This paper presents the initial results of a survey of the occurrence and characteristics of geopressured fluid resources in California using the publicly-available database involving more than 150,000 oil and gas wells drilled in the State. Of the 975 documented on-shore oil and gas pools studied, about 42% were identified as potentially geopressured. Geothermal gradients in California oil and gas fields lie within the normal range of 1°F to 2°F per 100 feet. Except for the Los Angeles Basin, there was no evidence of higher temperatures or temperature gradients in geopressured pools. The porosity of geopressured pools shows the same normal distribution as for normal pressured pools, with a mode in the range of 20 to 25%. The salinity distribution of both the geopressured and normal pressured pools appear to be bimodal, each with two peak ranges of 0 to 10,000 and 25,000 to 30,000 ppm. Compared to the U.S. Gulf Coast region, geopressured pools in California display much lower water salinities, and therefore, should have a higher solubility for methane. Geopressured pools in California occur in the depth range of less than 1,000 feet to more than 18,000 feet. The modal depth of geopressured pools in California is 2,000 …

There are four long-term exploited geothermal fields in Kamchatka: one steam-water field Pauzhetka (south of Kamchatka peninsula) and three hot water fields: Paratunka (near by town of Petropavlovsk-Kamchatsky) and Esso and Anavgay (center of peninsula). Pauzhetka and Paratunka fields are exploited during almost 28 years. Esso and Anavgay fields are exploited during 25 years. In Pauzhetka 11 MWe geothermal power plant work and on the other fields thermal energy of hot water is directly used. Kamchatka region satisfies energetic demands mainly by organic imported fuels. At the same time electricity produced by geothermal fluids constitutes less than 2 per cent of total region electricity production, and thermal energy produced by geothermal fluids constitutes less than 3 per cent of total region thermal energy production. The main reasons of small geothermal portion in the energy production balance of Kamchatka are briefly discussed. The geothermal development reserves and perspectives of geothermal energy use increase in Kamchatka are outlined.

A method for determining the size of a crack induced by hydraulic fracturing is presented. The procedure is based on the measurement of the crack opening displacement and the fracture mechanics approach. The proposed method has been tested by conducting laboratory small-scale hydraulic fracturing tests on a granite. It is shown from the preliminary tests that the method provides a reasonable prediction of experimentally observed crack sizes.

This study presents a general solution for the radial flow of tracers in naturally fractured reservoirs. Continuous and finite step injection of chemical and radioactive tracers are considered. The reservoir is treated as being composed of two regions: a mobile region where longitudinal dispersion and convection take place and a stagnant region where only diffusion and adsorption are allowed. Radioactive decay is considered in both regions. The model of this study is thoroughly compared to those previously presented in literature by Moench and Ogata, Tang et al., Chen et al., and Hsieh et al. The solution is numerically inverted by means of the Crump algorithm. A detailed validation of the model with respect to solutions previously presented and/or simplified physical conditions solutions (i.e., homogeneous case) or limit solutions (i.e., for short times) was carried out. The influence of various dimensionless parameters that enter into the solution was investigated. A discussion of results obtained through the Crump and Stehfest algorithm is presented, concluding that the Crump method provides more reliable tracer concentrations.

As a part of a full scale production test, a long term tracer test was performed in the Thelamork low temperature geothermal system, in N-Iceland. The tracer test was aimed at recovering the transport properties of fractures connecting the injection and production wells. Hence, the estimated parameters might be used in determining the performance of the system under various injection schemes. A qualitative evaluation the tracer return profile showed the presence of strong recirculation effects. In addition, the return profile indicated that the medium appears to be highly dispersive. Earlier modelling studies employed a one-dimensional two path model to match the return profile and substituted the properties of the major path in the Lauwerier model to estimate the thermal breakthrough time. However, the two path model estimates a very large dispersive tiansport almost equal to the convective transport. This large dispersivity necessitates adding a dispersive heat transport term in the Lauwerier model and as a result reduces the Lauwerier thermal breakthrough time almost to half. Considering the injection and production rates, we used a more accurate one-dimensional five-path model in this work. This model infers a smaller dispersivity and leads to a greater breakthrough time than the two path model, …

Japan is scarce in domestic natural resources. In fact, the degree of dependence on imports of basic raw materials is quite high. This paper describes primary energy supply as a background to the status of geothermal energy developments, and geophysical well logging in geothermal wells. 3 refs., 5 tabs., 5 figs.

Until recently, geothermal reservoir simulators use flat interface thermodynamics to determine the thermodynamic state of the reservoir. Development of new simulators and the modification of existing ones has now incorporated the physics of curved interface thermodynamics. These simulators account for the effects of sorption and capillary forces. The simulators GSS and TETRAD were used to simulate the performance of a hypothetical vapordominated geothermal reservoir. GSS is a simulator specifically developed to account for adsorption by using adsorption isotherms. On the other hand, TETRAD is a commercial simulator that was modified to account for vapor pressure lowering by using capillary pressure relations. GSS and TETRAD yielded similar results. Thus, the two formulations being used to account for curved interface thermodynamics are practically equivalent. Areas for improvement of both GSS and TETRAD were identified. The hysteresis and temperature dependence of sorption and capillary properties are issues that are needed to be addressed.

A long term interference test was conducted under conditions of multiwell variable flow rate at Takigami for about ten months in 1987. The test data have been analyzed with an on-line analysis method on the basis of the linesource solution. This method employs Kalman filtering to process the data and then provides the best estimates of reservoir transmissivity and storativity when a new pressure data at an observation well becomes available. The pressure changes measured at seven observation wells have been analyzed with the present method using an infinite reservoir model. The data from one observation well have been further analyzed assuming a presence of a linear boundary. Performances of the parameters estimated for different reservoir models are compared. Fairly good estimates of reservoir parameters are obtained on the basis of an infinite reservoir model for two wells using the entire pressure data whereas for other five wells using a part of the pressure data.

The Third Workshop on Geothermal Reservoir Engineering convened at Stanford University on December 14, 1977, with 104 attendees from six nations. In keeping with the recommendations expressed by the participants at the Second Workshop, the format of the Workshop was retained, with three days of technical sessions devoted to reservoir physics, well and reservoir testing, field development, and mathematical modeling of geothermal reservoirs. The program presented 33 technical papers, summaries of which are included in these Proceedings. Although the format of the Workshop has remained constant, it is clear from a perusal of the Table of Contents that considerable advances have occurred in all phases of geothermal reservoir engineering over the past three years. Greater understanding of reservoir physics and mathematical representations of vapor-dominated and liquid-dominated reservoirs are evident; new techniques for their analysis are being developed, and significant field data from a number of newer reservoirs are analyzed. The objectives of these workshops have been to bring together researchers active in the various physical and mathematical disciplines comprising the field of geothermal reservoir engineering, to give the participants a forum for review of progress and exchange of new ideas in this rapidly developing field, and to summarize the effective …