone/shale distribution, shale compressibility, and vertical shale permeability. Further, hypothetical properties for the stress-deformation behavior of the rock formations were employed in a very preliminary study of the potential ground surface displacements that might accompany fluid production.
Date: January 1, 1978
Creator: Garg, S.K.; Riney, T.D. & Brownell, D.H., Jr.
Partner: UNT Libraries Government Documents Department

Testing, planning, and redrilling of Geothermal Test Hole GT-2, Phases IV and V. Progress report

Description: Holes GT-2 and EE-1 comprise the two deep drill holes of the Los Alamos Hot Dry Rock Geothermal Energy Extraction Experiment. EE-1 had been directionally drilled to intersect a hydraulic fracture extending outward from near the bottom of GT-2, thus completing the underground circulation loop. After the drilling of EE-1, a 16-month period of experimental testing ensued to determine the characteristics of the reservoir. This period is designated as Phase IV and includes work done in GT-2 and EE-1. As a result of this testing, it was determined that parallel fracture zones existed at the bottoms of both holes, and that the impedance to flow between the holes was too high for a meaningful flow experiment. A plan was then adopted to directionally drill out of GT-2 at a depth of about 2600 m (8500 ft) to intersect the fracture zone near the bottom of EE-1 to create a better connection. The directional drilling strategy, cementing practices, bit selections, coring procedures, and logging results comprise the Phase V work.
Date: December 1978
Creator: Pettitt, R. A.
Partner: UNT Libraries Government Documents Department

Downhole measurements and fluid chemistry of a Castle Rock steam well, The Geysers, Lake County, California

Description: Certain wells within The Geysers steam field have standing water columns either when first drilled or when produced at low flow rates. These water columns have been attributed by Lipman et al. (1978) to accumulation of water condensing in the well bore. Alternative explanations are that perched water bodies exist within the reservoir or that a deep water body underlying the steam reservoir has been tapped. A well in the Castle Rock field of The Geysers drilled by Signal Oil and Gas Company (now Aminoil, U.S.A.) with such a water column was sampled in 1976 for water, gas, and isotope chemistry in hopes of distinguishing between these possible origins; the results along with the well history and downhole pressure and temperature measurements are reported here. The well is located in Lake County, California, in the central part of the Castle Rock field, 4.8 km west-northwest of the town of Anderson Springs. Drilling was started in mid 1970 on a ridge at an elevation of 700 m above sea level. Steam entries were encountered at depths (below land surface) of 1,899, 1,902, 2,176, 2,248 2,288, and 2,295 m; the total depth drilled was 2,498 m. Large volume water entries above 685 m were cased off to 762 m.
Date: January 1, 1978
Creator: Truesdell, Alfred H.; Frye, George A. & Nathenson, Manuel
Partner: UNT Libraries Government Documents Department

The effect of thermal conduction upon pressure drawdown and buildup in fissured, vapor-dominated geothermal reservoirs

Description: An analysis of steam-pressure behavior in a vapor-dominated geothermal reservoir with an immobile vaporizing liquid phase was presented by Moench and Atkinson (1977) at the Third Stanford Workshop on Geothermal Reservoir Engineering, and later expanded by Moench and Atkinson (1978). In that study a finite-difference model was used to demonstrate the effects of phase change in the reservoir upon pressure drawdown and buildup. In this paper that model is modified to incorporate heat transfer from blocks of impermeable rock to thin, highly-permeable, porous fissures. The purpose of this study is to demonstrate the added effect of heat transfer of this type upon the transient pressure response of a vapor-dominated geothermal reservoir.
Date: January 1, 1978
Creator: Moench, A.F.
Partner: UNT Libraries Government Documents Department

Formation plugging while testing a steam well at The Geysers

Description: During testing of a steam well at The Geysers steam field in Sonoma County, California, rate suddenly dropped by 17,500 lb/hr and wellhead pressure simultaneously increased by 30 psi. There was no evidence of plugging in any of the surface facilities downstream of the wellhead. Pressure buildup tests before and after the incident show that there was a 15% reduction in permeability-thickness. Analysis of pressure losses in the wellbore due to friction showed that all of the rise in wellhead pressure could be explained by the reduction in mass flow that occurred as a result of the 15% reduction in kh. The change in wellhead enthalpy from 1200 Btu/lb and 4-5 F superheat prior to the incident to 1197 Btu/lb and 0-1.4 F superheat after the incident indicates the well became slightly wet. One possible explanation for this reduction in kh is that movement of free water caused a plugging action or a reduction of mobility to steam in one or more steam entries.
Date: January 1, 1978
Creator: Strobel, Calvin J.
Partner: UNT Libraries Government Documents Department

Geothermal reservoir testing based on signals of tidal origin

Description: The theory of pressure and water level oscillations of tidal origin in Darcy type aquifers and petroleum reservoirs has been discussed in a number of recent publications. There is a general agreement that observational data on the tidal pressure phenomena may be applied to obtain useful estimates of important reservoir parameters such as the permeability.
Date: January 1, 1978
Creator: Bodvarsson, Gunnar & Hanson, Jonahthan
Partner: UNT Libraries Government Documents Department

Geothermal reservoir engineering research in New Zealand: A simplistic model and the Wairakei geothermal reservoir

Description: Although nowadays much of the New Zealand geothermal reservoir research effort is still being concentrated on the older fields of Wairakei and Broadlands there has been a definite advance over recent years in our approach to the studies. On the practical side, long term reinjection trials are now in progress at Broadlands, and drilling, for field evaluation, is well underway at Ngawha, a field characterized by a steam discharge coupled with a hydrostatic pressure gradient. On the theoretical side, well pressure transient analysis and reservoir behavior modeling are probably the primary interests. For the former both multi-element computer modeling programs and two-phase pressure diffusion analysis (Grant, 1978, Grant and Sorey, 1979) are being used by M.A.Grant, E.Bradford and F.Sutton (AMD*) and M.L.Sorey (PEL). Geometry and boundary influences are dominant and estimated steam flows are higher than are consistent with the Corey (1954) expressions for relative permeability. Both of these effects are probably due to the fracture permeability of the reservoirs. A.McNabb (AMD) is currently taking this into account by determining the response to discharge in a fracture-block medium. He is working with 100 meter blocks, consistent with data from lumped parameter models and from well records, with a block permeability of 10{sup -15} m{sup 2}. Reservoir behavior modeling is probably the research area of greatest current interest with most research groups here involved to some extent. The models range over a wide spectrum, from extreme simplification to sophisticated detail. At the simpler extreme is the model of J.Elder (AU). This consists of two resistors and a condenser in electrical analog form but is coupled with models of the well system and the above surface plant to enable overall system effects and interactions to be assessed.
Date: January 1, 1978
Creator: Donaldson, Ian G.
Partner: UNT Libraries Government Documents Department

Simulation of the Broadlands geothermal field, NZ

Description: The governing equations for a two phase geothermal reservoir are presented for the case when a substantial amount of carbon dioxide is present. Sample results for a model reservoir based on the Broadlands geothermal field are given.
Date: January 1, 1978
Creator: Zyvolski, G. A. & O'Sullivan, M. J.
Partner: UNT Libraries Government Documents Department

Results of well-testing in the Broadlands geothermal field, New Zealand

Description: Although not the first hot-water geothermal field under development, the Broadlands geothermal field has shown itself to be quite different in behavior to other hot-water fields. The field was discharged some five years between 1966 and 1971, and has provided a large source of data in its as yet undeveloped state. This paper presents some of the results inferred from well-testing and highlights (1) the complexity of the system, (2) the importance of wellbore storage effects and (3) the effects of reinjection.
Date: January 1, 1978
Creator: Horne, Roland N.; Grant, Malcolm A. & Gale, Robert O.
Partner: UNT Libraries Government Documents Department