RODCON, a finite difference computer code, was developed to calculate the internal temperature distribution of the fuel rod simulator (FRS) for the Core Flow Test Loop (CFTL). RODCON solves the implicit, time-dependent forward-differencing heat transfer equation in 2-dimensional (Rtheta) cylindrical coordinates at an axial plane with user specified radial material zones and surface conditions at the FRS periphery. Symmetry of the boundary conditions of coolant bulk temperatures and film coefficients at the FRS periphery is not necessary.

A new concept for a dump for the ion and neutral beams used in the controlled nuclear fusion program uses thin sheets of a refractory metal such as tungsten formed into troughs having semi-circular cross sections. High-velocity water flowing circumferentially removes heat by subcooled nucleate boiling. Possible advantages are modular construction, lower water-pumping power, and a lower pressure drop than in conventional beam dumps. An example design calculation is shown for a dump capable of absorbing an incident flux of 10 kW/cm/sup 2/.

Compliance with the latest regulatory requirements addressing disposal of radioactive, hazardous, and sanitary solid waste requires the application of numerous qualitative and quantitative criteria in the selection, design, and operation of solid waste management facilities. Due to the state of flux of these regulatory requirements from EPA and NRC, several waste management options were identified as being applicable to the management of the various types of solid waste. This paper highlights the current regulatory constraints and the design and operational requirements for construction of both storage and disposal facilities for use in management of DOE-ORO solid waste. Capital and operational costs are included for both disposal and storage options.

The purpose of this study was to systematically investigate effects of temperature and fluid composition on the permeability of quartz sandstones. We have concentrated our initial efforts on the time and flow dependence at 2 elevated temperatures (100°C, 200°C).

Two hot dry rock (HDR) geothermal energy reservoirs were created by hydraulic fracturing of granite at 2.7 t o 3.0 km (5000 to 10000 ft ) at the Fenton Hill site, near the Valles Caldera in northern New Mexico. Both reservoirs are research reservoirs, in the sense that both are fairly small, generally yielding 5 MWt or less, and are intended to serve as the basic building blocks of commercial-sized reservoirs, consisting of 10 t o 15 similar fractures that would yield approximately 35 MWt over a 10 to 20 yr period. Both research reservoirs were created in the same well-pair, with energy extraction well number 1 (EE-1) serving as the injection well, and geothermal test well number 2 (GT-2) serving as the extraction, or production, well. Evaluation of the second reservoir was accomplished in two steps: (1) with a 23-day heat extraction experiment that began October 23, 1979, the results of which are described by Murphy (1980), and (2) a-second, longer-term heat extraction experiment still in progress, which as of November 25, 1980 has been in effect for 260 days. The results of this current experiment are compared with earlier experiments.

At present in Mexico, geothermal energy is receiving a great impulse due to the excellent results obtained in the Cerro Prieto geothermal field, in which a geothermoelectric plant is operated. This plant has four units of 37.5 MW each, with a total capacity of 150 MW, and under program 470 MW more by 1984. The Government Institution, Comisi6n Federal de Electricidad, is in charge of the exploration and exploitation of geothermal fields as well as construction and operation of power plants in Mexico. By this time CFE has an extensive program of exploration in the central part of Mexico, in the Eje Neovolcdnico. In this area, several fields with hydrothermal alteration are under exploration, like the Michoac6n geothermal area, where Los Azufres geothermal field is being developed. Seventeen wells have been drilled and twelve of them presented excellent results, including two dry steam wells. In other areas, such as Arar6, Cuitzeo, San Agustln del Maiz,Ixtldn de Los Hervores and Los Negritos, geological, geophysical and geochemical explorations have been accomplished, including shallow well drilling with good results. Another main geothermal area is in the State of Jalisco with an extension of 5,000 m2, where La Primavera geothermal field shows a lot …

Well test analysis offers a rapid way to perform an initial assessment of geothermal systems. Well testing includes both pressure drawdown and buildup testing, and interference testing. Development of new well test analyses receives major emphasis in the Stanford Geothermal Program. During the year, quite a few studies were completed, and reports and papers presented on a variety of well test analysis methods. The paper summarizes some of the more important results.

The main purpose of this study is to analyze pressure drawdown and buildup data to evaulate formation parameters. In this connection, we note that the, flow periods 1 and 2 were too short (13 minutes and 184 minutes respectively) to give meaningful data for analysis purposes. Also, flow data for part of flow period 3 and pressure buildup data for practically all of buildup period 4 are missing. The complete flow and pressure drawdown/buildup data are, however, available for flow/shutin period S (flowing time - 10.5 days, shutin time - 20 days). For the aforementioned reasons, our analysis will be primarily concerned with the flow/shutin period 5.

Ward (1980) described the exploration of the Okoy geothermal field. Resistivity surveying using Schlumberger traverses has covered an area of approximately 800 km2 in the southern part of the Island of Negros. Hot springs and other thermal manifestations occur in the Okoy valley, Valencia and at Tabac Magaso, Dauin. Initial shallow exploratory drilling indicated a possible sub-surface flow of hot water in the Okoy valley. Further deep exploratory drilling to the West has located two high temperature reservoirs.

Identification of production zones in a fractured or faulted qeotherrnal well is quantitatively difficult. Temperature and spinner surveys along with flow tests are the techniques generally used to identify and describe these fractured zones during production testing. These techniques generally do not describe the production zones in any detail and they miss or bypass potential zones of production when fractures have been closed or plugged during the drilling process. These latter zones could possibly be stimulated (hydraulic fracturing, acidizing, explosive fracturing) and brought into production if all the fracture zones could be identified and described. Interpretation techniques using wireline logs show promise in identifying and describing fractured (open and closed) zones in geothermal wells. The strategy described in this paper on two different geothermal wells (the hot dry rock well and the Surprise Valley well) used a trial and error basis to outline and define the interpretation techniques that work best in each case. Fracture zones are identified that are both open and closed and this type of information gives a better estimation of reservoir size, flow control and reservoir life (production potential) from geothermal wells.

The Pleasant Bayou #2 Geopressured-Geothermal test well was completed in the summer of 1979. The C sand of the Frio formation was selected for completion on the basis of core analysis, well logs, and drill stem tests. The purpose of this paper is to summarize the results of the short term production tests run on the Pleasant Bayou #2 well during 1979 and the Fall of 1980. These tests were analyzed using conventional transient pressure test analysis methods. The most significant test run during 1979 was a ten day drawdown test from December 3 to December 14 followed by a 20 day buildup period, during which reservoir pressure response was observed. After a hiatus of nine months, a second production test was conducted over a period of 45 days beginning on September 16, 1980. The well was shut in on October 31, 1980. Pressure buildup data continues to be monitered. Both production tests indicate a formation permeability of 200 millidarcies. The presence of a permeability interruption located approximately 3700 feet from the wellbore is also suggested by these tests. During the last production test, a producing gas-water ratio of 20 standard cubic feet per barrel of produced water was observed. …

A necessary first step in resolving differences and in evaluating the usefulness of numerical simulators for geothermal reservoir analysis is the comparison of simulator results for a set of well-specified problems involving processes applicable in reservoir analysis. Under the direction of DOE'S Geothermal Reservoir Engineering Management Program (GREMP), a set of six test problems has been developed in an attempt to meet this need. The problem set covers a range of reservoir situations including single- and two-phase flow under 1, 2, and 3 dimensional conditions. Each problem has been test run to insure that the parameter specifications will yield workable solutions, and in several cases analytical solutions are available for comparison. Brief descriptions of the problems are given in each problem, the desired grid and time-step sizes were specified to minimize differences in results due to numerical discretization.

All numerical simulators of geothermal reservoirs depend upon an accurate representation of the thermodynamics of steam-water systems. These relationships are required to render tractable the system of balance equations derived from the physics of flow through porous media. While it is generally recognized that the steam-water system (i.e. two phase) is not in thermodynamic equilibrium, equihbrium thermodynamics are employed in its description. In this paper, we present an alternative view based on non-equilibrium thermodynamics. The underpinnings of this approach are found in a branch of topology generally referred to as "catastrophe theory". [Thom, 1975]

The authors present a three-dimensional model for reservoir simulation to show some behaviors of fluid flow in a geothermal reservoir, assuming water influx and heat conduction from heat sources under the reservoir.

This paper is devoted to the discussion of the wellbore model and its describing equations, comparison between the computed and measured pressures and the effect of measured wellhead parameters on the downhole pressures in the well. Finally a wellbore model with multiple inside diameters is discussed and the effect of well scaling on the bottom hole pressures is studied.

Examples of two-phase pressure transient analysis are given, for injection and discharge. Transients measured in KA28 are used to identify the fluid feeding the well and to measure permeability.

Little information has been published on the hydrothermal alteration minerals occurring at depth in the Geysers steam field, California. Steiner (1958) reported the occurrence of wairakite from a well; McNitt (1964) identified pyrite, sericite, calcite, quartz, siderite, apatite and chlorite in cores of Franciscan graywacke and greenstone. Recently, Union Oil Geothermal Division furnished a set of well cores from the cap rock overlying the steam reservoir for geophysical studies (Lockner -e t -a l . , 1980). Cores of metagraywacke and greenstone from 4 wells were compared to unaltered Franciscan metagraywacke from surface exposures. Several previously unreported alteration minerals were found in the cored rocks, including epidote, tremolite-actinolite, prehnite and tourmaline. This note describes the observed alteration minerals and some of the factors that controlled their growth.

Most recent interest in the injection of cold water into a geothermal reservoir has been related to the disposal of geothermal brines. Injection also offers the potential benefit of prolonging the useful life of a vapor-dominated system by providing additional water to extract energy out of the rock matrix. In a liquid-dominated reservoir injection may help to maintain pressures near the production wells by pushing the hot water toward them and preventing too much local boiling. Pressure maintenance can also be achieved for superheated steam zones, because injection will cause pressures to increase towards the saturation pressure (Schroeder et a l . (1980)). The general physical principles governing these processes are understood but no quantitative information is available. The present work is aimed at helping to improve the qualitative and quantitative understanding of injection into a geothermal reservoir by considering a few idealized problems. First a vapor-dominated, single layer reservoir is considered, next a vapor-dominated, four layer reservoir, and finally a liquid-dominated, single layer reservoir. In each case varying injection rates are considered and in some cases the injectionis changed at different times.

An estimate of t h e chemistry of the fluid within a geothermal reservoir is required to establish the geological source and the possible environmental impact of the fluid as well as scaling and corrosion problems which might develop during production. While a detailed analysis of the chemical composition of a geothermal fluid can only be obtained from a water sample, an estimate of the total dissolved solids (TDS) in equivalent sodium chloride (NaCl) concentration can be obtained from well logs. TDS can also be useful in geological correlation between wells. TDS can be determined directly from a pulsed neutron log and a porosity log, (if the type of formation is known), or from the water resistivity, R{sub w}, and the temperature, T. Three approaches are used to find R{sub w}, and thus TDS. The first method uses a dual induction focused log and information from the log heading. Next, is found by employing an electrical log and a porosity log. The last approach utilizes the spontaneous potential log and header data. Examples are provided to illustrate the techniques described which utilize calculated values of R{sub w} to determine TDS.

The work presented herein is a study of the effect of temperature on the absolute permeability to distilled water of unconsolidated sandstones at one confining pressure. The absolute permeability to distilled water of Ottawa silica sand was not dependent on the temperature level.

The main purpose of this work is to show that it is possible to calculate the sandface flowrate given wellhead conditions and the downhole pressure transients. It is not necessary t o know anything about the reservoir itself. First, it is of interest to look at the nonuniform pressure changes in the well, and to illustrate nonisothermal effects on pressure transient data.

The large number of nonproductive wells lying along the northern and western margins of the Larderello field have indicated some boundaries of the productive area but have also prevented us, so far, from fully understanding the pheiomena controlling the behavior of the geothermal system in these areas. In 1980 ENEL re-opened some wells that had been shut-in immediately after drilling, thus offering us the possibility to complete the geochemical picture by means of numerous samplings of steam, gas and water in both productive and nonproductive wells. Some recent physical parameters measured in nonproductive and abandoned wells also helped in further defining the hydrogeological and thermal situation.

The Raft River 5 MW power plant will be on-line some time this spring. During testing of the supply and injection system prior to plant start-up and during testing of the plant itself, data can be collected and used to calibrate computer models, refine predicted drawdowns and interference effects, monitor changing temperatures, and recalculate reservoir parameters. Analytic methods have been used during reservoir testing at Raft River to calculate reservoir coefficients. However, anisotropy of the reservoir due t o fractures has not been taken into account i n these calculations and estimates of these coefficients need to be refined. From refined estimates of reservoir coefficients better predictions of interference effects and long-term drawdown in the wells can be made. In conjunction with the USGS, Faust and Mercer's 3-D finite difference model has been used to simulate the Raft River geothermal field. Intera used a 2-D simulator to predict temperatures, pressures over 30 years and movement of dissolved solids in the reservoir. Data collected during production of the field will be compared to these simulations and the models refined.

We describe simulation of the transient evolution of a "cold" hydrothermal system into a steady-state partially vapor-dominated system. In our study we have neglected the effects of salts and gases and have assumed that rock properties are time independent and homogeneous within each part of the system. Despite these simplifications we believe that our model demonstrates the essential features of a natural hydrothermal convection system (NHCS).