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Basin amplification of seismic waves in the city of Pahrump, Nevada.

Description: Sedimentary basins can increase the magnitude and extend the duration of seismic shaking. This potential for seismic amplification is investigated for Pahrump Valley, Nevada-California. The Pahrump Valley is located approximately 50 km northwest of Las Vegas and 75 km south of the Nevada Test Site. Gravity data suggest that the city of Pahrump sits atop a narrow, approximately 5 km deep sub-basin within the valley. The seismic amplification, or ''site effect'', was investigated using a combination of in situ velocity modeling and comparison of the waveforms and spectra of weak ground motion recorded in the city of Pahrump, Nevada, and those recorded in the nearby mountains. Resulting spectral ratios indicate seismic amplification factors of 3-6 over the deepest portion of Pahrump Valley. This amplification predominantly occurs at 2-2.5 Hz. Amplification over the deep sub-basin is lower than amplification at the sub-basin edge, location of the John Blume and Associates PAHA seismic station, which recorded many underground nuclear tests at the Nevada Test Site. A comprehensive analysis of basin amplification for the city of Pahrump should include 3-D basin modeling, due to the extreme basement topography of the Pahrump Valley.
Date: July 1, 2005
Creator: Abbott, Robert E.
Partner: UNT Libraries Government Documents Department

Hot dry rock reservoir characterization and modeling. Progress report, October 1, 1978-September 30, 1979. Final report

Description: Resuls of analytical and experimental studies on hydraulic fracturing and on the characterization and modeling of hot dry rock geothermal energy reservoirs are presented. The first four Chapters are concerned with problems of thermal cracking and heat transfer, with fluid flow through large cracks, and with the stable and unstable growth of water-filled cracks under internal pressure and thermal loading. Experiments are reported, which present visually observable hydraulic fractures in transparent materials to demonstrate the interaction between hydraulic fractures and the development of thermal cracks. Seismic detection of hydraulic fractures is discussed, and a method to invert crack-scattering data is presented. Separate abstracts were prepared for each of the six chapters.
Date: February 1, 1980
Creator: Achenbach, J.D.; Bazant, Z.P.; Dundurs, J.; Keer, L.M.; Nemat-Nasser, S.; Mura, T. et al.
Partner: UNT Libraries Government Documents Department

Hydrothermal injection research program. Annual progress report, FY 1984

Description: Studies are described to develop tracers which do not interact with a reservoir and to calculate the mixing of injected fluids and native reservoir fluids. Techniques to calculate the reactions of injected fluids with reservoir rocks are presented. Test results at East Mesa and Raft River Geothermal fields are described and interpretations of field mixing in terms of reservoir characteristics are developed. Supporting laboratory experiments on fracture flow are used to assure that interpretations of field data are based on sound theoretical concepts. A computer code, FRACSL, is described which is used to analyze the fluid mixing data obtained in laboratory and field experiments.
Date: November 1, 1984
Creator: Adams, M.; Capuano, R. G.; Wright, M.; Clemo, T. M.; Hull, L. C.; Miller, J. D. et al.
Partner: UNT Libraries Government Documents Department

CSDP: The seismology of continental thermal regimes: Final report for period April 1, 1986-April 1, 1987

Description: This report describes progress in the study of both wave propagation in complex structures and source mechanism of geothermal seismic events. The following work was accomplished in the past one-year period: (1) interpretation of long-period events observed at Mt. St. Helens and at the Fenton Hill hot-dry-rock experimental site in terms of seismic radiation from a fluid-filled crack; (2) interpretation of teleseismic data collected in and near the Valles caldera in terms of a model with irregular topography, caldera fill, and magma chamber; (3) interpretation of VSP (Vertical Seismic Profiling) data from the Oroville fault zone by ray tracing and polarization calculation for P, SV, and SH waves in heterogeneous and anisotropic media containing aligned fluid-filled and/or dry cracks; and (4) development of a new powerful method for calculating seismic motions in media with irregular topography and interfaces by the superposition of Gaussian Beams.
Date: July 1, 1987
Creator: Aki, K.
Partner: UNT Libraries Government Documents Department

Seismological investigation of crack formation in hydraulic rock fracturing experiments and in natural geothermal environments. Progress report, September 1, 1979-August 31, 1980

Description: Progress is reported in the following research areas: a synthesis of seismic experiments at the Fenton Hill Hot-Dry-Rock System; attenuation of high-frequency shear waves in the lithosphere; a new kinematic source model for deep volcanic tremors; ground motion in the near-field of a fluid-driven crack and its interpretation in the study of shallow volcanic tremor; low-velocity bodies under geothermal areas; and operation of event recorders in Mt. St. Helens and Newberry Peak with preliminary results from them. (MHR)
Date: September 1, 1980
Creator: Aki, K.
Partner: UNT Libraries Government Documents Department

Seismological investigation of crack formation in hydraulic rock fracturing experiments and in natural geothermal environments. Progress report, September 1, 1980-August 31, 1981

Description: Progress is reported on the following: interpretation of seismic data from hydraulic fracturing experiments at the Fenton Hill Hot Dry Rock Geothermal Site, interpretation of 3-D velocity anomalies in the western US with special attention to geothermal areas, theoretical and observational studies of scattering and attenuation of high-frequency seismic waves, theoretical and observational studies of volcanic tremors in relation to magma transport mechanisms, and deployment and maintenance of 9 event-recorders around Mt. St. Helens. Abstracts of papers submitted for publication are included. (MHR)
Date: September 1, 1981
Creator: Aki, K.
Partner: UNT Libraries Government Documents Department

Seismological investigation of crack formation in hydraulic rock fracturing experiments and in natural geothermal environments. Progress report, September 1, 1981-August 31, 1982

Description: Accomplishments during the present reporting period are: high-quality digital data obtained in the crater and the flank of Mt. St. Helens by the deployment of 9 event-recorders; discovery of striking differences in arrival times and amplitudes of seismic events between the crater station and flank stations; successful interpretation of the above observations by a powerful new method of seismogram synthesis called Gaussian Beam Method; evidence obtained at Mt. St. Helens for a close connection between the volcanic tremor and so-called long-period events; further development of our volcanic tremor model by including acoustic vibration in magma; and development of a high-temperature small-diameter borehole seismograph for use in search of a magma reservoir by listening to seismic events due to thermal stress.
Date: September 1, 1982
Creator: Aki, K.
Partner: UNT Libraries Government Documents Department

The seismology of geothermal regimes. Final report

Description: The authors have been developing seismological interpretation theory and methods applicable to complex structures encountered in geothermal areas for a better understanding of the earth`s geothermal regimes. The questions the y have addressed in their research may be summarized as ``What is going on in the earth`s crust under tectonically active regions; what are the structures and processes responsible for such activities as earthquakes and volcanic eruptions; and how can one capture their essence effectively by means of seismological studies?`` First, the authors found clear evidence for localization of scattered seismic energy in the deep magmatic system of the volcano on the island of Reunion in the Indian Ocean. The seismic coda of local earthquakes show concentrated energy in the intrusive zones as late as 30 to 40 seconds after the origin time. This offers a very effective method for defining a zone of strong heterogeneity on a regional scale, complementary to the high resolution study using trapped modes as pursued in the past project. Secondly, the authors identified about 700 long-period events with various frequencies and durations from the data collected during the past 5 years which included three episodes of eruption. They are applying a finite-element method to the simplest event with the longest period and the shortest duration in order to find the location, geometry and physical properties of their source deterministically. The preliminary result described here suggests that their sources may be a horizontally lying magma-filled crack at a shallow depth under the summit area. In addition to the above work on the Reunion data, they have continued the theoretical and observational studies of attenuation and scattering of seismic waves.
Date: April 1, 1997
Creator: Aki, K.
Partner: UNT Libraries Government Documents Department

Geological and petrophysical characterization of the Ferron Sandstone for 3-D simulation of a fluvial-deltaic reservoir. Deliverable 1.4.4: Ferron Sandstone lithofacies and case-study areas, Emery and Sevier Counties, Utah

Description: The types of dominantly sandstone lithofacies that characterize the Cretaceous Ferron Sandstone reservoir types were tentatively identified before the project began. These reservoir types were defined and mapped at the regional scale and are the subject of the detailed, highly focused case studies. The purpose of conducting detailed case-study analysis is to develop a comprehensive, interdisciplinary, and quantitative characterization of fluvial-deltaic reservoirs which will allow realistic inter-well and reservoir-scale modeling to be used for improved oil-field development in actual reservoirs world-wide. The resulting benefits and value may: (1) increase recoverable reserves by identifying untapped compartments created by reservoir heterogeneity, (2) reduce development costs by more efficiently siting infill drilling locations, (3) increase deliverability by exploiting the reservoir along optimal fluid-flow paths, (4) enhance the application of new technologies, such as horizontal drilling, by identifying optimal drilling directions to maximize fluid-flow, and (5) identify reservoir trends for field extension drilling. Various geologic studies of the Ferron Sandstone were reviewed to compile a list of locations and types of lithofacies in the Ferron Sandstone to be examined in greater detail as part of the subsequent case studies. Preliminary regional interpretations were also used to help select the type and location of lithofacies for case studies. Potential case-study sites were delineated during several reconnaissance field trips by the geologic team. Two case-study sites were selected for the project: Ivie Creek and Willow Springs Wash, in the central and southern parts respectively of the project study area. Results are discussed.
Date: January 4, 1996
Creator: Allison, M.L.
Partner: UNT Libraries Government Documents Department

Geological and petrophysical characterization of the Ferron Sandstone for 3-D simulation of a fluvial-deltaic reservoir. Quarterly progress report, January 1, 1997--March 31, 1997

Description: The objective of this project is to develop a comprehensive, interdisciplinary, and quantitative characterization of a fluvial-deltaic reservoir which will allow realistic inter-well and reservoir-scale modeling to be constructed for improved oil-field development in similar reservoirs world-wide. The geological and petrophysical properties of the Cretaceous Ferron Sandstone in east-central Utah will be quantitatively determined. Both new and existing data will be integrated into a three-dimensional representation of spatial variations in porosity, storativity, and tensorial rock permeability at a scale appropriate for inter-well to regional-scale reservoir simulation. Results could improve reservoir management through proper infill and extension drilling strategies, reduction of economic risks, increased recovery from existing oil fields, and more reliable reserve calculations. Transfer of the project results to the petroleum industry is an integral component of the project.
Date: May 1, 1997
Creator: Allison, M.L.
Partner: UNT Libraries Government Documents Department

Geological and petrophysical characterization of the Ferron Sandstone for 3-D simulation of a fluvial-deltaic reservoir. Quarterly progress report, July 1--September 30, 1995

Description: The objective of this project is to develop a comprehensive, interdisciplinary, and quantitative characterization of a fluvial-deltaic reservoir which will allow realistic inter-well and reservoir-scale modeling to be constructed for improved oil-field development in similar reservoirs world-wide. The geological and petrophysical properties of the Cretaceous Ferron Sandstone in east-central Utah will be quantitatively determined. Both new and existing data will be integrated into a three-dimensional representation of spatial variations in porosity, storativity, and tensorial rock permeability at a scale appropriate for inter-well to regional-scale reservoir simulation. Results could improve reservoir management through proper infill and extension drilling strategies, reduction of economic risks, increased recovery from existing oil fields, and more reliable reserve calculations. Transfer of the project results to the petroleum industry is an integral component of the project. Technical progress this quarter is divided into regional stratigraphy, case studies, stochastic modeling and fluid-flow simulation, and technology transfer activities. The regional stratigraphy of the Ferron Sandstone outcrop belt is being described and interpreted. Detailed geological and petrophysical characterization of the primary reservoir lithofacies typically found in a fluvial-dominated deltaic reservoir, is continuing at selected case-study areas. Interpretations of lithofacies, bounding surfaces, and other geologic information are being combined with permeability measurements from closely spaced traverses and from drill-hole cores (existing and two drilled during the quarter). Petrophysical and statistical analyses are being incorporated with the geological characterization to develop a three-dimensional model of the reservoirs through fluid-flow simulation.
Date: October 30, 1995
Creator: Allison, M.L.
Partner: UNT Libraries Government Documents Department

Geological and petrophysical characterization of the Ferron Sandstone for 3-D simulation of a fluvial-deltaic reservoir. Quarterly progress report, October 1, 1997--December 31, 1997

Description: The objective of this project is to develop a comprehensive, interdisciplinary, and quantitative characterization of a fluvial-deltaic reservoir which will allow realistic inter-well and reservoir-scale modeling to be constructed for improved oil-field development in similar reservoirs world-wide. The geological and petrophysical properties of the Cretaceous Ferron Sandstone in east-central Utah will be quantitatively determined. Both new and existing data will be integrated into a three-dimensional representation of spatial variations in porosity, storativity, and tensorial rock permeability at a scale appropriate for inter-well to regional-scale reservoir simulation. Results could improve reservoir management through proper infill and extension drilling strategies, reduction of economic risks, increased recovery from existing oil fields, and more reliable reserve calculations. Transfer of the project results to the petroleum industry is an integral component of the project.
Date: January 1, 1998
Creator: Allison, M.L.
Partner: UNT Libraries Government Documents Department

Geological and petrophysical characterization of the Ferron Sandstone for 3-D simulation of a fluvial-deltaic reservoir. Quarterly report, April 1, 1997--June 30, 1997

Description: The objective of this project is to develop a comprehensive, interdisciplinary, and quantitative characterization of a fluvial-deltaic reservoir which will allow realistic inter-well and reservoir-scale modeling to be constructed for improved oil-field development in similar reservoirs world-wide. The geological and petrophysical properties of the Cretaceous Ferron Sandstone in east-central Utah will be quantitatively determined. Both new and existing data will be integrated into a three-dimensional representation of spatial variations in porosity, storativity, and tensorial rock permeability at a scale appropriate for inter-well to regional-scale reservoir simulation. Results could improve a reservoir management through proper infill and extension drilling strategies, reduction of economic risks, increased recovery from existing oil fields, and more reliable reserve calculations. Transfer of the project results to the petroleum industry is an integral component of the project.
Date: July 1, 1997
Creator: Allison, M.L.
Partner: UNT Libraries Government Documents Department

Geological and petrophysical characterization of the ferron sandstone for 3-D simulation of a fluvial-deltaic reservoir. Quarterly report, January 1 - March 31, 1996

Description: The objective of this project is to develop a comprehensive, interdisciplinary, and quantitative characterization of a fluvial- deltaic reservoir which will allow realistic inter-well and reservoir-scale modeling to be constructed for improved oil-field development in similar reservoirs world-wide. The geological and petrophysical properties of the Cretaceous Ferron Sandstone in east-central Utah will be quantitatively determined. Both new and existing data will be integrated into a three-dimensional representation of spatial variations in porosity, storativity, and tensorial rock permeability at a scale appropriate for inter-well to regional-scale reservoir simulation. Results could improve reservoir management through proper infill and extension drilling strategies, reduction of economic risks, increased recovery from existing oil fields, and more reliable reserve calculations. Technical progress this quarter is divided into case-study evaluation, geostatistics, and technology transfer activities. The work focused on one parasequence set, referred to as the Kf-1, in the Willow Springs Wash and Ivie Creek case-study areas. In the Ivie Creek case-study area the Kf-1 represents a river-dominated delta deposit which changes from proximal to distal from east to west. In the Willow Springs Wash case-study area the Kf-1 contains parasequences which represent river-dominated and wave-modified environments of deposition. Interpretations of lithofacies, bounding surfaces, and other geologic information are being used to determine reservoir architecture. Graphical interpretations of important flow boundaries in the case-study areas, identified on photomosaics, are being used to construct cross sections, paleogeographic, maps, and reservoir models. Geostatistical analyses are being incorporated with the geological characterization to develop a three-dimensional model of the reservoirs for fluid-flow simulation.
Date: April 1, 1996
Creator: Allison, M.L.
Partner: UNT Libraries Government Documents Department

Geological and petrophysical characterization of the Ferron Sandstone for 3-D simulation of a fluvial-deltaic reservoir. Quarterly report, July 1--September 30, 1997

Description: The objective of this project is to develop a comprehensive, interdisciplinary, and quantitative characterization of a fluvial-deltaic reservoir which will allow realistic inter-well and reservoir-scale modeling to be constructed for improved oil-field development in similar reservoirs world-wide. The geological and petrophysical properties of the Cretaceous Ferron Sandstone in east-central Utah will be quantitatively determined. Both new and existing data will be integrated into a three-dimensional representation of spatial variations in porosity, storativity, and tensorial rock permeability at a scale appropriate for inter-well to regional-scale reservoir simulation. Results could improve reservoir management through proper infill and extension drilling strategies, reduction of economic risks, increased recovery from existing oil fields, and more reliable reserve calculations. Two activities continued this quarter as part of the geological and petrophysical characterization of the fluvial-deltaic Ferron Sandstone: (1) evaluation of the Ivie Creek and Willow Springs Wash case-study areas and (2) technology transfer.
Date: November 1, 1997
Creator: Allison, M.L.
Partner: UNT Libraries Government Documents Department

Geological and petrophysical characterization of the Ferron Sandstone for 3-D simulation of a fluvial-deltaic reservoir. Quarterly technical progress report, January 1--March 31, 1997

Description: The objective of this project is to develop a comprehensive, interdisciplinary, and quantitative characterization of a fluvial-deltaic reservoir which will allow realistic inter-well and reservoir-scale modeling to be constructed for improved oil-field development in similar reservoirs world-wide. The geological and petrophysical properties of the Cretaceous Ferron Sandstone in east-central Utah will be quantitatively determined. Both new and existing data will be integrated into a three-dimensional representation of spatial variations in porosity, storativity, and tensorial rock permeability at a scale appropriate for inter-well to regional-scale reservoir simulation. Results could improve reservoir management through proper infill and extension drilling strategies, reduction of economic risks, increased recovery from existing oil fields, and more reliable reserve calculations. Transfer of the project results to the petroleum industry is an integral component of the project.
Date: April 1, 1997
Creator: Allison, M.L.
Partner: UNT Libraries Government Documents Department

Geological and petrophysical characterization of the Ferron Sandstone for 3-D simulation of a fluvial-deltaic resevoir. Quarterly report, October 1, 1996--December 31, 1996

Description: The objective of this project is to develop a comprehensive, interdisciplinary, and quantitative characterization of a fluvial-deltaic reservoir which will allow realistic inter-well and reservoir-scale modeling to be constructed for improved oil-field development in similar reservoirs world-wide. The geological and petrophysical properties of the Cretaceous Ferron Sandstone in east-central Utah will be quantitatively determined. Both new and existing data will be integrated into a three dimensional representation of spatial variations in porosity, storativity, and tensorial rock permeability at a scale appropriate for inter-well to regional-scale reservoir simulation. Results could improve reservoir management through proper infill and extension drilling strategies, reduction of economic risks, increased recovery from existing oil fields, and more reliable reserve calculations. Transfer of the project results to the petroleum industry is an integral component of the project.
Date: March 1, 1997
Creator: Allison, M.L.
Partner: UNT Libraries Government Documents Department

Geothermal regimes of the Clearlake region, northern California

Description: The first commercial production of power from geothermal energy, at The Geysers steamfield in northern California in June 1960, was a triumph for the geothermal exploration industry. Before and since, there has been a search for further sources of commercial geothermal power in The Geysers--Clear Lake geothermal area surrounding The Geysers. As with all exploration programs, these were driven by models. The models in this case were of geothermal regimes, that is, the geometric distribution of temperature and permeability at depth, and estimates of the physical conditions in subsurface fluids. Studies in microseismicity and heat flow, did yield geophysical information relevant to active geothermal systems. Studies in stable-element geochemistry found hiatuses or divides at the Stoney Creek Fault and at the Collayomi Fault. In the region between the two faults, early speculation as to the presence of steamfields was disproved from the geochemical data, and the potential existence of hot-water systems was predicted. Studies in isotope geochemistry found the region was characterized by an isotope mixing trend. The combined geochemical data have negative implications for the existence of extensive hydrothermal systems and imply that fluids of deep origin are confined to small, localized systems adjacent to faults that act as conduits. There are also shallow hot-water aquifers. Outside fault-localized systems and hot-water aquifers, the area is an expanse of impermeable rock. The extraction of energy from the impermeable rock will require the development and application of new methods of reservoir creation and heat extraction such as hot dry rock technology.
Date: June 1, 1998
Creator: Amador, M.; Burns, K.L. & Potter, R.M.
Partner: UNT Libraries Government Documents Department

Improved storage efficiency through geologic modeling and reservoir simulation

Description: The US Department of Energy (DOE), through partnerships with industry, is demonstrating the importance of geologic modeling and reservoir simulation for optimizing the development and operation of gas storage fields. The geologic modeling and reservoir simulation study for the Natural Fuel Gas Supply Corporation CRADA was completed in September 1995. The results of this study were presented at the 1995 Society of Petroleum Engineers` (SPE) Eastern Regional Meeting. Although there has been no field verification of the modeling results, the study has shown the potential advantages and cost savings opportunities of using horizontal wells for storage enhancement. The geologic modeling for the Equitrans` CRADA was completed in September 1995 and was also presented at the 1995 SPE Eastern Regional Meeting. The reservoir modeling of past field performance was completed in November 1996 and prediction runs are currently being made to investigate the potential of offering either a 10 day or 30 day peaking service in addition to the existing 110 day base load service. Initial results have shown that peaking services can be provided through remediation of well damage and by drilling either several new vertical wells or one new horizontal well. The geologic modeling for the Northern Indiana Public Service Company CRADA was completed in November 1996 with a horizontal well being completed in January 1997. Based on well test results, the well will significantly enhance gas deliverability from the field and will allow the utilization of gas from an area of the storage field that was not accessible from their existing vertical wells. Results are presented from these three case studies.
Date: November 1, 1997
Creator: Ammer, J.R.; Mroz, T.H. & Covatch, G.L.
Partner: UNT Libraries Government Documents Department

Geophysical study of the crust and upper mantle beneath the central Rio Grande rift and adjacent Great Plains and Colorado Plateau

Description: As part of the national hot dry rock (HDR) geothermal program conducted by Los Alamos Scientific Laboratory, a regional deep magnetotelluric (MT) survey of Arizona and New Mexico was performed. The main objective of the MT project was to produce a regional geoelectric contour map of the pervasive deep electrical conductor within the crust and/or upper mantle beneath the Colorado Plateau, Basin and Range Province, and Rio Grande rift. Three MT profiles cross the Jemez lineament. Preliminary one-dimensional analysis of the data suggest the lineament is associated with anomalously high electrical conductivity very shallow in the crust. An MT/audiomagnetotelluric (AMT) study of a 161 km/sup 2/ HDR prospect was performed on the Zuni Indian Reservation, New Mexico. Two-dimensional gravity modeling of a 700-km gravity profile at 34/sup 0/30'N latitude was used to study the crust and upper mantle beneath the Rio Grande rift. Several models of each of three consecutive layers were produced using all available geologic and geophysical constraints. Two short-wavelength anomalies along the gravity profile were analyzed using linear optimization techniques.
Date: March 1, 1981
Creator: Ander, M.E.
Partner: UNT Libraries Government Documents Department

Secondary oil recovery from selected Carter sandstone oilfields--Black Warrior Basin, Alabama. Final report

Description: Producibility problems, such as low reservoir pressure and reservoir heterogeneity, have severely limited oil production from the Central Bluff and North Fairview fields. Specific objectives for this project were: To successfully apply detailed geologic and engineering studies with conventional waterflood technologies to these fields in an effort to increase the ultimate economic recovery of oil from Carter sandstone fields; To extensively model, test and evaluate these technologies; thereby, developing a sound methodology for their use and optimization; and To team with Advanced Resources International and the US DOE to assimilate and transfer the information and results gathered from this study to other oil companies to encourage the widespread use of these technologies. At Central Bluff, water injection facilities were constructed and water injection into one well began in January 1993. Oil response from the waterflood has been observed at both producing wells. One of the producing wells has experienced early water breakthrough and a concomitant drop in secondary oil rate. A reservoir modeling study was initiated to help develop an appropriate operating strategy for Central Bluff. For the North Fairview unit waterflood, a previously abandoned well was converted for water injection which began in late June 1993. The reservoir is being re-pressurized, and unit water production has remained nil since flood start indicating the possible formation of an oil bank. A reservoir simulation to characterize the Carter sand at North Fairview was undertaken and the modeling results were used to forecast field performance. The project was terminated due to unfavorable economics. The factors contributing to this decision were premature water breakthrough at Central Bluff, delayed flood response at North Fairview and stalled negotiations at the South Bluff site.
Date: February 1, 1995
Creator: Anderson, J. C.
Partner: UNT Libraries Government Documents Department

Preliminary three-dimensional discrete fracture model, Tiva Canyon tuff, Yucca Mountain area, Nye County, Nevada

Description: A three-dimensional discrete fracture model was completed to investigate the potential effects of fractures on the flow of water at Yucca Mountain, Nye County, Nevada. A fracture network of the Exploratory Studies Facility starter tunnel area was simulated and calibrated with field data. Two modeled volumes were used to simulate three-dimensional fracture networks of the Tiva Canyon tuff. One volume had a width and length of 150 meters, and the other had a width and length of 200 meters; both volumes were 60 meters thick. The analysis shows that the fracture system in the Exploratory Studies Facility starter tunnel area has numerous connected fractures that have relatively large permeabilities. However, pathway analysis between three radial boreholes indicated there were few pathways and little connection, which is consistent with results of cross-boreholes pressure testing. Pathway analysis also showed that at the scales used there was only one pathway connecting one end of the flow box to the opposite end. The usual vertical pathway was along one large fracture, whereas in four horizontal directions the pathway was from multiple fracture connections. As a result, the fracture network can be considered sparse. The fracture network was refined by eliminating nonconductive fractures determined from field-derived permeabilities. Small fractures were truncated from the simulated network without any effect on the overall connectivity. Fractures as long as 1.25 meters were eliminated (a large percentage of the total number of fractures) from the network without altering the number of pathways. Five directional permeabilities were computed for the 150- and 200-meter-scale flow box areas. Permeabilities for the 150-meter scale vary by almost two orders of magnitude, with the principal permeability direction being easterly. At the 200-meter scale, however, the flow box permeabilities only vary by a factor of four, with the principal permeability direction being vertical.
Date: September 1, 1998
Creator: Anna, L. O.
Partner: UNT Libraries Government Documents Department

Preliminary three-dimensional discrete fracture model of the Topopah Spring tuff in the Exploratory Studies Facility, Yucca Mountain area, Nye County, Nevada

Description: Discrete-fracture modeling is part of site characterization for evaluating Yucca Mountain, Nye County, Nevada, as a potential high-level radioactive-waste repository site. Because most of the water and gas flow may be in fractures in low-porosity units, conventional equivalent-continuum models do not adequately represent the flow system. Discrete-fracture modeling offers an alternative to the equivalent-continuum method. This report describes how discrete-fracture networks can be constructed and used to answer concerns about the flow system at Yucca Mountain, including quantifying fracture connectivity, deriving directional-permeability distributions for one-and two-phase flow, determining parameters of anisotropy at different scales, and determining at what scale the rock functions as an equivalent continuum. A three-dimensional discrete-fracture model was developed to investigate the effects of fractures on flow of water and gas in the Topopah Spring tuff of Miocene age in the Exploratory Studies Facility at Yucca Mountain. Fracture data, used as model input, were taken exclusively from detailed line surveys in the Exploratory Studies Facility and converted into input parameters for simulation. A simulated fracture network was calibrated to field data. The simulated discrete fracture network was modified by eliminating nonconductive fractures determined from field-derived permeabilities. Small fractures also were removed from the simulated network without affecting the overall connectivity. Fractures, as much as 1.50 meters in length, were eliminated (a large percentage of the total number of fractures) from the network without altering the number of connected pathways. The analysis indicates that the fracture system in the Exploratory Studies Facility has numerous connected fractures that have relatively large permeabilities, but there are relatively few connected pathways across the simulated region. The fracture network was, therefore, sparse.
Date: September 1, 1998
Creator: Anna, L.O.
Partner: UNT Libraries Government Documents Department

When the hole is dry: the HDR alternative in the cascades

Description: The Hot Dry Rock (HDR) method of heat extraction was developed by Los Alamos in silicic plutonic-metamorphic rocks of Precambrian age. Now that the method and mechanisms are better understood, other rock types are under consideration as potential HDR reservoirs. High heat flow over much of the Northwest indicates the potential for geothermal power and heat is great if ways to develop it could be found. Currently two conceptual models for HDR development in volcanic rocks are under development. Experiments planned for this summer should indicate how the rocks behave and how this behavior compares to existing models.
Date: January 1, 1981
Creator: Arney, B.; Brown, D. & Potter, R.
Partner: UNT Libraries Government Documents Department