22 Matching Results

Search Results

Advanced search parameters have been applied.

1982 THERMAL SHALLOW RESERVOIR TESTING

Description: An extensive study of the Thermal Shallow Reservoir at The Geysers was performed in 1982 to improve our understanding of the source and flow patterns of steam in the shallow anomaly and how they relate to the Thermal 4 blowout. This project included gathering and analyzing pressure transient, enthalpy, tracer and chemical data and developing a reservoir model that was consistent with this data. Following the pressure transient testing and analysis, a convection-plume with lateral-flow model was proposed. Subsequent analysis of enthalpy, tracer and chemical data corroborated this model. The high flowrate wells--Thermal 4, Thermal 10, Thermal 11 and Magma 1--produce from the high-pressure, high-permeability upflow zone. The source of this upflow is a limited fracture system connecting the shallow anomaly with the underlying main reservoir. The outlying low-pressure, low-permeability wells are supplied by lateral flow of steam from the central area. The pressure gradient from the core to the periphery is caused by condensation in the flanks.
Date: January 22, 1985
Creator: Mogen, P.; Pittinger, L. & Magers, M.
Partner: UNT Libraries Government Documents Department

FIELD DEVELOPMENT AND POWER GENERATION IN KIZILDERE, TURKEY

Description: Turkey is classified among countries which have high geothermal energy potential. Geological and geophysical explorations are continuing in promising areas. However primary emphasis was given to Western Anatolia during the last decade. As a result of these efforts Kizildere field was developed and power plant was put into operation in February 14, 1984. This paper summarizes the power plant, production problems encountered in wells during the last nine months and future field development plans.
Date: January 22, 1985
Creator: Okandan, E, & Polat, T.
Partner: UNT Libraries Government Documents Department

ASPECTS OF DOE'S CURRENT GEOTHERMAL PROGRAM

Description: In bringing you up to date on DOE's geothermal R and D programs, they are going to emphasize first those elements that may be of special interest to a reservoir engineering audience, because the activities in support of an improved understanding of hydrothermal reservoirs deserve attention. Reservoir definition, brine injection, and reservoir stimulation technologies are major elements of the Hydrothermal Research Program, and in total they account for nearly 50% of the fiscal year (FY) 1985 hydrothermal research budget. These elements fall into the essential R and D category; that is, while some basic technologies have been borrowed from the petroleum industry for geothermal service, they are often ill-suited to geothermal requirements, and cannot be used without significant technological innovations. Into this category fall the current reservoir technology, brine injection, and reservoir stimulation projects that are listed in Table 1. The reservoir technology projects include: (1) development of methods for characterizing and mapping reservoir parameters, processes, and spatial dimensions; (2) development of methods to predict and monitor reservoir changes from fluid extraction; (3) evaluation of existing methods and development of new methods for predicting the location and mapping faults and fractures in geothermal reservoirs; and (4) testing of new analysis techniques using field case studies. Brine injection projects include: (1) development of physical and mathematical models to determine the behavior of geothermal reservoirs during injection; (2) tracer testing to determine rapid flow paths between wells; and (3) analysis of pressure responses in the field to injection into one or more wells.
Date: January 22, 1985
Creator: Mock, J.E. & Marshall, J.R.
Partner: UNT Libraries Government Documents Department

THE NESJAVELLIR HIGH TEMPERATURE GEOTHERMAL FIELD IN ICELAND

Description: The Nesjavellir High Temperature Geothermal Field is located in the Northern part of the Hengill Geothermal Area, which has been estimated to be one of the largest geothermal areas in iceland. Drilling started at Nesjavellir some 20 years ago with five wells. In 1982 a renewed exploration phase began and five additional wells have been drilled during the last three years. The pressure distribution within the geothermal system is very inhomogeneous in both horizontal and vertical directions. Variations in temperature are also considerable. The highest pressure and temperature is found in the southwestern part of the investigated area and both pressure and temperature decreases towards northeast. There seem to be four different zones of pressure potential in the system, which require the existence of both horizontal and vertical barriers in the system. Some parts of the geothermal system are in two-phase condition whereas other parts are in single phase liquid condition. The chemical composition of the fluid seem to be relatively uniform and a common origin of the fluid is assumed. The transmissivity of wells is in the range (1,3-3,5) 10{sup -8} m{sup 3}/Pa {center_dot} s whereas the flowing enthalpy ranges from 1200-2100 kJ/kg. The thermal output of wells are 40-60 MW. The geothermal system at Nesjavellir shows a high degree of three-dimensional variation, but a simple conceptual model described in the paper, seem to be in agreement with all observation made so far in the field.
Date: January 22, 1985
Creator: Stefansson, V.
Partner: UNT Libraries Government Documents Department

Experimental Determination of Tracer Dispersivity in Fractures

Description: 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 fracture width can be estimated. The purpose of this project was to design and construct an apparatus to study the dispersion of a chemical tracer in flow through a fracture.
Date: January 22, 1985
Creator: Gilardi, J. & Horns, R.N.
Partner: UNT Libraries Government Documents Department

THE HOHI GEOTHERMAL AREA, KYUSHU, JAPAN

Description: Geophysical data from surface measurements and downhole pressure/temperature data in northern Kyushu centered around Mount Waita are examined. The study area includes the geothermal fields supplying steam for the Hatchobaru and Ohtake power stations, but also extends a considerable distance to the northwest. Evidence from drilling logs, magnetotelluric surveys, lost-circulation horizons, downhole temperature surveys, and thermal and chemical properties of surface hot-spring discharge suggests the presence of a large geothermal reservoir north of the towns of Takenoyu and Hagenoyu.
Date: January 22, 1985
Creator: Pritchett, J.W.; Garg, S.K.; Farrell, W.E.; Ishido, T.; Yoshimurs, T.; Murakami, K. et al.
Partner: UNT Libraries Government Documents Department

HYDROGEOLOGY OF THE THERMAL LANDSLIDE

Description: The large Thermal Landslide overlies the initial area of geothermal development at The Geysers. The landslide is waterbearing while the underlying Franciscan formation bedrock units are essentially non-waterbearing except where affected by hydrothermal alteration. Perched ground water moving through the landslide is heated prior to discharge as spring flow.
Date: January 22, 1985
Creator: Vantine, J.
Partner: UNT Libraries Government Documents Department

INITIAL CHEMICAL AND RESERVOIR CONDITIONS AT LOS AZUFRES WELLHEAD POWER PLANT STARTUP

Description: 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 of wellhead and separator pressures, steam and liquid flowrates, steam fraction, enthalpy, and pertinent chemical components. The compilation serves both as a database of conditions during the start-up period and as an initial point to observe changes with continued and increased production. Current plans are to add additional wellhead generators in about two years followed by central power plants when the data have been sufficiently evaluated for optimum plant design. During the next two years, the data acquired at the five 5-MWe wellhead generator units can be compared to this database to observe any significant changes in reservoir behavior at ...
Date: January 22, 1985
Creator: Kruger, P.; Semprini, L.; Verma, S.; Barragan, R.; Molinar, R.; Aragon, A. et al.
Partner: UNT Libraries Government Documents Department

DEVELOPMENT OF THE THERMAL SHALLOW RESERVOIR

Description: The Geysers was discovered in 1847, and its therapeutic mineral baths were widely recognized by 1880. It was not until 1921, however, that the first steam well at The Geysers was drilled. Between 1922 and 1925, eight additional wells were drilled and tested as reported by Allen and Day. Development activity ceased until 1955 when Magma Power Company drilled the first ''commercial'' well. This success led to additional drilling in the Thermal Shallow Reservoir and the commissioning of a 12 MW power plant in September 1960, followed by a 14 MW power plant in February, 1963. This completed the commercial development of the Thermal shallow Reservoir.
Date: January 22, 1985
Creator: Raasch, G.D.
Partner: UNT Libraries Government Documents Department

Breakthrough Time for the Source-Sink Well Doublet

Description: A pressure transient analysis method is presented for interpreting breakthrough time between two constant rate wells. The wells are modeled as two line source wells in an infinite reservoir. The first well injects at a constant rate and the second well produces at a constant rate. We studied the effects of transient pressure conditions on breakthrough time. The first arrival of injected fluid at the production well may be significantly longer under transient condition than under steady state condition. A correlation of the deviation of the breakthrough time for transient pressure conditions from the steady state condition is presented.
Date: January 21, 1986
Creator: Menninger, Will & Sageev, Abraham
Partner: UNT Libraries Government Documents Department

ANALYSIS OF RECHARGE COOLDOWN AT THE WESTERN BOUNDARY OF CERRO PRIETO I GEOTHERMAL FIELD

Description: 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 from the surface to about 700 m over the production zone and a shale-sandstone unit comprising an upper, shallow (alpha) aquifer bounded below by a basement horst overlying a deeper (beta) aquifer. To date, much of the cumulative production at Cerro Prieto I has been from the alpha aquifer. Piezometric level measurements over the first 5 years of operation showed a decline in the western zone beyond the production wells. Over the 10-year period of continuous production, a significant temperature decline has been observed along the westernmost line of wells. Several investigations of the recharge characteristics of the field have ...
Date: January 22, 1985
Creator: Kruger, P.; Lam, S.; Hunsbedt, A.; Esquer, C.; Marquez, R. & Hernandez, L. Cobo, J.
Partner: UNT Libraries Government Documents Department

DISCUSSIONS ON A TYPE OF RESERVOIR CELL BOUNDARY IN THE GEYSERS STEAM FIELD

Description: 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.
Date: January 22, 1985
Creator: Hebein, J.L.
Partner: UNT Libraries Government Documents Department

ON THE CONDITIONS OF WATER AND HEAT FEEDING OF THE PAUZHETKA HYDROTHERMAL SYSTEM (SOUTH KANCHATKA, USSR)

Description: 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 in the Pauzhtka geothermal area, therefore they may be a base for assessment of water and heat feeding of the hydrothermal system. In accordance with these assessments, the main part of water resources is derived from infiltration. Heat feeding may be maintained by cooling of the magma chamber with a volume of 18 km{sup 3} that is in accordance with the volume of Holocene igneous rocks.
Date: January 22, 1985
Creator: Kiryukhin, A.V. & Sugrobov, V.M.
Partner: UNT Libraries Government Documents Department

OPTIMISING FIELD PROVING AND DEVELOPMENT

Description: 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.
Date: January 22, 1985
Creator: Grant, M.A. & Barr,H.
Partner: UNT Libraries Government Documents Department

SVARTSENGI FIELD PRODUCTION DATA AND DEPLETION ANALYSIS

Description: 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 pressure falls with production. While recognizing that no two geothermal fields are alike, we also realize that an understanding of the depletion behavior of Svartsengi, for example, may prove useful in the development of other similar and nearby fields. The main purpose of this paper is to report our depletion analysis of the Svartsengi field using lumped-parameter and water influx modeling: we also report the field's production history.
Date: January 22, 1985
Creator: Gudmundsson, J.S. & Thorhallsson, O.S.
Partner: UNT Libraries Government Documents Department

THE THERMAL 15 RELIEF WELL AND PRODUCTION PERFORMANCE OF THE THERMAL SHALLOW RESERVOIR

Description: Thermal 15 was drilled in November, 1983, to a TD of 700 feet. A steam entry encountered at 490 feet was found to communicate with the high-permeability upflow zone of the Thermal Shallow Reservoir. A low-flow-rate, higher-pressure steam entry at 600 feet was not detected while drilling but was indicated during a subsequent spinner survey. The pressure, flowrate, and enthalpy of the five wells completed in the upflow zone, including the Thermal 4 blowout, were monitored and recorded over a four month period before, during and after Thermal 15 was drilled. It was found that the Thermal 4 blowout communicates with the upflow zone of the Thermal Shallow Reservoir, the Thermal 4 flowrate is controlled by the shallow reservoir pressure, and the high permeability of the upflow zone allows such strong interference effects that three of the four commercial production wells will maximize production from this reservoir. A simple model was developed which describes the pressure-production characteristics of the reservoir over the normal range of operating conditions.
Date: January 22, 1985
Creator: Mogen, P. & Maney, J.
Partner: UNT Libraries Government Documents Department

AN INVESTIGATION OF WELLBORE SCALING AT THE MIRAVALLES GEOTHERMAL FIELD, COSTA RICA

Description: Miravalles geothermal field lies in the Guanacaste province of Costa Rica in Central America. At the time of the study (late 1982), three wells (named PGM-1, PGM-2 and PGM-3), had been drilled and periodically tested in this field during 1980-82. During several of these tests scaling of the wellbore appeared to be a serious problem. This paper presents a portion of a study conducted to define the nature and causes of the scaling problem. No new data were gathered during this study; it was based on the analysis of already existing data as of late 1982. The main limitations in the data as regards this study were: (1) no bottomhole pressure measurements had been made; (2) no temperature or pressure profile under flowing condition was available from any well; (3) a wellhead separator was available at only one well (PGM-1); and (4) although James' lip pressure measurement facilities were available at all wells, in some of the earlier tests (up to May 1981) no measurement of the liquid flow rate was made. The fact that there was scale deposition in the Miravalles wells was indicated by several observations: (1) unusually rapid decline had been experienced in both flow rate and wellhead pressure (p{sub wh}) except when the wells were flowed at a relatively high p{sub wh} level. For example, Figure 1 presents the situation for well PGM-1 during a test (Test 1). This behavior was not due to reservoir depletion because the wells produced a much larger cumulative mass without a serious drop in flow rate or p{sub wh} when flowed above a certain p{sub wh} level, whereas a much smaller cumulative production was possible if a lower p{sub wh} level was maintained. Only a part of the decline in mass flow rate in some of the tests had been ...
Date: January 22, 1985
Creator: Sanyal, S.K.; McNitt, J.R.; Klein, C.W. & Granados, E.E.
Partner: UNT Libraries Government Documents Department

A RESERVOIR ENGINEERING ANALYSIS OF A VAPOR-DOMINATED GEOTHERMAL FIELD

Description: 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.
Date: January 22, 1985
Creator: Dee, J.F. & Brigham, W.E.
Partner: UNT Libraries Government Documents Department

CORRELATIONS BETWEEN VAPOR SATURATION, FLUID COMPOSITION, AND WELL DECLINE IN LARDERELLO

Description: 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.
Date: January 22, 1985
Creator: D'Amore, F. & Pruess, K.
Partner: UNT Libraries Government Documents Department

DECLINE CURVE ANALYSIS FOR INFINITE DOUBLE-POROSITY SYSTEMS WITHOUT WELLBORE SKIN

Description: This paper presents a transient pressure analysis method for analyzing the rate decline of a constant pressure well producing in an infinite double-porosity reservoir, without wellbore skin. This analysis method may be used to interpret well test rate data, and to compute the rate behavior of an infinitely acting reservoir that is being produced at constant pressure. The development of the pseudo steady state log-log type curve Is presented along with a hypothetical example of its use. This type curve allows the estimation of the two controlling parameters in double-porosity systems: {lambda} and {omega}. The first parameter, {lambda}, describes the interporosity flow, and the second parameter, {omega} describes the relative fracture storativity. This paper considers the estimation of these two parameters. The estimations of permeabilities and storativities have been described in the past, hence, are not considered. In a double-porosity system, with pseudo steady state interporosity flow, the initial infinite acting rate decline, representing only the fracture system, is followed by a constant rate flow period. The length of this constant rate flow period is controlled by the parameter {omega}. The beginning of this period is controlled by the interporosity flow parameter, {lambda}. Following this constant rate period, the rate resumes an infinite homogeneous decline, representing the total system, fractures and matrix. The parameters {lambda} and {omega} may be estimated from a log-log match of rate data to the type curve. A comparison between rate responses of two transient flowing matrices and the pseudo steady state matrix Is presented. Transient interporosity flow allows the matrix to increase the well flowrate in the early and transition portions of the flow. The final decline, representing the total system, is identical to the decline with a pseudo steady state matrix.
Date: January 22, 1985
Creator: Sageev, A.; Da Prat, G. & Ramey, H. J., Jr.
Partner: UNT Libraries Government Documents Department

Effects of Water Injection into Fractured Geothermal Reservoirs: A Summary of Experience Worldwide

Description: Reinjection of water into fractured geothermal reservoirs holds potential both for improvement and degradation of total energy recovery. The replacement of reservoir fluid can mean support of placement of reservoir pressures and also more efficient thermal energy recovery, but at the same time the premature invasion of reinjected water back into production wells through high permeability fractures can reduce discharge enthalpy and hence deliverability and useful energy output. Increases in reservoir pressure and maintenance of field output have been observed in operating fields, but unfortunately so too have premature thermal breakthroughs. The design of reinjection schemes, therefore, requires careful investigation into the likely effects, using field experimentation. This paper summarizes field experience with reinjection around the world, with the intention of elucidating characteristics of possible problems. The results summarized in this paper fall into three categories of interest: permeability changes dye to injection (both increases and decreases); the path followed by injected water (as indicated by tracer tests); and the thermal and hydraulic influences of injection on the reinjection well itself and on surrounding producers. [DJE-2005]
Date: June 1, 1982
Creator: Horne, Roland N.
Partner: UNT Libraries Government Documents Department