Work during the period included analytic studies of vent clearing and jet-slug dynamics and computer simulations (HEMP and CHAMP codes) of pressure suppression experiments.

The purpose of this test was to demonstrate that the alternator stator has satisfactorily completed sufficient testing to safisfy the requirements set forth within the Kilowatt Isotope Power System (KIPS) Component Test Specification for the GDS Alternator Stator (TS 2538). The results of the acceptance tests conducted on the alternator stator, S/N 003, are presented, and show that the stator did meet specified requirements.

Document issued by the Office of the Attorney General of Texas in Austin, Texas, providing an interpretation of Texas law. It provides the opinion of the Texas Attorney General, John L. Hill, regarding a legal question submitted for clarification; Computation of benefits due to State employee with a specific injury under the workmen's compensation statutes.

Precision gravity methods provide new information regarding geothermal reservoir mechanisms and depletion. This paper discusses the principles of present interpretations and early conclusions from two producing geothermal fields, Wairakei, in New Zealand, and The Geysers, California. 4 refs., 4 figs.

This paper is concerned with the optimal time to commence extraction of energy from a hot-water geothermal reservoir. The economic models that we have presented in the past have the common characteristics that the extraction program starts immediately (see References 1 and 2). Based on this assumption, we determined optimal extraction strategies and planning horizons such that the present values of total profits were maximized. In this study we relax the requirement that extraction be undertaken immediately, seeking instead the delay in starting time that along with the other decision variables maximizes the present value of total profits over the economic life of the reservoir. Of course, optimal starting time, economic life of the reservoir, optimal extraction rate, and optimal injection temperature are interrelated, and therefore, we analyze their effect on the overall planning strategy simultaneously. 4 refs.

Work over the past year has concentrated on three areas: 1) to implement a concept of vertical equilibrium in geothermal modeling, 2) to improve the matrix equation solution technique for both two- and three-dimensional models, which improvements this report describes in detail, and 3) to apply a vertical equilibrium, areal model to the Wairakei, New Zealand geothermal field. The steady-state modeling indicates that large regions in the reservoir probably had a small steam cap prior to exploitation. Furthermore, transient simulations indicate that leakage into the reservoir is significant; that is, the Wairakei reservoir is not a closed system. The most difficult part of history matching at Wairakei is adjusting permeabilities in order to remove enough mass from storage (as opposed to leakage) and reproduce the observed pressure decline trends. 5 refs.

The experimental well, HGP-A, drilled under the auspices of the Hawaii Geothermal Project, is located on the island of Hawaii near the eastern rift of Kilauea volcano. Drilling was completed to a depth of 6450 feet in April 1976. The well is cased to 2230 feet below the surface, which is 600 feet above sea level, with a slotted liner running from the end of the casing to bottomhole. Cuttings and core samples obtained during drilling indicate that the region is composed of volcanic basalt with a profile that contains a zone of open fractures (3300-4500 feet) and a zone of partially sealed fractures (4500-6450 feet) as shown in Figure 1. Conclusions from preliminary test results and analyses: the Kapho Geothermal Reservoir is liquid-dominated, with permeability thickness of ~ 1000 md-ft, very high temperatures ~ 350°C, high formation pressure ~ 2000 psi, slightly brackish water, and high silica content, and is potentially large; the HGP-A Geothermal Well borehole contains steam and water at saturation during flash; flashing occurs in formation; the well has high wellhead pressures ~ 160 psi at 50 Klb/hr steam, probably has severe skin damage, and potential power output ~ 3.5 MWe; the well’s producing regions are …

A well interference testing program of the Salton Sea Geothermal reservoir is being conducted as part of a resource evaluation study by the Earth Sciences Geothermal Industrial Support Program of the Lawrence Livermore Laboratory. Studies to date indicate the reservoir rock to be composed of layered sequences of shales and sands. Wells involved in the testing program are being used in support of, or are in the vicinity of, the MAGMA-SDG&E Geothermal Loop Experimental Facility (GLEF), located in the Salton Sea Geothermal Field (SSGF). Between these wells, a shale layer has been correlated which appears to divide the reservoir into an upper and lower portion. Other thick sand and shale sequences may provide additional stratification. This report describes work in progress on a well testing program designed to determine the horizontal and vertical transmissivity and storage parameters between wells in the vicinity of the GLEF. These tests are being conducted with the cooperation and support of Magma Power Company and San Diego Gas and Electric Company. 3 figs., 4 refs.

Hot water geothermal fields discharge steam-water mixtures, which have proved difficult to measure compared with the dry steam from fields like The Geysers and Lardarello. Hot water geothermal fields discharge steam-water mixtures, which have proved difficult to measure compared with the dry steam from fields like The Geysers and Lardarello. With the development of the lip pressure method, however (James 1962), an accurate method was derived which could measure the flow when a geothermal well discharges to the atmosphere at sonic velocity. Fortunately most discharges from wells do in fact attain such velocities, and as long as the enthalpy of the mixture is known, the flow can be determined. Where the enthalpy is unknown some other measurement has also to be made in order to solve the two factors of flow and enthalpy. By discharging the whole mixture into a silencer, the water portion can be estimated by means of a weir, and this provides the second measurement (described in James 1966) required to solve both unknowns. With the hoped-for commercial success of the total energy turbine in the near future, it will be necessary to have a means of measuring the steam-water flow into the machine. As long as …

Smith et al (1975) have proposed the creation of man-made geothermal energy reservoirs by drilling into relatively impermeable rock to a depth where the temperature is high enough to be useful; creating a reservoir by hydraulic fracturing; and then completing the circulation loop by drilling a second hole to intersect the hydraulically fractured region. The initiation of hydraulically created fluid reservoirs in highly impermeable hot dry rock must by definition take place in a wellbore. The nature of these initiation sites will provide the initial resistance to flow into the reservoir and therefore will strongly influence the rate of energy withdrawal. The nature of the interception site in a second wellbore which has been directed to intersect the reservoir will have a similar effect. The program to create and study such artificial geothermal reservoirs in hot dry rock is being pursued by the Los Alamos Scientific Laboratory and has been presented to these workshops by Murphy (1975) and Murphy et al (1976). In parallel with the drilling of the two boreholes rather complete suites of wellbore geophysical logs were run followed by further diagnostic logging both during and after fracturing operations. This paper discusses some aspects of what has been …

A multiphase consolidation theory is presented which considers a three-dimensional deformation field coupled with a three-dimensional hydrologic flow field. The governing system of equations describes the components of displacement, the fluid pressures and the saturations. The system of equations governing saturated-unsaturated consolidation is obtained as a subset of the above equations. A mixed stress-displacement formulation of the governing equations is introduced, and it facilitates handling of load type boundary conditions while solutions in terms of displacements are still possible. Finite element Galerkin theory is used for spatial approximations, and a weighted implicit finite difference time-stepping scheme is employed to approximate the time derivative terms. Due to the nonlinear nature of the problem, an iterative solution scheme is necessary within each time step. The model predicts the commonly ignored horizontal displacements in a variably saturated system undergoing simultaneous desaturation and deformation, while using a completely interconnected coupling of the stress and pressure fields within the medium. The model is applied to obtain vertical and horizontal displacements, pressure (head) and saturation values due to pumpage in a phreatic aquifer. 1 tab., 10 figs., 13 refs.

The engineering necessity of achieving maximum cooling of the borehole during drilling and logging operations on geothermal wells prohibits the determination of equilibrium temperature in the sub-surface before virtual rebound from the drilling disturbance some months after operations cease. Clearly, substantial economic benefits would accrue, in many cases, if a reasonable prediction of equilibrium temperature can be made while the rig is still over the borehole. The purpose of this brief report is to provide an abbreviated explanation of the physical principles of temperature rebound and provide a convenient plotting method similar to the Horner plot in order to standardize temperature prediction in Geothermal Operations. It has the further purpose of outlining methods to determine an approximate thermal conductivity value for reservoir rocks and rebound times after drilling from the nature of the rebound curve. 2 refs., 2 figs.

Flow tests and pressure measurements were made on a group of five wells in the Momotombo geothermal reservoir, Nicaragua. The purpose of these tests was to evaluate the hot water reservoir, to determine well interference effects, to determine reservoir boundary conditions and to obtain mass flow rates and enthalpy. Static bottom hoe pressures were measured on three wells and bottom hole flowing pressures and shut-in buildup pressures were measured on one of the wells. A Hewlett-Packard quartz crystal pressure gauge was used in connection with a Sperry Sun expandable chamber hung on steel capillary tubing to measure downhole pressure. Flow tests were made on all five wells. Four wells were flowed through a horizontal discharge pipe. One well was flowed through a vertical discharge pipe. 2 refs., 7 figs.

White, Muffler, and Truesdell (1971) and Truesdell and White (1973) developed a conceptual model of transport in vapor-dominated geothermal zones. The main theme of the model is that coexisting liquid and vapor phases form a counterflowing convection system similar to that observed in a heat pipe (Dunn and Reay, 1976). It is hypothesized that water evaporates from a deep water table, passes upward through the formation, and condenses at an impermeable cap rock, effectively transferring the latent heat of boiling through the formation. The liquid water then percolates downward, completing the cycle. The physics involved in the flow system is illustrated in an analysis of an idealized one-dimensional, homogeneous, 2 km deep vapor-dominated zone which is bounded below by a water table which has a temperature of 236°C. Flow of water and steam in the system is assumed to be described by Darcy’s law for unsaturated porous materials. The liquid water potential, defined as the Gibbs free energy per unit volume of water, is used in place of the liquid pressure in the equation for water because flow in a highly unsaturated medium is to be considered. Comparison of figures 2 and 4 illustrates that the liquid saturation in a …

During reinjection of cooled geothermal fluid into a reservoir, chemical precipitation and other processes may occur changing the permeability of the aquifer. In general, the permeability becomes a function both of time and space. This will, of course, affect the injection well. Some attempts have been made to analytically predict the pressure response. The present paper describes our calculations which yield analytic expressions, in terms of a single integral, for a wide class of physically reasonable permeability functions. Results are presented for a few typical examples. 6 figs.

To assess the importance of the confidence level of geothermal resources to those involved with the decisions on utilization, it was felt that a panel discussion to review the factors which affect the confidence level would be of general interest. With that objective, the panel members listed above were convened to discuss the problems of confidence level of the various sectors of the geothermal community. To allow for freedom of expression of the panel members, formal prepared presentations were not required. Instead three rapporteurs also representing diverse sectors of the community, industry, non-profit institutions, and government agencies, were requested to prepare summary overviews of the panelists remarks. The rapporteur reports follow.

Since the last conference, a fourth well has been drilled to an intermediate depth and tested as a production well, with plans to use this well in the long term for injection of fluids into the strata above the production strata. The third, triple legged well has been fully pump tested, and the recovery of the second well from an injection well back to production status has revealed very interesting data on the reservoir conditions around that well. Both interference testing and geochemistry analysis shows that the third well is producing from a different aquifer than that supplying the No. 2 well. There is an effective barrier, yet unidentified as to structure, making pressure communication between these aquifers quite negligible. These results have led to significantly different models for the aquifer system than those previously believed to apply. 3 figs., 1 tab., 3 refs.

In this paper we briefly describe the lithology, temperature, and pressure of the Heber Geothermal Reservoir. This we base on the extensive data gathered in the past few years through well drilling and testing. We then describe our three-dimensional, heterogeneous, single phase water flow simulator, including the equations solved, and the assumptions made. We present several applications of the numerical simulator, in predicting the reservoir behavior with time. Conclusions based on an analysis of simulator results are finally presented. 2 refs., 5 figs.

The producing characteristics of vapor-dominated geothermal steam reservoirs bear some strong resemblances to those observed in hydrocarbon natural gas reservoirs. Consequently, many geothermal steam well tests are commonly analyzed using flow theory developed for the isothermal flow of hydrocarbon natural gases. Such analysis is most often made using the idealization of perfect gas fluid flow behavior in the reservoir. This study investigated the real gas flow characteristics of geothermal steam over the ranges of pressure, temperature, and noncondensable gas content commonly found in vapor dominated geothermal systems. Details of this study are available elsewhere (Mannon, 1977). These results will allow the reservoir engineer to more accurately analyze transient flow of superheated geothermal steams. Geothermal steam wells have traditionally been analyzed using the ideal gas flow model, described by Eq. 1, without quantitative justification. The results of this study will allow for quantitative justification of the ideal gas flow assumption, where possible. Alternatively, they will facilitate use of the more correct pseudo-pressure function when analyzing geothermal steam wells. 5 refs., 2 tabs., 2 figs.

The Reservoir Engineering Management Program being conducted at Lawrence Berkeley Laboratory includes two major tasks: 1) the continuation of support to geothermal reservoir engineering related work, started under the NSF-RANN program and transferred to ERDA at the time of its formation; 2) the development and subsequent implementation of a broad plan for support of research in topics related to the exploitation of geothermal reservoirs. This plan is now known as the GREMP plan. Both the NSF-RANN legacies and GREMP are in direct support of the DOE/DGE mission in general and the goals of the Resource and Technology/Resource Exploitation and Assessment Branch in particular. These goals are to determine the magnitude and distribution of geothermal resources and reduce risk in their exploitation through improved understanding of generically different reservoir types. These goals are to be accomplished by: 1) the creation of a large data base about geothermal reservoirs, 2) improved tools and methods for gathering data on geothermal reservoirs, and 3) modeling of reservoirs and utilization options. The NSF legacies are more research and training oriented, and the GREMP is geared primarily to the practical development of the geothermal reservoirs. 2 tabs., 3 figs.

The East Mesa KGRA (Known Geothermal Resource Area) is located in the Imperial Valley of Southern California close to the Mexican border. Republic Geothermal, Inc. has leased lands in the northern part of the geothermal anomaly and has so far drilled six wells, ranging in depth from 7,400 to 9,100 feet. Current plans of Republic include construction of a 50 MW power plant based on the resource. Crucial to the success of this venture is a proper understanding of the physical properties of the geothermal reservoir tapped by the wells. Towards the south, the geothermal anomaly is being explored and assessed by the U.S. Bureau of Reclamation (5 wells) and the Magma Power Co. (3 wells). In order to achieve a proper understanding of the resource at East Mesa, Lawrence Berkeley Laboratory collaborated with Republic in conducting a series of three well tests. These included production, injection and interference tests with durations varying from a few days to several weeks and yielded valuable information on reservoir parameters as well as geometry. The purpose of this presentation is to summarize the important findings from the tests. In particular, attention will be restricted to the production-interference tests. The results of injection tests …

The emphasis of the smaller scale laboratory of the Stanford Geothermal Program is on improving the understanding of the physics of flow through porous materials in a geothermal environment. Three major investigations are in progress: (1) examination of the phenomenon of vapor pressure lowering in porous media, (2) determination of the temperature dependence of absolute and relative permeabilities of steam and water in sandstones under high confining pressures, and (3) observation of steady and unsteady, single- and two-phase flows of water or brine through permeable cores. In addition, development continues on the dielectric constant liquid content detector—a device which would prove extremely useful in these and subsequent experiments. 10 refs., 4 figs.

The author distinguishes between geothermal resource base, accessible geothermal resource base, geothermal resource, and geothermal reserve. Conditions for periodically updating the assessment of geothermal energy resources include: increased data from expanded exploration and drilling; development of improved and new technologies for exploration, evaluation, extraction, and use; rapid evolution of geothermal knowledge; and the increased role of geothermal energy in response to changing economic, social, political, and environmental conditions, particularly an increasing awareness of the limits to petroleum and natural gas resources. Accordingly, the U. S. Geological Survey (USGS) plans by the end of 1978 to update its 1975 assessment of the United States’ geothermal resource, with increased emphasis on several items. The USGS’s joint evaluations of geothermal resource-assessment techniques in the last year with the National Electric Agency of Italy (ENEL) under U. S. Energy Research and Development Agency sponsorship identified a number of problems, one of which was how to formulate geothermal recovery factors for systems producing by intergranular vaporization and by intergranular flow. The first formulation is fairly rigorous; the author solicits the reservoir engineering community’s help in improving the estimate of the second. 3 figs., 11 refs.

The report identifies barriers to shortening nuclear power plant construction schedules and recommends research efforts which should minimize or eliminate the identified barriers. The identified barriers include (1) Design and Construction Interfacing Problems; (2) Problems Relating to the Selection and Use of Permanent Materials and Construction Methods; (3) Construction Coordination and Communication Problems; and (4) Problems Associated with Manpower Availability and Productivity.