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Pressure losses in fracture-dominated reservoirs: the wellbore constriction effect

Description: Improved energy production from many types of energy reservoirs such as hot dry rock geothermal as well as hydraulically fractured oil, gas, and other geothermal reservoirs requires a better understanding of the fluid mechanics in the vicinity of the fracture-wellbore intersection. Typically, the aperture (smallest dimension) of a hydraulic fracture is only of the order of 1 mm (0.04 in.) so that reasonable energy production rates from geothermal systems require fairly large flow velocities wit… more
Date: January 1, 1980
Creator: Murphy, H.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
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A semi-analytical method for heat sweep calculations in fractured reservoirs

Description: An analytical approximation is developed for purely conductive heat transfer from impermeable blocks of rock to fluids sweeping past the rocks in fractures. The method was incorporated into a multi-phase fluid and heat flow simulator. Comparison with exact analytical solutions and with simulations using a multiple interacting continua approach shows very good accuracy, with no increase in computing time compared to porous medium simulations. 14 refs., 3 figs., 5 tabs.
Date: January 1, 1988
Creator: Pruess, K. & Wu, Y.S.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
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Geothermal drilling problems and their impact on cost

Description: Historical data are presented that demonstrate the significance of unexpected problems. In extreme cases, trouble costs are the largest component of well costs or severe troubles can lead to abandonment of a hole. Drilling experiences from US geothermal areas are used to analyze the frequency and severity of various problems. In addition, average trouble costs are estimated based on this analysis and the relationship between trouble and depth is discussed. The most frequent drilling and complet… more
Date: January 1, 1982
Creator: Carson, C. C.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
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Rock Matrix and Fracture Analysis of Flow in Western Tight Gas Sands

Description: Advanced core analysis includes measurements on the matrix properties of the rock. Matrix properties are important even in fractured wells since it is these properties which determine the rate of gas flow into the fractures. Cores are being tested from the fluvial, coastal, and paludal zones of the Mesaverde. At least two cores from each of these zones from all three wells will be analyzed. Properties measured include permeability as a function of confining pressure over the range of 500 to 500… more
Date: January 1, 1985
Creator: Morrow, N. R.; Brower, K. R. & Ward, J. S.
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
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Well test analysis for naturally-fractured reservoirs

Description: In this work pressure transient analysis for constant rate production and transient rate analysis for constant pressure production are presented for a naturally fractured reservoir. Constant producing pressure solutions, which define declining production rates with time, are presented. The solutions for the dimensionless flowrate and pressure are based on a model presented by Warren and Root (1963). The results obtained for a finite no-flow outer boundary are new and surprising. It was found th… more
Date: January 1, 1982
Creator: Da Prat, G. C.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
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Calibration models for fractured igneous rock environments

Description: At the present time, geophysical well logs are not calibrated for igneous and metamorphic lithologies or for fracture porosity. These geologic conditions are routinely encountered in geothermal reservoirs and geothermal fields. Three large calibration models or test pits are presently being fabricated. Each calibration model will be constructed of large stone blocks which have a cored-borehole and wire-sawn simulated fractures. Details of the test pit size, simulated fracture locations, rock ty… more
Date: January 1, 1980
Creator: Mathews, M.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
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Injection into a fractured geothermal reservoir

Description: A detailed study is made on the movement of the thermal fronts in the fracture and in the porous medium when 100{sup 0}C water is injected into a 300{sup 0}C geothermal reservoir with equally spaced horizontal fractures. Numerical modeling calculations were made for a number of thermal conductivity values, as well as different values of the ratio of fracture and rock medium permeabilities. One important result is an indication that although initially, the thermal front in the fracture moves ver… more
Date: May 1, 1980
Creator: Bodvarsson, G. S. & Tsang, C. F.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
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Comparison of pressure ransient response in intensely and sparsely fractured reservoirs

Description: A comprehensive analytical model is presented to study the pressure transient behavior of a naturally fractured reservoir with a continuous matrix block size distribution. Geologically realistic probability density functions of matrix block size are used to represent reservoirs of varying fracture intensity and uniformity. Transient interporosity flow is assumed and interporosity skin is incorporated. Drawdown and interference pressure transient tests are investigated. The results show distinct… more
Date: January 1, 1989
Creator: Johns, R. T.
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
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Thermal depletion of a geothermal reservoir with both fracture and pore permeability

Description: A method for estimating the useful lifetime of a reservoir in porous rock where the injection and production wells intersect a fracture system is presented. Equations were derived for the pore-fluid and fracture-fluid temperatures averaged over large regions of the geothermal field. Problems such as incomplete areal sweep and interfingering of cool and hot fluids are ignored. Approximate equations relating average temperatures to the heat flowing from rock to fluid were developed, and their use… more
Date: August 10, 1976
Creator: Kasameyer, P.W. & Schroeder, R.C.
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
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Stanford Geothermal Program, reservoir and injection technology

Description: This annual report of the Stanford Geothermal Program presents major projects in reservoir and injection technology. The four include: (1) an application of the boundary element method to front tracking and pressure transient testing; (2) determination of fracture aperture, a multi-tracer approach; (3) an analysis of tracer and thermal transients during reinjection; and, (4) pressure transient modeling of a non-uniformly fractured reservoir. (BN)
Date: December 1, 1988
Creator: Horne, R.; Ramey, H.J. Jr.; Miller, F.G.; Brigham, W.E. & Kruger, P.
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
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Pressure oscillations caused by momentum on shut in of a high rate well in a fractured formation

Description: Pressure transient testing techniques are an important part of reservoir and production testing procedures. These techniques are frequently used to determine practical information about underground reservoirs such as the permeability, porosity, liquid content, reservoir and liquid discontinuities and other related data. This information is valuable in helping to analyze, improve and forecast reservoir performance. This report is concerned with developing models for pressure transient well testi… more
Date: June 1, 1989
Creator: Bhatnagar, S.
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
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Hot Dry Rock Geothermal Energy Development Program. Annual report, fiscal year 1979

Description: The Fenton Hill Project is still the principal center for developing methods, equipment, and instrumentation for creating and utilizing HDR geothermal reservoirs. The search for a second site for a similar experimental system in a different geological environment has been intensified, as have the identification and characterization of other HDR areas that may prove suitable for either experimental or commercial development. The Phase I fracture system was enlarged during FY79. Drilling of the i… more
Date: August 1, 1980
Creator: Cremer, G. M.; Duffield, R. B.; Smith, M. C. & Wilson, M. G.
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
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Reservoir and injection technology and Heat Extraction Project

Description: For the Stanford Geothermal Program in the fiscal year 1989, the task areas include predictive modeling of reservoir behavior and tracer test interpretation and testing. Major emphasis is in reservoir technology, reinjection technology, and heat extraction. Predictive modeling of reservoir behavior consists of a multi-pronged approach to well test analysis under a variety of conditions. The efforts have been directed to designing and analyzing well tests in (1) naturally fractured reservoirs; (… more
Date: December 31, 1989
Creator: Horne, R.N.; Ramey, H.H. Jr.; Miller, F.G.; Brigham, W.E. & Kruger, P.
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
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Modeling Wettability Alteration using Chemical EOR Processes in Naturally Fractured Reservoirs

Description: The objective of our search is to develop a mechanistic simulation tool by adapting UTCHEM to model the wettability alteration in both conventional and naturally fractured reservoirs. This will be a unique simulator that can model surfactant floods in naturally fractured reservoir with coupling of wettability effects on relative permeabilities, capillary pressure, and capillary desaturation curves. The capability of wettability alteration will help us and others to better understand and predict… more
Date: September 30, 2007
Creator: Delshad, Mojdeh; Pope, Gary A. & Sepehrnoori, Kamy
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
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Numerical modeling of water injection into vapor-dominatedgeothermal reservoirs

Description: Water injection has been recognized as a powerful techniquefor enhancing energy recovery from vapor-dominated geothermal systemssuch as The Geysers. In addition to increasing reservoir pressures,production well flow rates, and long-term sustainability of steamproduction, injection has also been shown to reduce concentrations ofnon-condensible gases (NCGs) in produced steam. The latter effectimproves energy conversion efficiency and reduces corrosion problems inwellbores and surface lines.This r… more
Date: November 6, 2006
Creator: Pruess, Karsten
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
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Borehole survey instrumentation development for geothermal applications

Description: The creation and subsequent study of hot dry rock geothermal reservoirs requires sophisticated tools and instruments that can function for relatively long periods of time in the hostile downhole environment. Detection of fracture dimensions and orientation of the geothermal reservoir is critical for the successful completion of the hot dry rock energy extraction system. The development of downhole instrumentation capable of characterizing the hydraulic-fracture systems must emphasize reliabilit… more
Date: January 1, 1980
Creator: Dennis, B.R.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
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Calibration models for fractured rock environments

Description: Accurate measurement and recording of log data is necessary for effective well evaluation, reservoir engineering assessment, and subsurface geological or geophysical appraisal. Proper interpretation of log data provides accurate subsurface geologic parameters. Calibration data that is auxiliary to the log data will show the degree of log accuracy and indicate the reliability of the estimated subsurface geologic parameters when the log data is reviewed with a knowedge of the calibration procedur… more
Date: January 1, 1980
Creator: Mathews, M.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
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Analysis of tracer and thermal transients during reinjection

Description: This work studied tracer and thermal transients during reinjection in geothermal reserviors and developed a new technique which combines the results from interwell tracer tests and thermal injection-backflow tests to estimate the thermal breakthrough times. Tracer tests are essential to determine the degree of connectivity between the injection wells and the producing wells. To analyze the tracer return profiles quantitatively, we employed three mathematical models namely, the convection-disper… more
Date: October 1, 1989
Creator: Kocabas, I.
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
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Models of natural fracture connectivity: Implication for reservoir permeability

Description: We have investigated common mechanisms responsible for fracture connectivity (or lack thereof) for single and multiple sets of fractures. The methods of study were based on detailed field mapping of fractures in layered sedimentary rocks, typical of producing oil and gas reservoirs and on numerical modeling of the concepts developed from the field observations. The crucial mechanisms important for connectivity have been deduced to be fracture propagation across layer interfaces with or without … more
Date: March 1, 1992
Creator: Aydin, A.
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
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Geothermal drilling and completion research and development program

Description: Current activities include development of high temperature drilling fluids, methods for plugging lost circulation zones, advanced rock cutting techniques, and borehole instrumentation. Three specific projects which are being pursued include: a method for locating fractures which do not intersect the wellbore, a laboratory for simulating lost circulation zones - to be used for development of new materials and techniques, and the understanding of the capabilities and limitations of polycrystallin… more
Date: December 1, 1983
Creator: Kelsey, J. R. & Allen, A. D.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
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Aligned vertical fractures, HTI reservoir symmetry, and Thomsenseismic anisotropy parameters for polar media

Description: Sayers and Kachanov (1991) defined crack-influence parameters that are shown to be directly related to Thomsen (1986) weak-anisotropy seismic parameters for fractured reservoirs when the crack/fracture density is small enough. These results are then applied to the problem of seismic wave propagation in polar (i.e., non-isotropic) reservoirs having HTI seismic wave symmetry due to the presence of aligned vertical fractures and resulting in azimuthal seismic wave symmetry at the earth's surface. … more
Date: December 12, 2007
Creator: Berryman, James G.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
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Drill Pipe Corrosion Control Using an Inert Drilling Fluid

Description: The results of a geothermal drill pipe corrosion field test are presented. When a low-density drilling fluid was required for drilling a geothermal well because of an underpressured, fractured formation, two drilling fluids were alternately used to compare drill pipe corrosion rates. The first fluid was an air-water mist with corrosion control chemicals. The other fluid was a nitrogen-water mist without added chemicals. The test was conducted during November 1980 at the Baca location in norther… more
Date: January 1, 1981
Creator: Caskey, B. C. & Copass, K. S.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
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Multi-Attribute Seismic/Rock Physics Approach to Characterizing Fractured Reservoirs

Description: Most current seismic methods to seismically characterize fractures in tight reservoirs depend on a few anisotropic wave propagation signatures that can arise from aligned fractures. While seismic anisotropy can be a powerful fracture diagnostic, a number of situations can lessen its usefulness or introduce interpretation ambiguities. Fortunately, laboratory and theoretical work in rock physics indicates that a much broader spectrum of fracture seismic signatures can occur, including a decrease … more
Date: November 30, 2004
Creator: Mavko, Gary
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
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Aligned vertical fractures, HTI reservoir symmetry, and Thomsenseismic anisotropy parameters

Description: The Sayers and Kachanov (1991) crack-influence parametersare shown to be directly related to Thomsen (1986) weak-anisotropyseismic parameters for fractured reservoirs when the crack density issmall enough. These results are then applied to seismic wave propagationin reservoirs having HTI symmetry due to aligned vertical fractures. Theapproach suggests a method of inverting for fracture density from wavespeed data.
Date: June 27, 2007
Creator: Berryman, James G.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
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