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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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Mathematical modeling of the behavior of geothermal systems under exploitation

Description: Analytical and numerical methods have been used in this investigation to model the behavior of geothermal systems under exploitation. The work is divided into three parts: (1) development of a numerical code, (2) theoretical studies of geothermal systems, and (3) field applications. A new single-phase three-dimensional simulator, capable of solving heat and mass flow problems in a saturated, heterogeneous porous or fractured medium has been developed. The simulator uses the integrated finite di… more
Date: January 1, 1982
Creator: Bodvarsson, G.S.
Item Type: Refine your search to only Report
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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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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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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Energy extraction operations: some preliminary results

Description: An experimental project being conducted by the Los Alamos Scientific Laboratory (LASL) has extracted thermal energy from Precambrian granitic rock by injection and circulating water through fractured zones or reservoirs. Two boreholes were drilled to depths of about 3 km (10,000 ft) in a location selected for high heat flow and an apparent lack of faulting. Bottom-hole temperature was 205/sup 0/C (400/sup 0/F). The holes were connected at depth by hydraulic fracturing to form a flow path and he… more
Date: January 1, 1979
Creator: Hendron, R.H.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
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Dual permeability modeling of flow in a fractured geothermal reservoir

Description: A three dimensional fracture system synthesis and flow simulation has been developed to correlate drawdown characteristics measured in a geothermal well and to provide the basis for an analysis of tracer tests. A new dual permeability approach was developed which incorporates simulations at two levels to better represent a discrete fracture system within computer limitations. The first incorporates a discrete simulation of the largest fractures in the system plus distributed or representative e… more
Date: January 1, 1986
Creator: Miller, J. D. & Allman, D. W.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
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Summary of hot dry rock geothermal reservoir testing 1978 to 1980

Description: Experimental results and re-evaluation of the Phase I Hot Dry Rock Geothermal Energy reservoirs at the Fenton Hill field site are summarized. Reservoir growth is traced. Reservoir growth was caused not only by pressurization and hydraulic fracturing, but also by heat extraction and thermal contraction effects. Reservoir heat-transfer area grew from 8000 to 50,000 m/sup 2/ and reservoir fracture volume grew from 11 to 266/sup 3/m. Despite this reservoir growth, the water loss rate increased only… more
Date: January 1, 1981
Creator: Dash, Z.V. & Murphy, H.D. (eds.)
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
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Modeling studies of cold water injection into fluid-depleted, vapor-dominated geothermal reservoirs

Description: The physical processes involved in cold water injection into a ''superheated'' fractured reservoir are not yet fully understood, and this insufficient knowledge of the fundamental mechanisms limits the possibility of forecasting future resevoir behavior and optimizing the heat extraction process. Numerical simulation can be a very effective tool in the study of the complex phenomena involved, allowing a rapid examination of different situations and conditions, a systematic investigation of the … more
Date: January 1, 1986
Creator: Calore, C.; Pruess, K. & Celati, R.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
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Representative element modeling of fracture systems based on stochastic analysis

Description: An important task associated with reservoir simulation is the development of a technique to model a large number of fractures with a single description. Representative elements must be developed before reservoir scale simulations can adequately address the effects of intersecting fracture systems on fluid migration. An effective element model will sharply reduce the cost and complexity of large scale simulations to bring these to manageable levels. Stochastic analysis is a powerful tool which c… more
Date: January 1, 1986
Creator: Clemo, T.M.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
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Fractured geothermal reservoir growth induced by heat extraction

Description: Field testing of a hydraulically-stimulated, hot dry rock geothermal system at the Fenton Hill site in northern New Mexico has indicated that significant reservoir growth occurred as energy was extracted. Tracer, microseismic, and geochemical measurements provided the primary quantitative evidence for documenting the increases in accessible reservoir volume and fractured rock surface area that were observed during energy extraction operations which caused substantial thermal drawdown in portion… more
Date: January 1, 1986
Creator: Tester, J. W.; Murphy, H. D.; Grigsby, C. O.; Robinson, B. A. & Potter, R. M.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
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Simulator for unconventional gas resources multi-dimensional model SUGAR-MD. Volume I. Reservoir model analysis and validation

Description: The Department of Energy, Morgantown Energy Technology Center, has been supporting the development of flow models for Devonian shale gas reservoirs. The broad objectives of this modeling program are: (1) To develop and validate a mathematical model which describes gas flow through Devonian shales. (2) To determine the sensitive parameters that affect deliverability and recovery of gas from Devonian shales. (3) To recommend laboratory and field measurements for determination of those parameters … more
Date: January 1, 1982
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
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Reservoir technology research at the Idaho National Engineering Laboratory

Description: The Idaho National Engineering Laboratory (INEL) has been conducting geothermal reservoir research and testing sponsored by the US Department of Energy (DOE) since 1983. The INEL research program is primarily aimed at the development of reservoir engineering techniques for fractured geothermal reservoirs. Numerical methods have been developed which allow the simulation of fluid flow and heat transfer in complex fractured reservoirs. Sensitivity studies have illustrated the importance of incorpo… more
Date: January 1, 1987
Creator: Stiger, S. G. & Renner, J. L.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
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Interwell tracer analyses of a hydraulically fractured granitic geothermal reservoir

Description: Field experiments using fluorescent dye and radioactive tracers (Br{sup 82} and I{sup 131}) have been employed to characterize a hot, low-matrix permeability, hydraulically-fractured granitic reservoir at depths of 2440 to 2960 m (8000 to 9700 ft). Tracer profiles and residence time distributions have been used to delineate changes in the fracture system, particularly in diagnosing pathological flow patterns and in identifying new injection and production zones. The effectiveness of one- and tw… more
Date: January 1, 1979
Creator: Tester, J. W.; Potter, R. M. & Bivins, R. L.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
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Two-phase flow visualization and relative permeability measurement in transparent replicas of rough-walled rock fractures

Description: Understanding and quantifying multi-phase flow in fractures is important for mathematical and numerical simulation of geothermal reservoirs, nuclear waste repositories, and petroleum reservoirs. While the cubic law for single-phase flow has been well established for parallel-plate fractures theoretically and experimentally, no reliable measurements of multi-phase flow in fractures have been reported. This work reports the design and fabrication of an apparatus for visualization of two-phase flo… more
Date: January 1, 1991
Creator: Persoff, P.; Pruess, K. & Myer, L.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
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Flow rate decline of steam wells in fractured geothermal reservoirs

Description: Decline curves are commonly used at The Geysers geothermal field to assess the generating capacity of a producing lease. It is generally assumed that wells will initially be drilled using 40-acre (400 m) spacing, with infill drilling used later to provide additional producing wells as needed. It is commonly believed that the final well spacing should not be less than 10 acres (200 m). Decline curves are used with this approach to estimate the number of make-up wells during a project lifetime (u… more
Date: January 1, 1985
Creator: Bodvarsson, G.S. & Witherspoon, P.A.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
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New model for well test analysis in a purely fractured medium

Description: In a porous medium the flow conduits are small and a large number of conduits are connected to the well. For this reason the medium appears to behave like a continuum on the scale of the well test, and volumetric averaging and continuum approximations are justified. On the contrary, in a fractured medium, only a small number of fractures may intersect the pumping well. These particular fractures will be stressed by a large gradient under well test conditions. Consequently, the early time behavi… more
Date: January 1, 1985
Creator: Karasaki, K.; Long, J.C.S. & Witherspoon, P.A.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
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Geothermal drilling - problems and solutions

Description: Geothermal wells represent approximately 50% of the cost of generating electricity from geothermal resources; typical wells cost $2 M to $3 M. Some of the problems which lead to these high costs are described here and some of the solutions which are being studied by the geothermal industry and the national laboratory research programs. Specific discussions of drilling fluids, advanced drilling methods, and downhole diagnostic hardware are presented.
Date: January 1, 1983
Creator: Kelsey, J.R.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
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