Geopressured reservoirs contain three types of energy: thermal, hydraulic, and methane gas. The thermal energy generally is a function of depth of burial. It can be converted to electricity using the binary or flash power plant cycle, the flash technology being commercial only if the fluid temperature exceeds about 340 F. The hydraulic energy can be converted to electrical power using a hydraulic turbine. The dissolved gas can be separated and either used to produce electricity using a gas turbine or sold commercially. These reservoirs occur in many states in the USA, including California. An overburden pressure is caused by the combined weight of the formation rock and the fluids (water/gas/oil) present in the pore spaces overlying the formation of interest. The overburden pressure, in general, increases relatively uniformly with depth, whereas the hydrostatic gradient is mainly a function of two variables: the dissolved solids concentration and the temperature gradient. The hydrostatic pressure gradient for fresh water is 0.433 psi/ft. Geopressured reservoirs are overpressured; that is, the fluid pressure in the reservoir exceeds the pressure corresponding to the local hydrostatic pressure gradient. (Fig. 3) Confining bed or cap rock is necessary in order for a formation to be geopressured. Otherwise, …

The Heat Cycle Research project is developing the technology base that will permit a much greater utilization of the moderate-temperature, liquid-dominated geothermal resources, particularly for the generation of electrical power. The emphasis in the project has been the improvement of the performance of binary power cycles. The investigations have been examining concepts projected to improve the brine utilization by 20% relative to a ''Heber-type'' binary plant; these investigations are nearing completion. preparations are currently underway in the project to conduct field investigations of the condensation behavior of supersaturated turbine expansions. These investigations will evaluate whether the projected additional 8% to 10% improvement in brine utilization can be realized by allowing these expansions. Future program efforts will focus on the problems associated with heat rejection and on the transfer of the technology being developed to industry.

As part of The Geysers research activities of DOE's Geothermal Reservoir Technology Program, LBL, in close cooperation with industry, is performing fundamental and applied studies of vapor-dominated geothermal systems. These studies include the development of new methods for evaluating cold water injection, monitoring of the seismic activity in The Geysers associated with injection and production, interpretation of pressure and geochemical changes measured during well tests and long-term production and injection operations, and improvement of existing models of the geothermal system. A review is given of the latest results of DOE-sponsored LBL reservoir engineering and seismic studies relevant to The Geysers.

Preliminary flow and pressure testing of the Phase II Hot Dry Rock (HDR) reservoir at Fenton Hill, New Mexico, as part of the preparations for the initial 90-day segment of the Long-Term Flow Test, has revealed several significant features concerning the hydraulic behavior of this reservoir as a function of injection and production pressure levels. Of most significance to the future operation of HDR power plants is the influence of elevated production backpressure on the effective reservoir flow impedance (i.e., the difference between injection and production pressures, divided by the production flow rate). It has been found that the effective flow impedance at high backpressure is significantly lower than the corresponding impedance at low backpressure. At an injection pressure of 3700 psi and a back-pressure of 2210 psi, the effective flow impedance for the present reservoir is 20 psi/gpm--less than 40% of the effective flow impedance for similar injection conditions, but at low backpressure (about 170 psi). Recently, a 10-day reservoir flow test was conducted at a somewhat lower backpressure of 1500 psi, and at a slightly higher injection pressure of 3750 psi. At these new conditions, there was an increase in the effective reservoir flow impedance to 23.6 psi/gpm, …

I'm pleased to be here as your keynote speaker from the utility industry. Today is fitting to discuss the role of an alternative/renewable energy resource such as geothermal. Three years ago today, the Exxon Valdez oil tanker spilled 11 million gallons of oil into Prince William Sound, Alaska. This ecological catastrophe was another of those periodic jolts that underscores the importance of lessening our nation's dependence on oil and increasing the use of cost-effective, environmentally benign alternative/renewable energy sources. Alternative/renewables have come a long way since the first oil crisis in 1973. Today, they provide 9 percent of electric power used in the United States. That's nearly double the figure of just two years ago. And since 1985, one-third of a new capacity has come from geothermal, solar, wind and biomass facilities. Nevertheless, geothermal supplies only about three-tenths of a percent of the country's electric power, or roughly 2,800 megawatts (MW). And most of that is in California. In fact, geothermal is California's second-largest source of renewable energy, supplying more than 5 percent of the power generated in the state. Today, I'd like to discuss the outlook for the geothermal industry, framing it within Southern California Edison's experience with geothermal …

The results from the tests of the first large area (4 [times] 4 cm[sup 2]) planar silicon drift detector prototype in a pion beam are reported. The measured position resolution in the drift direction is ([sigma]=40 [plus minus] 10)[mu]m.

The results from the tests of the first large area (4 {times} 4 cm{sup 2}) planar silicon drift detector prototype in a pion beam are reported. The measured position resolution in the drift direction is ({sigma}=40 {plus_minus} 10){mu}m.

A two-pass surface extraction algorithm for adaptive finite element meshes is presented in the context of a visualization study for a particle impact and a turbine containment problem. The direct use of finite element data structures for the computation of external surfaces, surface normals, and derived physical quantities is discussed. An overview of the in-betweening algorithm which compensates for rigid body dynamics is presented with a brief discussion of a {open_quotes}direct-to-videodisk{close_quotes} animation strategy.

Acoustic telemetry has been a dream of the drilling industry for the past 50 years. It offers the promise of data rates which are one-hundred times greater than existing technology. Such a system would open the door to true logging-while-drilling technology and bring enormous profits to its developers. The oil and gas industry has led in most of the attempts to develop this type of telemetry system; however, very substantial efforts have also been made through government sponsored work in the geothermal industry. None of these previous attempts have lead to a commercial telemetry system. Conceptually, the problem looks easy. The basic idea is to produce an encoded sound wave at the bottom of the well, let it propagate up the steel drillpipe, and extract the data from the signal at the surface. Unfortunately, substantial difficulties arise. The first difficult problem is to produce the sound wave. Since the most promising transmission wavelengths are about 20 feet, normal transducer efficiencies are quite low. Compounding this problem is the structural complexity of the bottomhole assembly and drillstring. For example, the acoustic impedance of the drillstring changes every 30 feet and produces an unusual scattering pattern in the acoustic transmission. This scattering …

The UCSD brine chemistry program is providing highly accurate models of the behavior of high temperature brines to be used by the geothermal community to optimize production, interpret formation behavior and assist in performance assessment. Models are now available as user-oriented programs packaged for both main frame and personal computers (IBM and Macintosh). A manual describing the models and their application to various geothermal problems has been developed and made available to potential users. Tutorial sessions have been held and future sessions are planned. Present models can be used to predict the behavior of many important geothermal processes. For example, the tendency for production fluids to form carbonate, silica and sulfate scales can be predicted as a function of brine composition, temperature and CO{sub 2} partial pressure. The breakout pressure (onset of two phase flow) can be calculated as a function of temperature and brine composition. Preliminary models are available for characterizing H{sub 2}S gas/liquid distributions and the acid-base properties of the H{sub S}S-H{sub 2}O system as a function of brine composition, temperature and pressure. For the past year, a substantial part of this research has focused on the prediction of the properties of gases in the CO{sub 2}-CH{sub 4}-H{sub …

The long term flow test (LTFT) of the worlds largest, deepest, and hottest hot dry rock (HDR) reservoir currently underway at Fenton Hill, NM, is expected to demonstrate that thermal energy can be mined from hot rock within the earth on a sustainable basis with minimal water consumption. This test will simulate the operations of a commercial facility in some ways, but it will not show that energy from HDR can be produced at a variety of locations with different geological settings. Since the Fenton Hill system was designed as a research facility rather than strictly for production purposes, it will also not demonstrate economic viability, although it may well give indications of system modifications needed for economic HDR operations. A second production site must be constructed, ideally under the direction of the private geothermal community, to begin the process of proving that the vast HDR resources can be accessed on a worldwide scale. This facility should be designed and engineered to produce and market energy at competitive prices. At the same time, a wide variety of techniques to advance the state-of-the-art of HDR technology must be pursued to develop this infant technology rapidly to its maximum potential. A number …

The Hard Rock Penetration program is developing technology to reduce the costs of drilling and completing geothermal wells. Current projects include: lost circulation control, rock penetration mechanics, instrumentation, and industry/DOE cost shared projects of the Geothermal Drilling Organization. Last year, a number of accomplishments were achieved in each of these areas. A new flow meter being developed to accurately measure drilling fluid outflow was tested extensively during Long Valley drilling. Results show that this meter is rugged, reliable, and can provide useful measurements of small differences in fluid inflow and outflow rates. By providing early indications of fluid gain or loss, improved control of blow-out and lost circulation problems during geothermal drilling can be expected. In the area of downhole tools for lost circulation control, the concept of a downhole injector for injecting a two-component, fast-setting cementitious mud was developed. DOE filed a patent application for this concept during FY 91. The design criteria for a high-temperature potassium, uranium, thorium logging tool featuring a downhole data storage computer were established, and a request for proposals was submitted to tool development companies. The fundamental theory of acoustic telemetry in drill strings was significantly advanced through field experimentation and analysis. A new …

America's increasing dependence on foreign energy sources, and the national environmental initiatives, based on the increasing awareness of the need for protection of the environment, have led to the development of the Department of Energy's (DOE) domestic US alternative energy programs. One of these programs is the current US Gulf Coast Geopressured-Geothermal Program, conducted at three sites in Louisiana and Texas. Excellent results have been obtained in reaching the objectives for this production operation and energy conversion project, which are: (1) to determine the size of geopressured-geothermal reservoirs and the drive mechanisms by long-term, high volume, flow testing; (2) prove long-term injectability of large volumes of spent brine; (3) develop modified scale inhibitor treatment procedures; (4) develop methods for reduction of erosion/corrosion; (5) develop technology for automated operation of geopressured-geothermal production system; and (6) develop technology to produce power economically from the geopressured-geothermal resources. The long-term flow test at the Gladys McCall site has shown the producing reservoir is many times it original, projected size. Flow tests are being conducted at the Pleasant Bayou site in Texas. Another reservoir, at the Hulin site in Louisiana, remains for initiation of testing, at a time to be determined. Gas sales and electrical …

Phase II of the Long Valley Exploratory Well was completed to a depth of 7588 feet in November 1991. The drilling comprised two sub-phases: (1) drilling 17-1/2 inch hole from the Phase I casing shoe at 2558 feet to a depth of 7130 feet, plugging back to 6826 feet, and setting 13-3/8 inch casing at 6825 feet, all during August-September 1991; and (2) returning in November to drill a 3.85-inch core hole deviated out of the previous wellbore at 6808 feet and extending to 7588 feet. Ultimate depth of the well is planned to be 20,000 feet, or at a bottomhole temperature of 500 C, whichever comes first. Total cost of this drilling phase was approximately $2.3 million, and funding was shared about equally between the California Energy Commission and the Department of Energy. Phase II scientific work will commence in July 1992 and will be supported by DOE Office of Basic Energy Sciences, DOE Geothermal Division, and other funding sources.

Lost circulation is the loss of drilling fluid from the wellbore to fractures or pores in the rock formation. In geothermal drilling, lost circulation is often a serious problem that contributes greatly to the cost of the average geothermal well. The Lost Circulation Technology Development Program is sponsored at Sandia National Laboratories by the U.S. Department of Energy. The goal of the program is to reduce lost circulation costs by 30-50% through the development of mitigation and characterization technology. This paper describes the technical progress made in this program during the period April, 1991-March, 1992.

For a number of years the Department of Energy has been funding research to reduce the cost of drilling geothermal wells. Generally that research has been effective and helped to make geothermal energy economically attractive to developers. With the increased competition for the electrical market, geothermal energy needs every advantage it can acquire to allow it to continue as a viable force in the marketplace. In drilling related research, there is essentially continuous dialogue between industry and the national laboratories. Therefore, the projects presented in the Program Review are focused on subjects that were previously recommended or approved by industry.

A numerical simulation is presented for a simplified model of the Long Valley geothermal system in order to elucidate the nature of the large-scale thermal structure within the system and to assess implications for the drilling program currently underway in the region. The two-dimensional model consists of three horizontal layers, the upper two of which are porous and saturated with a single phase fluid. The system is limited in horizontal extent and heated uniformly from below. An associated planar, natural convective flow is thus produced. The results of the simulation indicate the possibility of wide variations in vertical temperature profiles for the model system, depending on the locations of measurements relative to the convective cells within the layered medium. Thus it can be inferred that, during the early stages of drilling, the vertical temperature distribution may not be a reliable indicator of the presence or absence of the relatively shallow magma body which has been predicted to underlie the geothermal region.

The Interim Standard Offer Number Four Contracts (ISM), under which most of the geothermal industry is selling power (outside of The Geysers), has an initial ten year period of known fixed energy payments. In the eleventh year, the price goes to the Avoided Cost of the buying utility. The specific contract language is ''Seller will be paid at a rate equal to the utilities' published avoided cost of energy as updated and authorized by the Commission (CPUC)''. The first geothermal contract will reach the end of the initial 10 year period in early 1994, a few will end in 1995 and 1996, and the majority will end in the 1997-2000 period. This is beginning to be focused upon by the utilities, lenders and, of course, the operators themselves. The prime reason for focusing on the issue is that avoided costs of the utilities directly track the delivered cost of the natural gas, and most forecasts are showing that the price of gas in the eleventh year of the contracts will be significantly lower than the last year of the fixed period of energy payments. There are many forums in which the predication of natural gas prices are discussed. In the …

The author critiques the Exploration component of the U.S. Department of Energy (DOE) Geothermal Program Review X. The comments focus principally on the hydrothermal portion of the DOE program, but he also makes some commentary on the Long Valley Exploratory Well and Geopressured-Geothermal components of the program, as well as some general comments. Before I do that, I would like to review the current state of geothermal exploration in the United States. According to Koenig (1989, 1990) who critiqued the DOE Geothermal Program in those years, geothermal exploration in the western U.S. has been conducted in virtually all of the apparent geothermal resource areas. Many of these areas which were under exploration in the 1960s and 1970s, and were explored in part under the U.S. DOE Industry Coupled Program have progressed to commercial status in the 80s. The DOE March (1992) Draft Multi-Year Program Plan for FY 1993-1997 states that 8 out of the 14 geothermal resource areas explored under this Industry Coupled Program in the late 1970s are currently under production. I do not think we will find anyone in this room, in the geothermal industry, or in the United States that will argue with the clear and outstanding …

It's a genuine privilege for me to be here today. As Dr. Mock mentioned, I have been President of California Energy for not yet three months and have a total tenure in the industry of only one year. As a newcomer to the industry, I am honored to address this group and share my views on ''The Opportunities and Challenges for Expanding Geothermal Energy''. You will see that my outlook for our industry is generally optimistic, shaped in part, perhaps by a newcomer's enthusiasm, but largely I think by my analysis of the opportunities which are open to us as an industry. Many of you and your predecessors over the last 20 years pioneered the geothermal industry in the United States. The risks were great, the results sometimes rewarding, sometimes disappointing. Government and the private sector forged an alliance that moved the industry ahead. Developers, utilities and federal land managers worked together to bring projects on line. Government helped identify geothermal areas, in many cases doing exploration work. The geothermal pioneers had to form entirely new, multi-disciplinary teams to solve problems unique to this resource. From discovery of fields, to environmental mitigation, to management of reservoirs and all of the …

Dr. Mock began the session by paying tribute to Dr. Myron Dorfman, Professor of Petroleum Engineering at the University of Texas, who had just passed away after a protracted illness. Dr. Dorfman, more than other any individual, was responsible for bringing the geopressured-geothermal state-of-the-art to its present technological readiness for commercialization by industry. Allan Jelacic, Geosciences Team Leader, Geothermal Division, chaired the formal session and gave a historic overview of the conference that defined research needs and economic potential of the resource. First the Nevada Field Office and later the Idaho Field Office took the lead in setting research directions and managing the program. The major research activity was to flow-test ten Wells of Opportunity, provided by industry, as well as the Design Wells, of which four were drilled. Initial problems with calcium carbonate scale deposition and the safe handling and disposition of up to 30,000 barrels of geopressured brine per day were solved. A series of seminal conferences followed so that by the mid-eighties, the resource's extent and productivity were understood, and DOE's Geothermal Division was proceeding with technology transfer to industry. Allan Jelacic pointed out that currently the program is phasing down, with only three active wells remaining: …

I think it is wonderful that our Country can support research projects. Innovations and the development of cost-effective technology is a strategic issue for our industry. We all know that this is important--in fact, required to keep the industry healthy. The objective must be to continuously develop technology which will do things better for less money. This is the ultimate goal of research. I've been asked to comment on production research issues. And so, I will limit my discussion to just that. I think what we've heard in the last few days concerning cements, waste processing, and scale prediction is encouraging. In particular, the work that is being conducted on polymer cements may be of significant importance. As you may know, many parts of The Geysers and other fields are incurring high corrosion rates. The question before us is, do we plug and abandon these wells? Install hangdown strings of small diameter liner using expensive metallurgy such as Inconnel, Hastelloy or Titanium? Or, drill new wells? With current economics, it behooves them to seek the least expensive option which can extend the economic life of these deteriorating facilities. Our current option may be to run inner-liners utilizing these new polymer …

As our geothermal fields mature and the inevitable problems arise with their exploitation, it will be reservoir engineers that will evaluate our possible future courses of action in order to solve these problems. But first they must have the right tools and data. To date, the best reservoir engineering tool we have in geothermal is the reservoir simulators. The reason for this is our severe lack of definition of reservoir parameters. Within a simulation there are checks and balances on the interrelation of reservoir parameters that keep the result within certain realistic bounds. These uncertain parameters make most traditional reservoir engineering methods such as volumetrics of little use for anything beyond preliminary work. Parametric studies such as those by Mike Shook help in determining the range and sensitivity of unconstrained variables in simulator work and are valuable. However, as two non-unique simulations can yield similar results on an established field configuration, the same two can then give different results if used for investigating different future scenarios, injection cases or other what-if's. Therefore to use simulators as a development or management tool with greater confidence, a more unique solution is desired, requiring greater definition of the parameters input into the model. …

Advances in the development of new materials continue to be made in the Geothermal Materials Project. Many successes have already been accrued and the results used commercially. In FY 1991, work was focused on reducing well drilling, fluid transport and energy conversion costs. Specific activities performed included lightweight CO{sub 2}-resistant well cements, thermally conductive and scale resistant protective liner systems, chemical systems for lost circulation control, corrosion mitigation in process components at The Geysers, and elastomer-metal bonding systems. Efforts to transfer the technologies developed in these efforts to other energy-related sectors of the economy continued and considerable success was achieved. Laboratory testing of BNL-developed phosphate modified calcium aluminate cements confirmed their hydrolytic stability in 300 C brine and their resistance to chemical attack by CO{sub 2}. Specimens were found to be >20 times more resistant to carbonation than Class H cement and twice as resistant as unmodified calcium aluminate cements. Testing of thermally conductive polymer cements as potential corrosion resistant liner materials for use in heat exchanger applications was continued. Field test were conducted in flowing hypersaline brine and the results indicated scale deposition rates lower than those on a high alloy steel. Additional tests for bottoming cycle heat exchange …