The performance of binary geothermal power plants can be improved through the proper choice of a working fluid, and optimization of component designs and operating conditions. This paper reviews the investigations at the Idaho National Engineering Laboratory (INEL) which are examining binary cycle performance improvements: for moderate temperature (350 to 400 F) resources with emphasis on how the improvements may be integrated into design of binary cycles. These investigations are examining performance improvements resulting from the supercritical vaporization of mixed hydrocarbon working fluids and achieving countercurrent integral condensation with these fluids, as well as the modification of the turbine inlet state points to achieve supersaturated turbine vapor expansions. For resources where the brine outlet temperature is restricted, the use of turbine exhaust recuperators is examined. The baseline plant used to determine improvements in plant performance (characterized by the increase in the net brine effectiveness, watt-hours per pound of brine) in these studies operates at conditions similar to the 45 MW Heber binary plant. Through the selection of the optimum working fluids and operating conditions, achieving countercurrent integral condensation, and allowing supersaturated vapor expansions in the turbine, the performance of the binary cycle (the net brine effectiveness) can be improved by …

My assignment is to give feedback on the Reservoir Technology Task portion of the DOE-sponsored work we've been hearing about. Briefly, you've done well in adapting to an increasingly tough budgetary and political environment. More specifically, I'd like to highlight some of the encouraging developments in the context of overall research strategy. Ted Mock on Tuesday and Ken Nemzer at yesterday's luncheon made several useful observations and I'd like to refer to just two in relation to Reservoir Technology. Ted observed that product development can proceed along two paths. We might call these the Big Bang or the Evolutionary lines. He correctly pointed out the difficulty American industry has had with commercializing incremental (Evolutionary) product improvements. In this context Reservoir Technology development is more like manufacturing engineering because we aren't developing new products, for the most part. We are simply working to produce electricity or process heat cheaper. The DOE has listened to industry on this point and their statement of objectives sounds excellent. Let me quote one example from Page 10 of the December 20, 1988 report. For ''Reservoir Evaluation'' we read ''Decrease uncertainties...20% by 1993''. I confess that I don't know what the uncertainty is in 1989, but …

I am pleased with the research support provided by DOE, as it has resulted in products that are in use today, which reduce our cost of producing energy. Since we must compete in the energy market against other energy sources, such as coal, we needed to be cost competitive with these other sources. Research on these competitive sources will lower their costs in the future. We need to progress in our research to remain competitive. One question is whether the current DOE program will continue to provide the level of research advances we have benefited from in the past, even though the level of funding is significantly less. I believe that the funding level is too low if we want to maintain the same technology development pace. Ignoring the funding level, the remaining question is whether the highest priority projects (by industry's definition) are the ones being worked on by DOE. There is a mix of medium-term and long-term projects in the DOE Drilling and Completion program (about 30% short/70% long). I believe that industrial research would operate with these percentages reversed, and the preference for more short-term research is manifested by questioning the appropriateness of HDR & Magma research. …

The stated goal of Geothermal Technology Division (GTD's) research program is to provide technical solutions required to establish all forms of this resource as long-term competitive energy alternatives. Especially at a time when the research budget is relatively small and competitive energy alternatives are relatively cheap, the emphasis on achieving tangible economic benefits through research is appropriate. In the case of a new technology such as tapping magma energy, it is too early to fine-tune the economics, but the research is well-justified by the magnitude of the potential resource. For projects aimed at incremental improvements in processes that are already commercial, economic potential is more easily defined. Fluid production research generally falls in the latter category. In keeping with the foregoing, it would be desirable for the research program participants to place greater emphasis on the potential applications and economic impact of their respective projects. Specifically, with regard to research projects aimed at improving the economics of existing commercial operations, the following points should be addressed: (1) in what resources, or types of resources, would the research results be applicable; (2) what are the best commercially available materials or techniques available, and how will the results of research improve operations …

The Magma Energy Program of the Geothermal Technology Division is scheduled to begin drilling a deep (6 km) exploration well in Long Valley Caldera, California in 1989. The drilling site is near the center of the caldera which is associated with numerous shallow (5-7 km) geophysical anomalies. This deep well will present an unparalleled opportunity to test and validate geophysical techniques for locating magma as well as a test of the theory that magma is still present at drillable depths within the central portion of the caldera. If, indeed, drilling indicates magma, the geothermal community will then be afforded the unique possibility of examining the coupling between magmatic and hydrothermal regimes in a major volcanic system. Goals of planned seismic experiments that involve the well include the investigation of local crustal structure down to depths of 10 km as well as the determination of mechanisms for local seismicity and deformation. Borehole electrical and electromagnetic surveys will increase the volume and depth of rock investigated by the well through consideration of the conductive structure of the hydrothermal and underlying regimes. Currently active processes involving magma injection will be studied through observation of changes in pore pressure and strain. Measurements of in …

As a response to the America's need for alternate energy sources, the US Department of Energy has a Geothermal Program. Within this program is a category to study Geopressured Energy. Today many activities are taking place under the Geopressured Program. These activities for the most part fall under one of the following categories: Well Operations, Geoscience and Engineering Support and Energy Conversion. To date this program has had many successes. However, there is still more information needed concerning the Geopressured Resource. it is thought that continued research will give the developer a better understanding of the Geopressured resource and in turn increase the likelihood of it's development.

Extensive laboratory studies have indicated that the application of biochemical processes in the development of biotechnology suitable for conversion of geothermal wastes from hazardous to non-hazardous materials is technically and economically feasible. These studies have also shown that such biotechnology may require bioreactors capable of handling different amounts and types of residual sludges. Particular attention has to be paid to the duration of treatment, efficiency of cycling, and maintenance of biomass. Laboratory studies addressing these parameters are described.

This audience is well aware that the major goal of all geothermal R&D is the successful application of advanced technology in the marketplace. In support of that goal, the Geothermal Technology Division has forged a close link between its research objectives and potentially competitive market applications. Our technical objectives are all expressed in quantified reductions in the cost of geothermal power; these cost reductions are the force that will drive the geothermal industry for the foreseeable future. I agree with the recent statement of Stephen Fye of Unocal that without a legislated incentive for geothermal or disincentive for competing fuels-such as mandated carbon dioxide reductions--any premium the public is willing to pay for the use of this premium fuel will be too small to greatly impact geothermal economics. His conclusion is that the geothermal industry must be fully competitive in the marketplace at current prices. His further conclusion--with which I fully concur--is that the avenue to competitiveness is through research, by both industry and government.

This paper is a summary of the proposed drilling plan for the first phase (to 2500 feet depth) of the Magma Energy Exploratory Well. The drilling program comprises four phases, spaced approximately one year apart, which culminate in a large-diameter well to a total depth near 20,000 feet. Included here are descriptions of the well design, predictions of potential drilling problems, a list of restrictions imposed by regulatory agencies, an outline of Sandia's management structure, and an explanation of how the magma energy technology will benefit from this drilling.

The Geothermal direct use industry potential, growth trends, needs, and how they are being met, are addressed. The high potential for industry growth, coupled with a rapidly expanding use of geothermal energy for direct use, and concerns over the greenhouse effect is the setting in which a new engineering and design guidebook is being issued to support the growth of the geothermal direct use industry. Recent investigations about the current status of the industry and the identification of technical needs of current operating district heating systems provide the basis upon which this paper and the guidebook is presented. The guidebook, prepared under the auspices of the U.S. Department of Energy, attempts to impart a comprehensive understanding of information important to the development of geothermal direct use projects. The text is aimed toward the engineer or technical person responsible for project design and development. The practical and technical nature of the guidebook answers questions most commonly asked in a wide range of topics including geology, exploration, well drilling, reservoir engineering, mechanical engineering, cost analysis, regulations, and environmental aspects.

The geothermal industry has shown significant interest in case histories that document field production histories and demonstrate the techniques which work best in the characterization and evaluation of geothermal systems. In response to this interest, LBL has devoted a significant part of its geothermal program to the compilation and analysis of data from US and foreign fields (e.g., East Mesa, The Geysers, Susanville, and Long Valley in California; Klamath Fall in Oregon; Valles Caldera, New Mexico; Cerro Prieto and Los Azufres in Mexico; Krafla and Nesjavellir in Iceland; Larderello in Italy; Olkaria in Kenya). In each of these case studies we have been able to test and validate in the field, or against field data, the methodology and instrumentation developed under the Reservoir Technology Task of the DOE Geothermal Program, and to add to the understanding of the characteristics and processes occurring in geothermal reservoirs. Case study results of the producing Cerro Prieto and Olkaria geothermal fields are discussed in this paper. These examples were chosen because they illustrate the value of conceptual and numerical models to predict changes in reservoir conditions, reservoir processes, and well performance that accompany field exploitation, as well as to reduce the costs associated with …

The western power surplus is finite and electric load growth is persistent. Concerns about availability and environmental effects will overshadow life-cycle cost in selection of tomorrow's sources. Geothermal's growth and achievements qualify it as a preferred resource for the 1990s and beyond but its merits remain largely unknown in political and financial circles. Near-term needs include power sales contracts after 1990, improved comfort for banks and utilities with reservoir assessment techniques and mitigation of financial risks at pilot plants on new fields. Institutional, not technical, issues will dominate geothermal energy's growth, performance, image and utility relationships in the 1990s.

The application of passive seismic studies in geothermal regions have undergone significant changes in the last 15 years. The primary application is now in the monitoring of subsurface processes, rather than exploration. A joint Geothermal Technology Organization (GTO) industry/DOE, monitoring project involving GEO, Unocal Geothermal, and LBL, was carried out at The Geysers geothermal field in northern California using a special high frequency monitoring system. This several-month-long experiment monitored the discrete and continuous seismic signals before, during, and after a fluid stimulation of a marginal production well. Almost 350,000 liters of water were pumped into the well over a four-hour, and a three-hour time period for two consecutive days in June of 1988. No significant changes in the background seismicity or the seismic noise were detected during the monitoring period. Analysis of the background seismicity did indicate that the earthquakes at The Geysers contain frequencies higher than 50 Hz. and possibly as high as 100 Hz.

Discrete fracture and continuum models are being developed to simulate Hot Dry Rock (HDR) geothermal reservoirs. The discrete fracture model is a two-dimensional steady state simulator of fluid flow and tracer transport in a fracture network which is generated from assumed statistical properties of the fractures. The model's strength lies in its ability to compute the steady state pressure drop and tracer response in a realistic network of interconnected fractures. The continuum approach models fracture behavior by treating permeability and porosity as functions of temperature and effective stress. With this model it is practical to model transient behavior as well as the coupled processes of fluid flow, heat transfer, and stress effects in a three-dimensional system. The model capabilities being developed will also have applications in conventional geothermal systems undergoing reinjection and in fractured geothermal reservoirs in general.

The Hot Dry Rock (HDR) geothermal energy program is a renewable energy program that can contribute significantly to the nation's balanced and diversified energy mix. Having extracted energy from the first Fenton Hill HDR reservoir for about 400 days, and from the second reservoir for 30 days in a preliminary test, Los Alamos is focusing on the Long Term Flow Test and reservoir studies. Current budget limitations have slowed preparations thus delaying the start date of that test. The test is planned to gather data for more definitive reservoir modeling with energy availability or reservoir lifetime of primary interest. Other salient information will address geochemistry and tracer studies, microseismic response, water requirements and flow impedance which relates directly to pumping power requirements. During this year of ''preparation'' we have made progress in modeling studies, in chemically reactive tracer techniques, in improvements in acoustic or microseismic event analysis.

This letter report describes the technical activities of the waste element solubility study during Fiscal Year (FY88, October 1, 1987 to September 30, 1988). This experimental waste element solubility study provides experimentally determined limits on radionuclide concentrations in groundwater from Yucca Mountain. Furthermore, the results of this study are essential for verifying the validity of radionuclide transport calculations, and for providing the maximum concentrations for the radionuclide sorption tests. Solubility is the source term for radionuclide transport calculations. The solubility in this study is controlled by fewer variables than are used in the multiparameter transport model. Therefore, modeling must be capable of predicting the results of this waste element solubility study. Agreement between the experimental result and the modeling predictions will validate the geochemical module of the transport model. 3 refs., 8 figs.

Up to 500,000 Quads of thermal energy are believed to be contained in crustal magma bodies within the U.S. at temperatures in excess of 600 C and at depths less than 10 km. Scientific feasibility of utilizing this energy resource was concluded after a seven-year study that culminated in successful energy extraction experiments in molten rock at Kilauea Iki lava lake. The current DOE program is developing technology to experimentally extract energy from a silicic magma body so that engineering feasibility of the magma energy concept can be evaluated. At this point, significant progress has been achieved in three areas: Geophysics and site selection. Energy Extraction Processes, and Geochemistry/Materials. Future activities will be focused by drilling and evaluating a deep exploratory well in Long Valley caldera where active magma is expected.

In order to assure the continued development of geothermal resources, many advances in materials technology are required so that high costs resulting from the severe environments encountered during drilling, well completion and energy extraction can be reduced. These needs will become more acute as higher temperature and chemically aggressive fluids are encountered. High priority needs are for lost circulation control and lightweight well completion materials, and tools such as drill pipe protectors, rotating head seals, blow-out preventers, and downhole drill motors. The lack of suitable hydrolytically stable chemical systems that can bond previously developed elastomers to metal reinforcement is a critical but as yet unaddressed impediment to the development of these tools. In addition, the availability of low cost corrosion and scale-resistant tubular lining materials would greatly enhance transport and energy extraction processes utilizing hypersaline brines. Work to address these materials needs is underway at Brookhaven National Laboratory (BNL), and recent accomplishments are summarized in the paper.

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The DOE Hard Rock Penetration program is developing technology to reduce the costs of drilling geothermal wells. Current projects include: R & D in lost circulation control, high temperature instrumentation, underground imaging with a borehole radar insulated drill pipe development for high temperature formations, and new technology for data transmission through drill pipe that can potentially greatly improve data rates for measurement while drilling systems. In addition to this work, projects of the Geothermal Drilling Organization are managed. During 1988, GDO projects include developments in five areas: high temperature acoustic televiewer, pneumatic turbine, urethane foam for lost circulation control, geothermal drill pipe protectors, an improved rotary head seals.

This study discusses the application of algorithms developed in Operations Research to the optimization of brine reinjection in geothermal fields. The injection optimization problem is broken into two sub-problems: (1) choosing a configuration of injectors from an existing set of wells, and (2) allocating a total specified injection rate among chosen injectors. The allocation problem is solved first. The reservoir is idealized as a network of channels or arcs directly connecting each pair of wells in the field. Each arc in the network is considered to have some potential for thermal breakthrough. This potential is quantified by an arc-specific breakthrough index, b{sub ij}, based on user-specified parameters from tracer tests, field geometry, and operating considerations. The sum of b{sub ij}-values for all arcs is defined as the fieldwide breakthrough index, B. Injection is optimized by choosing injection wells and rates so as to minimize B subject to constraints on the number of injectors and the total amount of fluid to be produced and reinjected. The use of the various methods is demonstrated with reference both to hypothetical data and an actual data set from the Wairakei Geothermal Field in New Zealand.

As a response to America's need for Alternate Energy sources, the U.S. Department of Energy has a Geothermal Program. Within this program is a Hydrothermal category. Currently, a wide range of tasks are being addressed as part of the Hydrothermal Program. The tasks include Industrialization, Reservoir Technology, Hard Rock Penetration and Conversion Technology. It is thought that successes already made in this program combined with upcoming successes will increase the likelihood of geothermal energy becoming a contributor to our nations future energy needs.

Logging research at The University of Texas has been carried out in several areas. We have studied how rock resistivity varies with water saturation when other variables, such as rock wettability, stress, saturation history, and shale content are varied. Both experimental and theoretical work have been done. Rock wettability (oil or water wet) has by far the largest effect. Shale content and saturation history are also important. Rock stress is the least important, at least in the Berea sandstones and glass bed packs we have studied. We have published several papers and theses which describe this work in detail. We have also studied the effect of certain trace elements (boron, mainly) on the neutron log. Boron has a very high thermal neutron capture cross Section. Analyses of a number of Frio formation cores from the Texas Gulf Coast area show that boron occurs frequently in these rocks in amounts (up to 100 ppm or more) that would seriously affect several procedures in neutron log interpretation. It could, for example, reduce or even eliminate the neutron log--density log porosity reversal that is commonly used as a gas indicator. A recent paper reports details of our work in the Frio. We are …

This project will demonstrate the Hybrid Cycle Concept for electricity generation using geopressured-geothermal resources. The test is scheduled to be a minimum of one year, which may be extended. The majority of the equipment came from the DOE facility at East Mesa, CA. The hybrid cycle has been designed for 10,800 BPD brine and 220,000 SCFD of gas. The power output will be about one megawatt, which will be sold to Houston Lighting and Power Company. An important research objective is to determine the size and ultimate production capability of the geopressured-geothermal reservoir. The long-term deliverability of these type reservoirs is a significant factor in determining the ultimate economic capability of these systems.