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Interpretation of interference data from the Klamath Falls, Oregon geothermal resource

Description: Data from a seven week pressure interference test in the Klamath Falls, Oregon geothermal resource have been analyzed. The data indicate that productive wells are fed by a highly permeable fracture network and that the less permeable matrix blocks contribute significantly to the reservoir storage capacity. Detailed analysis of data from two wells is presented. Data from both of the wells yield a reservoir permeability-thickness (kh) of approximately 1.3x10/sup 6/ md-ft and a storativity (phi c/sub t/h) of 6.8x10/sup -3/ ft/psi. The parameters (lambda and ..omega..), which are determined by the distribution of permeability and storativity between the matrix and fractures, vary by more than an order of magnitude. A sensitivity study shows that for these wells, the pressure transients are not very sensitive to the distribution of permeability and storativity between the fractures and matrix blocks. No hydrologic boundaries were detected during the test. This indicates that the fault which supplies hot water to the shallow hydrothermal system does not behave according to the classical model of either a barrier or constant potential boundary.
Date: November 1, 1983
Creator: Benson, S.M.
Partner: UNT Libraries Government Documents Department

Analysis of injection tests in liquid-dominated geothermal reservoirs

Description: The objective was to develop procedures for analyzing nonisothermal injection test data during the early phases of injection. In particular, methods for determining the permeability-thickness of the formation, skin factor of the well and tracking the movement of the thermal front have been developed. The techniques developed for interpreting injection pressure transients are closely akin to conventional groundwater and petroleum techniques for evaluating these parameters. The approach taken was to numerically simulate injection with a variety of temperatures, reservoir parameters and flowrates, in order to determine the characteristic responses due to nonisothermal injection. Two characteristic responses were identified: moving front dominated behavior and composite reservoir behavior. Analysis procedures for calculating the permeability-thickness of the formation and the skin factor of the well have been developed for each of these cases. In order to interpret the composite reservior behavior, a new concept has been developed; that of a ''fluid skin factor'', which accounts for the steady-state pressure buildup due to the region inside the thermal front. Based on this same concept, a procedure for tracking the movement of the thermal front has been established. The results also identify the dangers of not accounting the nonisothermal effects when analyzing injection test data. Both the permeability-thickness and skin factor of the well can be grossly miscalculated if the effects of the cold-region around the well are not taken into consideration. 47 refs., 30 figs., 14 tabs.
Date: December 1, 1984
Creator: Benson, S.M.
Partner: UNT Libraries Government Documents Department

Computerized data acquisition system for production, injection and interference tests

Description: A computer-based system for collecting, processing, and analyzing pressure transient data has been developed. Primary components include downhole pressure sensors, linedrivers, a micro-computer, data storage disk, scanner, frequency counter, digital voltmeter, power supply, graphics plotter, and printer. In-field data processing and analysis greatly aid in handling the large volume of data that are collected during pressure transients tests, particularly the multiwell interference tests that are so important for characterizing and assessing geothermal reservoirs. In-field data processing provides the field engineer, on a real-time basis, with the information needed to make decisions regarding test parameters and duration. The system has been used on numerous occasions and has proved itself to be reliable under the harsh operating conditions that are usually encountered in the field. This paper describes the advantages of using this type of system for collecting data, the components and configuration of the system, and the software programs used to collect and process the data. Finally, two field applications are presented.
Date: June 1, 1986
Creator: Benson, S.M.
Partner: UNT Libraries Government Documents Department

Technology transfer report: feasibility study for the use of geothermal brine in the Ashdod area, Israel

Description: The hydrothermal potential of the Ashdod area, Israel, was evaluated to determine its suitability as the low grade energy source required to operate the Ashdod desalination plant. An estimated 1250 cubic meters per hour of 120/sup 0/C brine would be adequate to supply the hot water necessary for operating the desalination plant. Considerable interest in oil exploration in the Ashdod area resulted in the drilling of six wells into the Jurassic formations by Oil Exploration (Investments) Ltd. (OEL) in 1976-1980. A small amount of oil was found in two wells, Ashdod 2 and 5. The remaining wells were abandoned as ''dry holes''. Evaluation of the drill cuttings, cores, and the electric logs defined two lithologic units of potential interest for hydrothermal exploitation, the Zohar and Shderot Dolomites. Investigation of the hydrothermal potential of the Jurassic formations underlying the Ashdod area has revealed that the aquifer temperatures range between 85 and 92/sup 0/C. The hydrologic parameters are not well defined; however the matrix permeability of the dolomites and limestones is probably between 1 and 10 md. This is insufficient permeability for a large scale pumping operation such as the one required to operate the desalination plant. Therefore, successful utilization of the resource requires the presence of significant fractures and/or connected vugs in the formation. The very low well productivity and formation plugging may indicate that permeability of the fracture zones may easily be impaired, suggesting that the fracture zones are not suitable production intervals. Until a test is conducted on a properly completed well, it is not possible to evaluate the deliverability of wells tapping these aquifers. 14 refs., 8 figs.
Date: August 1, 1984
Creator: Benson, S.M.
Partner: UNT Libraries Government Documents Department

Well Test Data Analysis From a Naturally Fractured Liquid-Dominated Hydrothermal System

Description: Production test data from a moderate-temperature geothermal well in the Basin and Range Province have been analyzed. The well is completed in granitic basement rock. Both the pressure transient and spinner data confirm that fractures provide the major component of the reservoir permeability. The productivity index of the well decreases and the apparent skin factor increases with increasing flow rate. This behavior is attributed to non-Darcy flow in the fractures near the well bore. A mathematical relation between flow rate and drawdown has been established that includes the non-Darcy and Darcy flow components.
Date: October 1, 1982
Creator: Benson, S. M.
Partner: UNT Libraries Government Documents Department

Pressure transient method for front tracking

Description: A pressure transient technique for tracking the advance of cold water fronts during water flooding and goethermal injection operations has been developed. The technique is based on the concept that the steady state pressure buildup in the reservoir region inside the front can be calculated by a fluid skin factor. By analyzing successive pressure falloff tests, the advance of the front in the reservoir can be monitored. The validity of the methods is demonstrated by application to three numerically simulated data sets, a nonisothermal step-rate injection test, a series of pressure falloffs in a multilayered reservoir, and a series of pressure falloff tests in a water flooded oil reservoir.
Date: August 1, 1983
Creator: Benson, S.M. & Bodvarsson, G.S.
Partner: UNT Libraries Government Documents Department

Summary of well-testing activities at Lawrence Berkeley Laboratory, 1975-1983

Description: Well test data collected from various geothermal fields by the geothermal group at Lawrence Berkeley Laboratory are presented. The type of well tests conducted, the instrumentation used and the data collected are described. Experience gained through interpretation of the data has helped identify problems in test procedures and interpretative methods.
Date: August 1, 1983
Creator: Bodvarsson, M.G. & Benson, S.M.
Partner: UNT Libraries Government Documents Department

Analysis of nonisothermal injection and falloff tests in layered reservoirs

Description: The effects of reservoir layering and gravity segregation on nonisothermal injection and falloff tests are investigated. Results show that layering does not affect injection or falloff data if all the layers are permeable and accept fluids from the wellbore. In such cases, the average permeability, skin factor, and distance to the thermal front can be calculated using the techniques developed for homogeneous reservoirs. Special considerations have to be taken for cases where several layers are impermeable or are permeable but do not accept fluids of the well face. In the first case (impermeable layers), knowledge of the total thickness of the permeable layers is required for the existing techniques to be applied successfully. In the second case, the existing techniques cannot be applied, but characteristic responses from injection and falloff test are seen; therefore, this case can be identified easily. 13 refs., 8 figs.
Date: March 1, 1985
Creator: Halfman, S.E. & Benson, S.M.
Partner: UNT Libraries Government Documents Department

New method for evaluating composite reservoir systems

Description: A simple new technique has been developed for evaluating interference test data in radially symmetric composite reservoirs. The technique is based on the realization that systematic variations in the apparent storage coefficient (calculated from semi-log analysis of the late-time data are indicative of a two-mobility (k/..mu..) reservoir. By analyzing variations in the apparent storage coefficient, both the mobility and size of the inner region can be calculated. The technique is particularly useful for evaluating heterogeneous geothermal systems where the intersection of several faults, or hydrothermal alteration has created a high permeability region in the center of the geothermal field. The technique is applied to an extensive interference test in the geothermal reservoir at Klamath Falls, Oregon. 7 refs., 7 figs.
Date: March 1, 1985
Creator: Benson, S.M. & Lai, C.H.
Partner: UNT Libraries Government Documents Department

Well-test data from geothermal reservoirs

Description: Extensive well testing in geothermal resources has been carried out throughout the western United States and in northern Mexico since 1975. Each resource tested and each well test conducted by LBL during the eight-year period are covered in brief. The information, collected from published reports and memoranda, includes test particulars, special instrumentation, data interpretation when available, and plots of actual data. Brief geologic and hydrologic descriptions of the geothermal resources are also presented. The format is such that well test descriptions are grouped, in the order performed, into major sections according to resource, each section containing a short resource description followed by individual test details. Additional information regarding instrumentation is provided. Source documentation is provided throughout to facilitate access to further information and raw data.
Date: September 1, 1982
Creator: Bodvarsson, M.G. & Benson, S.M.
Partner: UNT Libraries Government Documents Department

User's manual for ANALYZE: a variable-rate, multiple-well, least-squares matching routine for well-test analysis

Description: ANALYZE is a history-matching program designed for pressure-transient analysis of well tests in single-phase, fluid-saturated reservoirs. Both interference tests and production tests can be analyzed to yield reservoir transmissivity (kh/..mu..), storativity (phi ch), and hydrologic boundaries. An analytic solution is used to calculate the pressure drawdown/buildup in an idealized reservoir system. A schematic of the basic reservoir/well model assumed by the computational algorithm is shown. The reservoir is assumed to be an isothermal, isotropic, homogeneous, porous medium of constant thickness and infinite areal extent. The production well is modeled as a line source which fully penetrates the reservoir. The flow into the well is radial and uniformly distributed over the height of the well (gravity effects neglected).
Date: July 1, 1981
Creator: McEdwards, D.G. & Benson, S.M.
Partner: UNT Libraries Government Documents Department

Application of an expert system for analysis of geothermal well tests

Description: WES is an expert system designed at Lawrence Berkeley Laboratory for interpreting well test data. The results of WES's analyses of two geothermal well tests are compared to those calculated using traditional methods. WES is well suited for analyzing well tests in geothermal systems because it is robust enough to carry out analyses of data sets that are noisy or incomplete. It also has a broad knowledge base that recognizes most of the hydrogeologic characteristics observed in geothermal systems, such as double- porosity, fractures, and leaky or sealed boundaries. Application of expert systems for analyzing geothermal well tests has several advantages, including: providing clear documentation of the procedures used in the analysis; providing on-site expertise to guide the testing program; providing a greater knowledge base than a single expert may have; and, greatly decreasing the time required for these analyses. Over the next decade expert systems will become an integral part of resource definition and development programs. This paper provides just one example of how expert systems can be used. 25 refs., 16 figs., 3 tabs.
Date: March 1, 1990
Creator: Mensch, A. & Benson, S.M.
Partner: UNT Libraries Government Documents Department

Nonisothermal effects during injection and falloff tests

Description: The results show that to correctly analyze pressure transients governed by a moving thermal front, the values used for the fluid properties must correspond to the temperature of the injected fluid. On the other hand, for pressure falloff tests and for injection tests conducted in a well cooled by previous injection or drilling, the physical properties of the in situ reservoir fluids must be used. It is also shown that the application of conventional isothermal methods for calculating skin values from injection and falloff data will give erroneous results. A new method is presented for calculating skin values from injection and falloff data that accurately corrects for nonisothermal effects. A number of detailed examples are given that illustrate the suggested method of analysis. The technique is applied to the analysis of injection test data from a well located in the East Mesa geothermal field in southern California.
Date: September 1, 1982
Creator: Benson, S.M. & Bodvarsson, G.S.
Partner: UNT Libraries Government Documents Department

Update to modeling soil selenium concentrations in the shallow soil profile at Kesterson Reservoir Merced County, California

Description: A mass balance model was developed to predict concentrations of water-extractable selenium in surface and subsurface soil by extrapolating the trend observed from 6 years of soil monitoring data collected at Kesterson Reservoir. Correlations between observed and calculated concentrations indicate that the major trends and year-to-year variations are well represented with the model. Results from this exercise were then used, under three climatic scenarios, to simulate the evolution of the soluble selenium inventory 25 years into the future. Based on these simulations, we expect that the availability of the soluble selenium inventory has most likely reached peak levels, and is now declining. However, year-to-year climatic variations may influence the rate of decline, and occasionally reverse this prevailing trend.
Date: January 1, 1996
Creator: Wahl, C. & Benson, S. M.
Partner: UNT Libraries Government Documents Department

Capturing and sequestering carbon by enhancing the natural carbon cycle: Prelimary identification of basic science needs and opportunities

Description: This document summarizes proceedings and conclusions of a US DOE workshop. The purpose of the workshop was to identify the underlying research needed to answer the following questions: (1) Can the natural carbon cycle be used to aid in stabilizing or decreasing atmospheric CO{sub 2} and CH{sub 4} by: (a) Increasing carbon capture; (b) Preventing carbon from returning to the atmosphere through intermediate (<100 years) to long-term sequestration (> 100 years)?; and (2) What kind of ecosystem management practices could be used to achieve this? Three working groups were formed to discuss the terrestrial biosphere, oceans, and methane. Basic research needs identified included fundamental understanding of carbon cycling and storage in soils, influence of climate change and anthropogenic emissions on the carbon cycle, and carbon capture and sequestration in oceans. 2 figs., 4 tabs.
Date: July 1, 1997
Creator: Benson, S.M.
Partner: UNT Libraries Government Documents Department

Comparison of three options for geologic sequestration of CO2 - a case study for California

Description: Options for sequestration of CO{sub 2} are best viewed in light of the regional distribution of CO{sub 2} sources and potential sequestration sites. This study examines the distribution of carbon emissions from fossil fuel power plants in California and their proximity to three types of reservoirs that may be suitable for sequestration: (1) active or depleted oil fields, (2) active or depleted gas fields, and (3) brine formations. This paper also presents a preliminary assessment of the feasibility of sequestering CO{sub 2} generated from large fossil-fuel fired power plants in California and discusses the comparative advantages of three different types of reservoirs for this purpose. Based on a volumetric analysis of sequestration capacity and current CO{sub 2} emission rates from oil/gas fired power plants, this analysis suggests that oil reservoirs, gas fields and brine formations can all contribute significantly to sequestration in California. Together they could offer the opportunity to meet both short and long term needs. In the near term, oil and gas reservoirs are the most promising because the trapping structures have already stood the test of time and opportunities for offsetting the cost of sequestration with revenues from enhanced oil and gas production. In the long term, if the trapping mechanisms are adequately understood and deemed adequate, brine formations may provide an even larger capacity for geologic sequestration over much of California.
Date: September 1, 2000
Creator: Benson, S.M.
Partner: UNT Libraries Government Documents Department

Development and use of a high temperature downhole flowmeter for geothermal well logging

Description: The development and use of a high temperature (300/sup 0/C) downhole flowmeter for geothermal well logging are discussed. The availability of the instrument gives the reservoir engineer a powerful tool for formation evaluation and studying wellbore dynamics. The instrument components, their function, and temperature limitations are discussed in detail. Several field examples of spinner log interpretation are also presented.
Date: December 1, 1983
Creator: Solbau, R.D.; Goranson, C.B. & Benson, S.M.
Partner: UNT Libraries Government Documents Department

Simple model for fault-charged hydrothermal systems

Description: A two-dimensional transient model of fault-charged hydrothermal systems has been developed. The model can be used to analyze temperature data from fault-charged hydrothermal systems, estimate the recharge rate from the fault, and determine how long the system has been under natural development. The model can also be used for theoretical studies of the development of fault-controlled hydrothermal systems. The model has been tentatively applied to the low-temperature hydrothermal system at Susanville, California. A resonable match was obtained with the observed temperature data, and a hot water recharge rate of 9 x 10{sup -6} m{sup 3}s/m was calculated.
Date: June 1, 1981
Creator: Bodvarsson, G.S.; Miller, C.W. & Benson, S.M.
Partner: UNT Libraries Government Documents Department

Simple model for fault-charged hydrothermal systems

Description: A two-dimensional transient model of fault-charged hydrothermal systems has been developed. The model can be used to analyze temperature data from fault-charged hydrothermal systems, estimate the recharge rate from the fault, and determine how long the system has been under natural development. The model can also be used for theoretical studies of the development of fault-controlled hydrothermal systems. The model has been tentatively applied to the low-temperature hydrothermal system at Susanville, California. A reasonable match was obtained with the observed temperature data, and a hot water recharge rate of 9 x 10{sup -6} m{sup 3}/s m was calculated.
Date: August 1, 1981
Creator: Bodvarsson, G.S.; Miller, C.W. & Benson, S.M.
Partner: UNT Libraries Government Documents Department

Evaluation of city well 1, Klamath Falls, Oregon

Description: A city-wide geothermal space heating project is currently under development at Klamath Falls, Oregon. The first phase of the project will require two production wells. Geothermally heated water will be used to heat 14 city, county, state, and federal buildings. At peak load the heating system will require approximately 750 gpm of 200{sup 0}F (or greater) geothermal brine. The first production well was spudded on August 29, 1979. During drilling a major lost circulation zone was encountered between 340 and 360 ft depth. At this time the well was cleaned, reamed, cased to 300 ft, and then pump tested. The well was pumped for a total of 15 1/2 hr. A maximum flow rate of 680, with 77 ft of drawdown, was held constant for 7 1/2 hr. Discharge temperature was approximately 218{sup 0}F. Three observation wells were monitored to determine the impact of producing large quantities of brine on the many private geothermal wells already in use for space heating. Preliminary indications are that the water level decline in the area will be small (2 to 3 ft). However, further testing is recommended to determine the effects of reservoir heterogeneity on the water level decline.
Date: April 1, 1980
Creator: Benson, S.M.; Goranson, C.B. & Schroeder, R.C.
Partner: UNT Libraries Government Documents Department

Recently developed well test insrumentation for low-to-moderate temperature hydrothermal reservoirs

Description: The engineering drawings, assembly instructions, and recommended usage for several of the instruments developed for low and moderate temperature (< 150/sup 0/C) hydrothermal well testing are presented. Included are the drawings for: a downhole pressure and temperature instrument, a multi-conductor cablehead, a line driver to be used with the downhole pressure and temperature instrument, and a fluid-level detector.
Date: August 1, 1981
Creator: Solbau, R.; Goranson, C.B. & Benson, S.M.
Partner: UNT Libraries Government Documents Department

Conceptual model of the Klamath Falls, Oregon geothermal area

Description: Over the last 50 years significant amounts of data have been obtained from the Klamath Falls geothermal resource. To date, the complexity of the system has stymied researchers, leading to the development of only very generalized hydrogeologic and geothermal models of the area. Recently, the large quantity of available temperature data have been re-evaluated, revealing new information on subsurface heat flow and locations of faults in the system. These inferences are supported by borehole, geochemical, geophysical, and hydrologic data. Based on re-evaluation of all available data, a detailed conceptual model for the Klamath Falls geothermal resource is proposed.
Date: January 1, 1987
Creator: Prucha, R.H.; Benson, S.M. & Witherspoon, P.A.
Partner: UNT Libraries Government Documents Department

Interpretation of Interference Data from the Klamath Falls, Oregon Geothermal Resource

Description: Data from a seven week pressure interference test in the Klamath Falls, Oregon geothermal resource have been analyzed. The data indicate that productive wells are fed by a highly permeable fracture network and that the less permeable matrix blocks contribute significantly to the reservoir storage capacity. Detailed analysis of data from two wells is presented. Data from both of the wells yield a reservoir permeability-thickness (kh) of approximately 1.3x10{sup 6} md-ft and a storativity of 6.8x10{sup -3} ft/psi. The parameters ({lamda} and {omega}), which are determined by the distribution of permeability and storativity between the matrix and fractures, vary by more than an order of magnitude. A sensitivity study shows that for these wells, the pressure transients are not very sensitive to the distribution of permeability and storativity between the fractures and matrix blocks. No hydrologic boundaries were detected during the test. This indicates that the fault which supplies hot water to the shallow hydrothermal system does not behave according to the cassical model of either a barrier or constant potential boundary.
Date: December 15, 1983
Creator: Benson, S.M.
Partner: UNT Libraries Government Documents Department

A modeling of buoyant gas plume migration

Description: This work is motivated by the growing interest in injecting carbon dioxide into deep geological formations as a means of avoiding its atmospheric emissions and consequent global warming. Ideally, the injected greenhouse gas stays in the injection zone for a geologic time, eventually dissolves in the formation brine and remains trapped by mineralization. However, one of the potential problems associated with the geologic method of sequestration is that naturally present or inadvertently created conduits in the cap rock may result in a gas leakage from primary storage. Even in a supercritical state, the carbon dioxide viscosity and density are lower than those of the formation brine. Buoyancy tends to drive the leaked CO{sub 2} plume upward. Theoretical and experimental studies of buoyancy-driven supercritical CO{sub 2} flow, including estimation of time scales associated with plume evolution and migration, are critical for developing technology, monitoring policy, and regulations for safe carbon dioxide geologic sequestration. In this study, we obtain simple estimates of vertical plume propagation velocity taking into account the density and viscosity contrast between CO{sub 2} and brine. We describe buoyancy-driven countercurrent flow of two immiscible phases by a Buckley-Leverett type model. The model predicts that a plume of supercritical carbon dioxide in a homogeneous water-saturated porous medium does not migrate upward like a bubble in bulk water. Rather, it spreads upward until it reaches a seal or until it becomes immobile. A simple formula requiring no complex numerical calculations describes the velocity of plume propagation. This solution is a simplification of a more comprehensive theory of countercurrent plume migration (Silin et al., 2007). In a layered reservoir, the simplified solution predicts a slower plume front propagation relative to a homogeneous formation with the same harmonic mean permeability. In contrast, the model yields much higher plume propagation estimates in a high-permeability ...
Date: December 1, 2008
Creator: Silin, D.; Patzek, T. & Benson, S.M.
Partner: UNT Libraries Government Documents Department