The stabilities of several tracers were tested under geothermal conditions while injection-backflow tests were conducted at East Mesa. The tracers I and Br were injected continuously while SCN (thiocyanate), B, and disodium fluorescein were each injected as a point source (slug). The tracers were shown to be stable, except where the high concentrations used during slug injection induced adsorption of the slug tracers. However, adsorption of the slug tracers appeared to ''armor'' the formation against adsorption during subsequent tests. Precipitation behavior of calcite and silica as well as Na/K shifts during injection are also discussed.

We have searched for the production of likesign dilepton events (nu/sub ..mu../ + Ne ..-->.. ..mu../sup -/ + e/sup -/ + ...) in a wideband neutrino beam at Fermilab using the 15-ft bubble chamber. We observe no signal above the background arising from conventional sources. We set 90% confidence level upper limits for the production rates of (nu/sub ..mu../ + Ne ..-->.. ..mu../sup -/ + e/sup -/ + ...)/ (nu/sub ..mu../ + Ne ..-->.. ..mu../sup -/ + ...) < 0.76 x 10/sup -4/ and (nu/sub ..mu../ + Ne ..-->.. ..mu../sup -/ + e/sup -/ + ...)/ (nu/sub ..mu../ + Ne ..-->.. ..mu../sup -/ + e/sup +/ + ...) < 5.3 x 10/sup -2/.

Downhole logging and workover operations on 12-20 year old wells in several high temperature, liquid-dominated geothermal fields in New Zealand has shown that severe corrosion has commonly occurred in the production casing string where this is unprotected by larger diameter casings. To date corrosion products from only one well have been examined in detail. These indicate that corrosion attack commences at the outer casing wall and continues at a rate as great as 0.8mm/year. Rapid corrosion has been attributed to neutral or slightly acid high bicarbonate waters formed by the absorption of steam and gas into shallow aquifers not directly connected to the deeper, high chloride reservoir.

The FRACSL flow and transport code is under development as part of an effort to improve reservoir characterization techniques. The present version simulates a two-dimensional, isothermal reservoir composed of a global fracture network imbedded in a porous media. FRACSL simulates the hydraulic response of a reservoir to injection or backflow. The code simulates the movement of injected tracers within the reservoir by adding advective and random dispersive motions of discrete particles. FRACSL has been benchmarked against theoretical flow and transport responses in simple systems. It has been used to simulate a benchscale physical model and to correlate flow and dispersion data from the East Mesa Hydrothermal Injection Test Program. Correlation of East Mesa data has provided an estimate of an anisotropic hydraulic conductivity, a natural drift in the reservoir, and dispersivity.

A large body of field data from Larderello shows striking temporal correlations between decline of well flow-rate, produced gas/steam ratio, chloride concentration and produced vapor fraction. The latter is inferred from measured concentrations of non-condensible gases in samples of well fluid, using chemical phase equilibrium principles. Observed temporal changes in the vapor fractions can be interpreted in term of a ''multiple source'' model, as suggested by D'Amore and Truesdell (1979). This provides clues to the dynamics of reservoir depletion, and to the evaluation of well productivity and longevity.

This paper reviews research in the United States and Japan on structural materials for high-field superconducting magnets. Superconducting magnets are used for magnetic fusion energy devices and for accelerators that are used in particle-physics research. The cryogenic structural materials that we review are used for magnet cases and support structures. We expect increased materials requirements in the future.

The purpose of the study is to develop a simplified model to match past performances of a vapor-dominated geothermal reservoir and to predict future production rates and ultimate reserves. The data are fictitious, but are based on real data. A lumped parameter model was developed for the reservoir that is similar to the model developed by Brigham and Neri (1979, 1980) for the Gabbro zone, and a deliverability model was developed to predict the life and future producing rate declines of the reservoir. This report presents the development and results of this geothermal reservoir analysis.

Analysis of an extended flow test of well ST-1 on the flanks of Makushin Volcano indicates an extensive, water-dominated, naturally fractured reservoir. The reservoir appears to be capable of delivering extremely large flows when tapped by full-size production wells. A productivity index in excess of 30,000 lb/hr/psi implies a phenomenal permeability-thickness product, in the range of 500,000 to 1,000,000 md-ft. The flowing bottomhole (1,949-foot) temperature of the fluid is 379 F, which is lower than the measured static temperature at that depth (395 F). This phenomenon, coupled with an observed static temperature gradient reversal from the maximum 399 F observed at 1,500 feet, indicates that the reservoir proper is located some distance from the well. presumably it is at a temperature slightly lower than 379 F and communicates with the wellbore via a high conductivity fracture system. A material balance calculation yields an estimate of reserves that are capable of sustaining all of the present power needs of the island (13 {+-} MW peak) with a geothermal power plant for several hundred years. Theoretically, a single large diameter well at the site of ST-1 could satisfy this requirement.

We report results of simulations of stimulated Brillouin backscatter in which we see the second spatial harmonic of the ion density fluctuation and compare with linear, fluid theory. We also describe examples of the competition between Raman and Brillouin backscatter. 21 refs., 3 figs.

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Reinjection of waste hot water is commonly practiced in most geothermal fields, primarily as a means of disposal. Surface discharge of these waste waters is usually unacceptable due to the resulting thermal and chemical pollution. Although reinjection can help to main reservoir pressure and fluid volume, in some cases a decrease in reservoir productivity has been observed. This is caused by rapid flow of the reinjected water through fractures connecting the injector and producers. As a result, the water is not sufficiently heated by the reservoir rock, and a reduction in enthalpy of the produced fluids is seen. Tracer tests have proven to be valuable to reservoir engineers for the design of a successful reinjection program. By injecting a slug of tracer and studying the discharge of surrounding producing wells, an understanding of the fracture network within a reservoir can be provided. In order to quantify the results of a tracer test, a model that accurately describes the mechanisms of tracer transport is necessary. One such mechanism, dispersion, is like a smearing out of a tracer concentration due to the velocity gradients over the cross section of flow. If a dispersion coefficient can be determined from tracer test data, the …

Mokai is a recently-explored geothermal field in New Zealand. After drilling 6 wells, it is clear that there exists an extremely productive reservoir. The future exploration and development options are evaluated to find the most economic path to a developed resource. The basic tradeoff considered is between additional proving effort, and the consequent expense and, more importantly, delay. For fields of the generally very productive type found in New Zealand, comparatively little proving appears justified.

There have been two major high-temperature geothermal field developments in Iceland in the last decade; Krafla in the north-east, and Svartsengi in the south-west. These and other geothermal developments have recently been reported by Palmason et al. The Krafla field will not be discussed here, but details about the field are available in Stefansson and the power plant in Eliasson et al. Several reservoir engineering studies of the Krafla field have been published. The Svartsengi field is one of several fields on the Reykjanes Peninsula in south-west Iceland. About 15 km west of Svartsengi, on the tip of the Peninsula, the Reykjanes field is now under development, primarily for seawater chemicals production. The recently drilled Eldvorp field is located in line between these two fields, about 5 km west of Svartsengi. There are also several fields to the east of Svartsengi, at 15-20 km distance. The Svartsengi, Eldvorp, and Reykjanes fields exist in the same tectonic-volcanic environment, and are surrounded by similar geohydrological conditions, as discussed by Georgsson; see also Gudmundsson et al. and Franzson. Optimum development of these and other fields on the Reykjanes Peninsula, requires an understanding of their depletion behavior with time; that is, how the reservoir …

The boundaries of reservoir fluid convection cells are discreet and intricate zones, commonly sealed or reduced in permeabilities, which are often quite readily identifiable in many hydrothermal systems. Cell boundaries in the Geysers Steam Field are more vague; however, they are gradually being revealed by cumulative and extensive wellbore data. A profound example of a type of boundary has been revealed by drilling in one area of the steam field. A proposed model utilizes a sericitic alteration scheme to establish cell self-sealing. Mineralogical, permeability, and temperature properties all coincide so as to allow formation of a boundary model. This reinforces previously held views that the reservoir cell rock and hydrothermal system are greatly out of equilibrium. Such similar phenomena are suggested from drilling experiences in other parts of the steam field. Considerably, more work is required to better define and comprehend the nature and location of reservoir cell boundaries within the Geysers Steam Field.

This paper presents the combined approaches of reservoir geology and engineering to a geothermal field where geological characteristics are highly complex and heterogeneous.Especially,the concrete approaches are discussed for the case of geothermal reservoir performance studies with a developed numerical model, by showing example cases accompanied with reinjection of produced disposal hot water into underground in an object geothermal reservoir. This combined approach will be a great help in solving complicated problems encountered during the development of a geothermal field.

Starting from the basic laws of conservation of mass and energy, the differential equations that represent the thermodynamic behavior of a simplified geothermal reservoir are derived. Its application is limited to a reservoir of high permeability as it usually occurs in the central zone of a geothermal field. A very practical method to solve numerically the equations is presented, based on the direct use of the steam tables. The method, based in one general equation, is extended and illustrated with a numerical example to the case of segregated mass extraction, variable influx and heat exchange between rock and fluid. As it is explained, the method can be easily coupled to several influx models already developed somewhere else. The proposed model can become an important tool to solve practical problems, where like in Los Azufres Mexico, the geothermal field can be divided in an inner part where flashing occurs and an exterior field where storage of water plays the main role.

A large number of studies have been published in the past 10 to 12 years dealing with solute transport in fractured media. The vast majority of this work deals with solute transport in single fractures. Much of this work has been motivated by the need for a repository for storage of nuclear wastes that is safely sequestered from man and the environment. A number of papers deal with dual porosity aquifers, where fractures occur in a rock that also contains primary porosity. Usually, the permeability of the matrix blocks is considered insignificant relative to the permeability of the fracture system. The matrix blocks do not participate in fluid flow through the rock, but can be involved in heat transfer and solute retardation phenomena. Diffusive transfer between fractures and the rock matrix is the mechanism for heat transfer and retardation of solutes. None of the approaches deals with advective transport between fracture and matrix. Solute transport in the fracture is either by advection alone or by advection and dispersion based on a one dimensional solution to the advection-dispersion equation. Research at EG and G is currently oriented at perfecting techniques for simulation of this type of dual permeability fracture system. Simulation …

We have devised a simple method to assess the natural thermodynamic state of two-phase reservoirs. This is usually a complex task. The method is based on inferring sandface flowing pressures and enthalpies from production output (deliverability) curves, and then extrapolating to shutin conditions in the pressure-enthalpy plane. The method was applied to data from 10 wells of the Los Azufres geothermal field. Comparison of the results with measured pressures and temperatures showed that the method is reliable. We present detailed thermodynamic properties of the unperturbed reservoir fluid in the neighborhood of the wells studied, in tabular form. Moreover, we present a match to these results with a very simple model that allows reasonable estimates of natural thermodynamic conditions as functions of height above sea level. The present results have important implications for the assessment of the fluid reserves, which are suggested to be greater than previously thought.

We have refined a method used previously by several authors to estimate water-steam relative permeabilities. Our version provides also reasonable estimates of the corresponding saturations. It relies on production output data obtained by means of short tests. This constitutes a distinct advantage over the previous variants, which require long-term production data, because it allows early accurate assessments of reservoir reserves and producibility. Applying the refined version to data from 5 Cerro Prleto wells we obtained the corresponding relative permeabilities. These results indicate that the relative permeabilities are remarkably homogeneous over a wide area of the field, and over a considerable fraction of the reservoir thickness. They also provide independent evidence that fracture flow is important in Cerro Prieto. Finally, comparison of our results with those found for Wairakei shows that the relative permeabilities of geothermal reservoirs can be sensitively site-dependent.

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The Pauzhetka hydrothermal system is located in a volcano-tectonic depression near active volcanic centers. Temperatures at depths of 300-800 m are 180-210 C. The natural discharge of the hydrothermal system includes the discharge of the Pauzhetka springs and a concealed discharge in the bed of the Pauzhetka River (95 kg/s) and the steam discharge in the Kambalny Ridge (15 kg/s). Only the upper part of geothermal reservoir was penetrated by drillholes (up to 1200 m), therefore they have used a mathematical modeling to assess the conditions of water and heat feeding of the hydrothermal system. The hydrothermal system belongs to a linear fracturing zone of NW trend, therefore the two-dimensional model was used in the calculations. It has been defined that (1) the source of heating is a magma chamber located at a shallow depth; (2) the heat and mass transfer in the geothermal reservoir is defined by free and forced hydraulic convection, (3) the conductivity coefficient of a linear fracturing zone is 400-600 m{sup 2}/day, its width is 2 km and length is 10 km, and (4) the water feeding is defined by infiltration in the recharge area. Calculations of temperature and velocity fields agree with real data obtained …

Extensive study of the Cerro Prieto geothermal field has provided much geologic and thermodynamic data of its structurally-complex, liquid-dominated reservoir. Several of the studies investigated the resource characteristics of fluid and energy flow. An early report by Mercado (1975) showed that the heat source for the part of the reservoir under development, now called Cerro Prieto I (CPI), originated in the eastern part of the field. Subsequent studies confirmed the flow of hot water from the east. A summary of several experimental and numerical studies of fluid and energy transport in the field was given by Lippmann and Bodvarsson (1983). The hydrogeologic model of Halfman et al. (1982) shows hot-water flow from the east divided into a shallow (alpha) aquifer at about 120Om and a deeper (beta) aquifer at about 170Om depth. A cross section along an east-west direction shows a central upflow to the two aquifers and uncertain geology beyond the western border of the field near well M-9. It also shows a fault dividing the line of border wells at M-29 from the inner wells at M-25 to the east. The hydrogeology of the field was described by Sanchez and de la Pena (1981) as an alluvial unit …

One of the major concerns of electric utilities in installing geothermal power plants is not only the longevity of the steam supply, but also the potential for changes in thermodynamic properties of the resource that might reduce the conversion efficiency of the design plant equipment. Production was initiated at Los Azufres geothermal field with wellhead generators not only to obtain electric energy at a relatively early date, but also to acquire needed information about the resource so that plans for large central power plants could be finalized. Commercial electric energy production started at Los Azufres during the summer of 1982 with five 5-MWe wellhead turbine-generator units. The wells associated with these units had undergone extensive testing and have since been essentially in constant production. The Los Azufres geothermal reservoir is a complex structural and thermodynamic system, intersected by at least 4 major parallel faults and producing geothermal fluids from almost all water to all steam. The five wellhead generators are associated with wells of about 30%, 60%, and 100% steam fraction. A study to compile existing data on the chemical and reservoir conditions during the first two years of operation has been completed. Data have been compiled on mean values …