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An investigation of radial tracer flow in naturally fractured reservoirs

Description: 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 thos… more
Date: January 1, 1991
Creator: Jetzabeth, Ramirez-Sabag; Fernando, Samaniego V.; Jesus, Rivera R. & Rodriguez, Fernando
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Simulating a challenging water dominated geothermal system: The Cerro Prieto field, Baja California, Mexico

Description: A three dimensional, multiphase, numerical simulation model of the Cerro Prieto field was developed and used to verify that the present installed capacity (620 MW) can be sustained for 30 years and to evaluate the impact of an 80 MW addition to the installed capacity in the NE-E of the field on the present production areas. Cerro Prieto is the largest known water-dominated geothermal reservoir in the world, with more than 175 wells drilled to date and 17 years of production history. Wells here … more
Date: January 1, 1991
Creator: Antunez, E.U.; Menzies, A.J. & Sanyal, S.K.
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Simulating wellflow of high-nonocondensable-gas geofluids using laboratory measurements on secondary fluids

Description: An experimental simulation of an actual steam-water geothermal well based on field data obtained in New Zealand is carried out in a two-phase flow facility using dichlorotetrafluoroethane, known commercially as refrigerant 114. The simulation of steam-water flow is accomplished by a similarity theory which is achieved by using appropriate dimensionless numbers; namely, the Mach, Froude, and Reynolds numbers at the flashing front. The theory is used to scale the flow properties from that of wate… more
Date: January 1, 1991
Creator: Laoulache, R.N. & Dipippo, R.
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Experimental study of two-phase flow in rough fractures

Description: Two-phase (air-water) flow experiments were conducted in horizontal artificial fractures. The fractures were between glass plates (1 x 0.5 m) artificially roughened by gluing a layer of glass beads of Imm diameter. Three rough fractures were studied: one with the two surfaces in contact, and two without contact. Videotape observations revealed flow structures similar to those observed in two-phase flow in pipes, with structures depending upon the gas and liquid flow rates. The data of flow rate… more
Date: January 1, 1992
Creator: Fourar, M.; Bories, S. & Lenormand, R.
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Laboratory measurement of sorption in porous media

Description: A new apparatus for measuring steam adsorption-desorption isothermally on rock samples has been installed and initial runs made for rock samples from geothermal reservoirs. The amounts adsorbed measured in these experiments are the same order of magnitude as previous experiments.
Date: January 1, 1992
Creator: Harr, M. S.; Pettit, P. & Ramey, J. J., Jr.
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Seventeenth workshop on geothermal reservoir engineering: Proceedings

Description: PREFACE The Seventeenth Workshop on Geothermal Reservoir Engineering was held at Stanford University on January 29-31, 1992. There were one hundred sixteen registered participants which equaled the attendance last year. Participants were from seven foreign countries: Italy, Japan, United Kingdom, France, Belgium, Mexico and New Zealand. Performance of many geothermal fields outside the United States was described in the papers. The Workshop Banquet Speaker was Dr. Raffaele Cataldi. Dr. Cataldi … more
Date: January 31, 1992
Creator: Ramey, Henry J., Jr.; Kruger, Paul; Miller, Frank G.; Horne, Roland N.; Brigham, William E. & Cook, Jean W.
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Interference test analysis at the Takigami geothermal field, JP

Description: 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 we… more
Date: January 28, 1993
Creator: Itol, Ryuichi; Fukuda, Michihiro; Jinno, Kenji & Gotoh, Hiroki
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Results from a discrete fracture network model of a Hot Dry Rock system

Description: The work described represents a move towards better representations of the natural fracture system. The discrete fracture network model used during the study was the NAPSAC code (Grindrod et al, 1992). The goals of the work were to investigate the application of discrete fracture network models to Hot Dry Rock systems, increase the understanding of the basic thermal extraction process and more specifically the understanding of the Rosemanowes Phase 2B system. The aim in applying the work to the… more
Date: January 28, 1993
Creator: Lanyon, G.W.; Batchelor, A.S. & Ledingham, P.
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Significance of Crack Opening Monitoring for Determining the Growth Behavior of Hydrofractures

Description: 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.
Date: January 28, 1993
Creator: Hashida, Toshiyuki; Sato, Kazushi & Takahashi, Hideaki
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A survey of potential geopressured resource areas in California

Description: 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, … more
Date: January 28, 1993
Creator: Sanyal, S. K.; Robertson-Tait, A.; Kraemer, M. & Buening, N.
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An inverse problem solution to the flow of tracers in naturally fractured reservoirs

Description: This paper presents a solution for the inverse problem to the flow of tracers in naturally fractured reservoirs. The models considered include linear flow in vertical fractures, radial flow in horizontal fractures, and cubic block matrix-fracture geometry. The Rosenbrock method for nonlinear regression used in this study, allowed the estimation of up to six parameters for the cubic block matrix fracture geometry. The nonlinear regression for the three cases was carefully tested against syntetic… more
Date: January 20, 1994
Creator: S., Jetzabeth Ramirez; V., Fernando Samaniego; Rodriguez, Fernando & R., Jesus Rivera
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Liquid-phase dispersion during injection into vapor-dominated reservoirs

Description: The behavior of water injection plumes in vapor-dominated reservoirs is examined. Stressing the similarity to water infiltration in heterogeneous soils, we suggest that everpresent heterogeneities in individual fractures and fracture networks will cause a lateral broadening of descending injection plumes. The process of lateral spreading of liquid phase is viewed in analogy to transverse dispersion in miscible displacement. To account for the postulated “phase dispersion” the conventional two-p… more
Date: January 20, 1994
Creator: Pruess, Karsten
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A study of production/injection data from slim holes and large-diameter production wells at the Oguni Geothermal Field, JP

Description: Production and injection data from 11 slim holes and 10 large-diameter wells at the Oguni Geothermal Field, Japan, were examined in an effort to establish relationships (1) between productivity of large-diameter wells and slim holes, (2) between injectivity and productivity indices and (3) between productivity index and borehole diameter. The production data from Oguni boreholes imply that the mass production from large diameter wells may be estimated based on data from slim holes. Test data fr… more
Date: January 20, 1994
Creator: Garg, S. K.; Combs, Jim & Abe, M.
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Interpretation of pre- and post-fracturing well tests in a geothermal reservoir

Description: Pre- and post-fracturing well tests in TG-2 well drilled next to the Matsukawa field are interpreted for evaluating effects of a massive hydraulic fracturing treatment. The interpreted data include multiple-step rate tests, a two-step rate test, and falloff tests. Pressure behaviors of massive hydraulic fracturing are matched by a simulator of dynamic fracture option. Fracture parting pressures can be evaluated from the multiple-step rate test data. The multiple-step rates during the massive hy… more
Date: January 26, 1995
Creator: Arihara, Norio; Fukagawa, Hiroshi; Hyodo, Masami & Abbaszadeh, Maghsood
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Laboratory measurements on reservoir rocks from The Geysers geothermal field

Description: A suite of laboratory measurements have been conducted on Geysers metagraywacke and metashale recovered from a drilled depth of 2599 to 2602 meters in NEGU-17. The tests have been designed to constrain the mechanical and water-storage properties of the matrix material. Various measurements have been made at a variety of pressures and at varying degrees of saturation. Both compressional and shear velocities exhibit relatively little change with effective confining pressure. In all of the samples… more
Date: January 26, 1995
Creator: Boitnott, G.N.
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Locating an Active Fault Zone in Coso Geothermal Field by Analyzing Seismic Guided Waves From Microearthquake Data

Description: Active fault systems usually provide high-permeability channels for hydrothermal outflow in geothermal fields. Locating such fault systems is of a vital importance to plan geothermal production and injection drilling, since an active fault zone often acts as a fracture-extensive low-velocity wave guide to seismic waves. We have located an active fault zone in the Coso geothermal field, California, by identifying and analyzing a fault-zone trapped Rayleigh-type guided wave from microearthquake d… more
Date: January 26, 1995
Creator: Lou, M.; Malin, P. E. & Rial, J. A.
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Study of desorption in a vapor dominated reservoir with fractal geometry

Description: This paper is an attempt to model well decline in a vapor dominated reservoir with fractal geometry. The fractal network of fractures is treated as a continuum with characteristic anomalous diffusion of pressure. A numerical solver is used to obtain the solution of the partial differential equation including adsorption in the fractal storage space. The decline of the reservoir is found to obey the empirical hyperbolic type relation when adsorption is not present. Desorption does not change the … more
Date: January 26, 1995
Creator: Tudor, Monica; Horne, Roland N. & Hewett, Thomas A.
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Interpretation of interference effects in three production wells in the Kawerau geothermal field, New Zealand

Description: Downhole temperature and pressure, mass flow, and enthalpy measurements on three production wells at Kawerau geothermal field are interpretted to illustrate interference effects between these wells. Feed zone locations within the wells, together with geology and chemistry are discussed. Downhole measurements are made in one well while production flow changes are made on another well to monitor pressure transient effects. The interference effects have implications for planning future production … more
Date: January 24, 1996
Creator: Stevens, Lynell & Koorey, Kevin J.
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Interpretation of the return profile of a tracer test in the Thelamork geothermal field, Iceland

Description: 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.… more
Date: January 24, 1996
Creator: Kocabas, I.; Axelsson, G. & Bjornsson, G.
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Laboratory studies of injection into horizonal fractures

Description: Most geothermal reservoirs are extensively fractured and injected fluids usually enter the reservoir formation at distinct feed points. As the cold water passes through the hot rock, it is heated, and may be recovered at production wells for power production. The influence of fractures is two-fold. Firstly, preferential pathways exist along major faults and the general motion of fluids away from injection wells is controlled by the effective permeability structure. Secondly, since fractures can… more
Date: January 24, 1996
Creator: Fitzgerald, Shaun D.; Pruess, Karsten & van Rappard, Diederik M.
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Simple numerical simulation for liquid dominated geothermal reservoir

Description: A numerical model for geothermal reservoir has been developed. The model used is based on an idealized, two-dimensional case, where the porous medium is isotropic, nonhomogeneous, filled with saturated liquid. The fluids are assumed to have constant and temperature dependent viscosity. A Boussinesq approximation and Darcy’s law are used. The model will utilize a simple hypothetical geothermal system, i.e. graben within horsts structure, with three layers of different permeabilities. Vorticity p… more
Date: January 24, 1996
Creator: Wintolo, Djoko; Sutrisno; Sudjatmiko & Sudarman, S.
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Simulating the effects of adsorption and capillary forces in geothermal reservoirs

Description: 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 specific… more
Date: January 24, 1996
Creator: Sta. Maria, Roman B. & Pingol, Alponso S.
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Simulation studies for wells AH-4bis/AH-17 and AH-18, Ahuachapan Geothermal Field

Description: Well AH-4<sub>bis</sub>, at the Ahuachapan Geothermal Field is planned to be drilled on the same pad as the former AH-4. A simulation study was carried out for two casing dameters 13 5/8 and 9 5/8” in order to estimate its production and to know its economic feasibility. The simulation results indcate a high probability of production in the range of 7 Mwe, equivalent to 120 kg/s total mass flow rate, 1250 kJ/kg at 6 bar-a for the new well AH-4<sub>bis</sub>. Well AH- 17 is good producer, during… more
Date: January 24, 1996
Creator: Monterrosa, Manuel Ernesto
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Stimulation of well SN-12 in the Seltjarnarnes low-temperature field in SW-Iceland

Description: Well SN-12 in the Seltjarnarnes low-temperature field in SW-Iceland was drilled to a depth of 2714 m in the fall of 1994. The well appeared to be almost non-productive at the end of drilling. A comprehensive ten day stimulation program was, therefore, initiated. The program involved, firstly, high-pressure wellhead injection and, secondly, high-pressure injection below a packer placed at 1412 m depth. After about twelve hours of wellhead stimulation the pressure dropped suddenly, indicating tha… more
Date: January 24, 1996
Creator: Tulinius, Helga; Axelsson, Gudni; Tomasson, Jens; Kristmannsdottir, Hrefna & Gudmundsson, Asgrimur
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