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Magnetic induction technique for mapping vertical conductive fractures: theory of operation

Description: Utilization of a hot dry rock geothermal resource requires circulation of a fluid (water) through fractures in the rock. The Los Alamos Scientific Laboratory is presently investigating the feasibility and economics of tapping this energy resource. Presently, the fractures in the rock are created by conventional hydraulic fracturing techniques. Accurate determination of the geometry of the fracture system is required so that boreholes may be drilled to complete the circulation system. The theory of a technique designed to map vertical conductive fractures located in resistive rock is presented. The technique is based on magnetic induction. Fracture thickness and strike can be determined from measurements made in a single borehole.
Date: July 1, 1978
Partner: UNT Libraries Government Documents Department

Structural and sedimentological study of the Cerro Prieto geothermal field, Baja California, Mexico

Description: Geophysical and lithologic well logs from over fifty wells have been qualitatively and quantitatively analyzed using both manual and computer interpretation techniques. These logs were studied to make stratigraphic correlations throughout the Cerro Prieto field and to interpret the deltaic depositional environment of the field's lithologic units. Dipmeter and seismic data were of great value in making stratigraphic interpretations and extrapolations. Cross sections were constructed to illustrate lithofacies variations throughout the geothermal field. In turn, these sections were used to construct a three-dimensional model of the Cerro Prieto geothermal reservoir. Petrographic microscopy, scanning electron microscopy, and x-ray diffraction analyses of well-bore cuttings and cores were utilized to determine the degree and distribution of hydrothermal alteration by fluids at temperatures up to 350{sup 0}C, the origins of dissolution porosity, and the relative degree of fracture versus dissolution porosity. The results of these analyses were confirmed by log-derived determinations of formation fluid properties, porosity, and petrophysical properties and by studies of Cerro Prieto cores conducted under in-situ conditions. The results of this research were integrated into the Cerro Prieto reservoir model.
Date: June 1, 1981
Creator: Vonder Haar, S.
Partner: UNT Libraries Government Documents Department

Sandstone consolidation analysis to delineate areas of high-quality reservoirs suitable for production of geopressured geothermal energy along the Texas Gulf Coast

Description: Analysis of reservoir quality of lower Tertiary sandstones along the Texas Gulf Coast delineates areas most favorable for geopressured geothermal exploration. Reservoir quality is determined by whole core, acoustic log, and petrographic analyses. The Wilcox Group has good reservoir potential for geopressured geothermal energy in the Middle Texas Gulf Coast and possibly in adjacent areas, but other Wilcox areas are marginal. The Vicksburg Formation in the Lower Texas Gulf Coast is not prospective. Reservoir quality in the Frio Formation increases from very poor in lowermost Texas, to marginal into the Middle Texas Gulf Coast and to good through the Upper Texas Gulf Coast. The Frio Formation in the Upper Texas Gulf Coast has the best deep-reservoir quality of any unit along the Texas Gulf Coast. (MHR)
Date: January 1, 1979
Creator: Loucks, R.G.; Dodge, M.M. & Galloway, W.E.
Partner: UNT Libraries Government Documents Department

Depositional setting, structural style, and sandstone distribution in three geopressured geothermal areas, Texas Gulf Coast

Description: Three areas in the Texas Gulf Coastal Plain were studied using electric logs and seismic-reflection data to interpret their depositional and structural history and to compare their potential as geopressured-geothermal reservoirs. The Cuero study area, on the lower Wilcox (upper Paleocene) growth-fault trend, is characterized by closely and evenly spaced, subparallel, down-to-the-basin growth faults, relatively small expansion ratios, and minor block rotation. Distributary-channel sandstones in the geopressured lower Wilcox Group of the South Cook fault block appear to be the best geothermal aquifers in the Cuero area. The Blessing study area, on the lower Frio (Oligocene) growth-fault trend, shows wider and more variable fault spacing and much greater expansion ratios and block rotation, particularly during early Frio time. Thick geopressured sandstone aquifers are laterally more extensive in the Blessing area than in the Cuero area. The Pleasant Bayou study area, like the Blessing area, is on the Frio growth-fault trand, and its early structural development was similar rapid movement of widely spaced faults resulted in large expansion ratios and major block rotation. However, a late-stage pattern of salt uplift and withdrawal complicated the structural style. Thick geopressured lower Frio sandstone aquifers are highly permeable and laterally extensive, as in the Blessing area. In all three areas, geopressured aquifers were created where early, rapid movement along down-to-the-basin growth faults juxtaposed shallow-water sands against older shales, probably deposited in slope environments. Major transgressions followed the deposition of reservoir sands and probably also influenced the hydraulic isolation that allowed the build up of abnormal pressures. 26 refs., 49 figs., 8 tabs.
Date: January 1, 1983
Creator: Winker, C.D.; Morton, R.A.; Ewing, T.E. & Garcia, D.D.
Partner: UNT Libraries Government Documents Department

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 reliability of measuring devices and electro-mechanical components to function properly at borehole temperature exceeding 275/sup 0/C and pressures of 69 MPa (10,000 psi).
Date: January 1, 1980
Creator: Dennis, B.R.
Partner: UNT Libraries Government Documents Department

Heat-flow reconnaissance of the Gulf Coastal Plain

Description: Most of the 46 new values of heat flow determined for the Gulf Coastal Plain are in the low to normal range, but heat-flow values averaging 1.8 heat-flow unit (HFU) were obtained in Claiborne, Ouachita, and Union parishes, Louisiana. Moreover, a zone of relatively high heat-flow values and steep thermal gradients (35 to 46/sup 0/C/km) extends from northern Louisiana into southwestern Mississippi. Also near Pensacola, Florida, temperatures of 50/sup 0/C at 1-km depth have been extrapolated from thermal gradients. Future development of low-grade geothermal resources may be warranted in these areas.
Date: April 1, 1982
Creator: Smith, D.L. & Shannon, S.S. Jr.
Partner: UNT Libraries Government Documents Department

Geothermal investigation of the Warm Springs Fault Geothermal System, Salt Lake County, Utah. Report of Investigation No. 140

Description: The Warm Spring Fault geothermal system is located in northern Salt Lake County at the northern limit of the Salt Lake City corporate boundary. The system is immediately west of the Wasatch Mountains at the easternmost edge of the Basin and Range physiographic province within an active seismic zone referred to as the intermountain seismic belt. The thermal springs of the system are located at the western edge of the Salt Lake salient that is intermediate in elevation between the Wasatch Range to the east and the deep valley graben to the west. Displacement from the salient into the graben occurs along two faults. The Warm Springs Fault has a minimum displacement of approximately 180 m (600 ft), and the down thrown block is buried beneath approximately 120 m (400 ft) of valley fill. A second fault referred to as the Hobo Springs Fault lies to the west and has a total displacement of approximately 1220 m (4000 ft). Major thermal springs appear to be located near the intersections of these major normal faults with each other and with relatively minor pre-Basin and Range structures of the salient. Recharge to the system is believed to be from an undefined source area in the Wasatch Range, and the water is heated in the normal geothermal gradient by circulation to depths of 1.5 to 2 km. Data collected at the Warm Springs Fault geothermal system under the DOE/DGE state coupled program is presented for use by individuals interested in the system.
Date: October 1, 1979
Creator: Murphy, P. & Gwynn, J.W.
Partner: UNT Libraries Government Documents Department

Geothermal resource assessment for North Dakota. Final report

Description: Temperatures in four geothermal aquifers, Inyan Kara (Cretaceous), Mission Canyon (Mississippian), Duperow (Devonian), and Red River (Ordovician) are in the range for low and moderate temperature geothermal resources within an area of about 130,000 km/sup 2/ in North Dakota. The accessible resource base is 13,500 x 10/sup 18/ J., which, assuming a recovery factor of 0.001, may represent a greater quantity of recoverable energy than is present in the basin in the form of petroleum. A synthesis of heat flow, thermal conductivity, and stratigraphic data was found to be significantly more accurate in determining formation temperatures than the use of linear temperature gradients derived from bottom hole temperature data. The thermal structure of the Williston Basin is determined by the thermal conductivities of four principal lithologies: Tertiary silts and sands (1.6 W/m/K), Mesozoic shales (1.2 W/m/K), Paleozoic limestones (3.2 W/m/K), and Paleozoic dolomites (3.5 W/m/K). The stratigraphic placement of these lithologies leads to a complex, multicomponent geothermal gradient which precludes use of any single component gradient for accurate determination of subsurface temperatures.
Date: April 1, 1984
Creator: Gosnold, W.D. Jr.
Partner: UNT Libraries Government Documents Department

Hot dry rock geothermal potential of Roosevelt Hot Springs area: review of data and recommendations

Description: The Roosevelt Hot Springs area in west-central Utah possesses several features indicating potential for hot dry rock (HDR) geothermal development. The area is characterized by extensional tectonics and a high regional heat flow of greater than 105 mW/m/sup 2/. The presence of silicic volcanic rocks as young as 0.5 to 0.8 Myr and totaling 14 km/sup 3/ in volume indicates underlying magma reservoirs may be the heat source for the thermal anomaly. Several hot dry wells have been drilled on the periphery of the geothermal field. Information obtained on three of these deep wells shows that they have thermal gradients of 55 to 60/sup 0/C/km and bottom in impermeable Tertiary granitic and Precambrian gneissic units. The Tertiary granite is the preferred HDR reservoir rock because Precambrian gneissic rocks possess a well-developed banded foliation, making fracture control over the reservoir more difficult. Based on a fairly conservative estimate of 160 km/sup 2/ for the thermal anomaly present at Roosevelt Hot Springs, the area designated favorable for HDR geothermal exploration may be on the order of seven times or more than the hydrogeothermal area currently under development.
Date: May 1, 1981
Creator: East, J.
Partner: UNT Libraries Government Documents Department

Resistivity, induced polarization, and self-potential methods in geothermal exploration

Description: An overview of the literature is presented. This is followed by a statement of some elementary electromagnetic theory necessary to establish the MKS system of units and the fundamental physics governing electrical methods of exploration. Next there is presented a reasonably detailed discussion of the electrical properties of earth materials including normal mode of conduction, surface conduction, electrode polarization, membrane polarization, semiconduction, melt conduction, real and complex resistivity, and the origin of self-potentials in geothermal systems. To illustrate how electrical methods are used within the framework of integrated geological, geochemical, and geophysical exploration, the case history of the Monroe-Red Hill hot springs system is presented.
Date: January 1, 1982
Creator: Ward, S.H. & Sill, W.R.
Partner: UNT Libraries Government Documents Department

Borehole temperature survey analysis hot dry rock geothermal reservoir

Description: The Los Alamos Scientific Laboratory (LASL) has been actively investigating the potential for extracting geothermal energy from hot dry rock. A man-made geothermal reservoir has been formed at the Fenton Hill Test Site in northern New Mexico. The 10-MW (thermal) prototype energy extraction circulation loop has been completed and has been continuously operating since January 28 of this year. The performance of the Phase I 1000-h circulation experiment would establish technological assessment of the particular hot dry rock geothermal reservoir. The major parameters of interest include equipment operations, geochemistry, water loss, and reservoir thermal drawdown. Temperature measurements were used extensively as one method to study the man-made geothermal reservoir. The temperature probe is one of the less complex wellbore survey tools that is readily fielded to allow on-line analysis of changing conditions in the hydraulic-fracture system. Several downhole temperature instruments have been designed and fabricated for use in the GT-2/EE-1 wellbores.
Date: January 1, 1978
Creator: Dennis, B.R. & Murphy, H.D.
Partner: UNT Libraries Government Documents Department

Deep subsurface temperature studies in the basins of new Mexico and neighboring geologic areas: precision continuous temperature logging and comparison with other types of logs

Description: For a variety of well environments, continuous temperature logs at different speeds, taken with appropriate equipment and fast-time-response probes, yield temperature data often reproducible to several hudreths of a degree centigrade. Larger differences in reproducibility (several tenths of a degree centigrade) probably result from changes in the wellbore. Temperature-gradient logs are qualitatively correlated to other logs, such as induction-conductivity, gamma-ray, seismic, bulk-density, and lithologic logs. The qualitative correlation with the induction-conductivity log appears best.
Date: April 1, 1981
Creator: Reiter, M.; Mansure, A.J. & Peterson, B.K.
Partner: UNT Libraries Government Documents Department

Results of investigation at the Ahuachapan Geothermal Field, El Salvador

Description: The Ahuachapan Geothermal Field (AGF) is a 95 megawatt geothemal-sourced power-plant operated by the Comision Ejecutiva Hidroelectrica del Rio Lempa (CEL) of El Salvador. During the past decade, as part of an effort to increase in situ thermal reserves in order to realize the full generation capacity of the AGF, extensive surface geophysical coverage has been obtained over the AGF and the prospective Chipilapa area to the east. The geophysical surveys were performed to determine physical property characteristics of the known reservoir and then to search for similar characteristics in the Chipilapa area. A secondary objective was to evaluate the surface recharge area in the highlands to the south of the AGF. The principal surface electrical geophysical methods used during this period were DC resistivity and magnetotellurics. Three available data sets have been reinterpreted using drillhole control to help form geophysical models of the area. The geophysical models are compared with the geologic interpretations.
Date: April 1, 1990
Creator: Fink, J.B. (HydroGeophysics, Tucson, AZ (United States))
Partner: UNT Libraries Government Documents Department

Modeling heat and mass transfer at the Mesa geothermal Anomaly, Imperial Valley, California. Final project report

Description: The geothermal reservoir modeling effort at the University of Colorado is reviewed briefly. Technical accomplishments during the final funding period 1 April 1978 to 30 November 1978 are described. It is concluded that a physically viable mathematical model of an unexploited geothermal system can be constructed in terms of the fault zone controlled charging of the thermally active section of a reservoir.
Date: February 1, 1979
Creator: Kassoy, D.R. & Goyal, K.P.
Partner: UNT Libraries Government Documents Department

Magnetic induction technique for mapping vertical conductive fractures: electronic design

Description: This report is the last in a series that describes the preliminary design of an instrument capable of mapping conductive fractures deep below the surface of the earth. Earlier reports dealt with theoretical analysis, the general status of the instrument development, and materials vendor searches. Here, attention is focused on the electronics design and prototype hardware to perform the mapping task. A phase-sensitive detector is described that has a sensitivity in the tens of nanovolts. Coil-switching circuitry is also described, as well as a downhole data link tailor-made for this particular instrument's needs.
Date: September 1, 1978
Creator: Landt, J.A.; Koelle, A.R.; Trump, M.A. & Nickell, J.D. Jr.
Partner: UNT Libraries Government Documents Department

Study effects of geopressured-geothermal subsurface environment on elastic properties of Texas Gulf Coast sandstones and shales using well logs, core data, and velocity surveys. Final report

Description: Relations between porosity and permeability for the Pleasant Bayou wells were determined from conventional core data. Porosities from the time average equations required compaction correction factors of 1.9 in hydropressured sandstones and 1.0 in geopressured sandstones. Best average prmeabilities in the geopressured zone were found in the primary production interval 14,687 to 14,716 ft (4477 to 4485 m). Average density gradients were 2.106 x 10/sup -3/ and 2.688 x 10/sup -3/ (gm/cm/sup 3/)/100 ft in sandstones and shales respectively. Compressional (P-wave) and shear (S-wave) velocities from the long-spaced sonic log and bulk densities from the formation density log were used to compute in-situ elastic moduli, Poisson's ratio, V/sub p//V/sub s/, and bulk compressibility in two intervals of deep geopressured sandstone and shale in No. 2 Pleasant Bayou. Most computed values of these parameters seem reasonable. Improved accuracy of travel times from the long-spaced sonic log should permit more accurate depth-to-time correlation with seismic data.
Date: May 1, 1980
Creator: Gregory, A.R.
Partner: UNT Libraries Government Documents Department

Radioactive tracers used to characterize geothermal reservoirs

Description: Data obtained from Br/sup 82/ tracer injections with downhole gamma ray monitoring were used to quantify flow fractions entering and leaving the GT-2B and EE-1 reservoirs at various depths. The Br/sup 82/ tracer method also provided data needed to characterize changes in the reservoir volume and flow distribution within fracture system during the recent 281 day sustained heat extraction experiment at the Hot Dry Rock Fenton Hill Site.
Date: January 1, 1981
Creator: Dennis, B.R.; Potter, R. & Kolar, J.
Partner: UNT Libraries Government Documents Department

Downhole electrical detection of hydraulic fractures in GT-2 and EE-1

Description: Electrical geophysical methods including mise a la masse and self-potential (SP) for determination of hydraulic fracture characteristics were used at the hot dry rock geothermal project. Electrical and induction logs indicated that the resistivity contrast between the granite and 200/sup 0/C water at the 2926-m (9600-ft) depth is a factor of 1000 or more. Thus the water in a hydraulic fracture, formed to connect two adjacent deep holes, is a good conductor compared to the confining granite. Mise a la masse-type measurements were made to help determine the characteristics for hydraulic fractures formed in each of the two geothermal holes GT-2 and EE-1. Once a hydraulic fracture has been formed, mise a la masse effects are obtained both with the fracture pressurized above hydrostatic and when depressurized to hydrostatic. This indicates that once the fracture has been created, enough natural propping exists that a conductive zone persists even when the fracture is deflated. A fracture was formed in a 18-m (60-ft) zone immediately below 1957 m (6420 ft) in EE-1. Later a set of SP logs was run in this zone with no pressure, with pressure building, with pressure decreasing, and again with the fracture depressurized. Results show that during times of change of parameters in hydraulically fractured regions in the hole, natural SP logging helps to determine the position of the fracture. However, after a fracture has come to equilibrium with fluid parameters such as temperature, pressure, salinity, and pH, an effect of the fracture may not be evident. Self-potential logs provide an excellent method for locating the bottom of steel casing that has been set in the hole.
Date: July 1, 1977
Creator: Kintzinger, P.R.; West, F.G. & Aamodt, R.L.
Partner: UNT Libraries Government Documents Department

United States Gulf Coast geopressured-geothermal program. Annual report, 1 November 1980-31 October 1981

Description: The following are included: objectives, overview, coordination assistance, compaction measurements on Texas Gulf Coast Sandstones and Shales; US Gulf Coast Geopressured-Geothermal Aquifer simulation, Preliminary Review of Subsidence Insurance Issues, Geopressured-Geothermal Information System, and Study of Log Derived Water Resistivity Values in Geopressured Geothermal Formations. (MHR)
Date: July 1, 1982
Creator: Dorfman, M.H.; Morton, R.A.; Dunlap, H.F.; Frederick, D.O.; Gray, K.E.; Peters, E.J. et al.
Partner: UNT Libraries Government Documents Department

Geological and geophysical study of the origin of the warm springs in Bath County, Virginia. Final report, June 1, 1975--April 30, 1976

Description: The results of heat flow determinations and a reconnaissance dipole electrical resistivity survey in Bath County are described. A geologic map was compiled based on published maps and supported by reconnaissance geologic mapping in areas where published maps were not available. A regional bipole--dipole electrical resistivity survey was made in order to detect the presence of resistivity lows that might be associated with a geothermal system at depth. A single hole was drilled to a depth of approximately 300 m (approx. 1000 feet) to obtain a heat flow value that is representative of the area. The data were used to attempt to arrive at a model that unambiguously explains the origin of the thermal springs.
Date: January 1, 1976
Creator: Costain, J.K.; Keller, G.V. & Crewdson, R.A.
Partner: UNT Libraries Government Documents Department

Impedance camera: a system for determining the spatial variation of electrical conductivity

Description: A data collection and data interpretation method is presented for predicting, from measurements made on the periphery of the core sample, the electrical conductivity distribution within core samples. This method uses an array of electrodes on the periphery to probe through the core sample. Surprisingly accurate detail can be seen in the estimated conductivity distribution. This method has been demonstrated using synthetic examples modeled and analyzed on a computer. Extensions of the procedure may be useful in subsurface geophysical probing and remote probing methods using physical phenomena satisfying Laplace's equation.
Date: January 31, 1978
Creator: Lytle, R.J. & Dines, K.A.
Partner: UNT Libraries Government Documents Department

Hot dry rock heat mining: An advanced geothermal energy technology

Description: The conventional geothermal industry relies on naturally occurring fluids, either liquids or gases to transport the internal heat of the earth to the surface where it is applied to useful purposes, but there are only a relatively few places where these hydrothermal resources exist at temperatures high enough to generate electric power. Over most of the world, the hot rock beneath the surface is relatively dry. Geothermal energy in the form of hot dry rock (HDR) is abundant, widely distributed, and accessible. Energy extraction from HDR promises to be economically competitive and can be accomplished with essentially no adverse environmental effects. The purpose of this paper is to describe the technology which is being developed to gain access to, mine, and utilize the thermal energy existing in HDR. For the last two decades, the Los Alamos National Laboratory has been working to develop techniques for mining HDR energy. Early worked proved that it is feasible to extract thermal energy using drilling and fracturing techniques adapted from the petroleum and geothermal industries. Recently, results have demonstrated that it should be possible to operate HDR plants in a closed-loop mode with minimal water use. Long-term testing is about to begin at the HDR facility operated by Los Alamos at Fenton Hill in the Mountains of northern New Mexico. The goal of this test will be to demonstrate that useful amounts of energy can be produced from HDR on a sustainable basis. Results of this work will form the basis for design, construction, and operation of economic HDR plants in the future. Significant HDR programs are now underway in a number of countries. As the technology matures, HDR should take its place as a clean, economically competitive energy source for the world. 11 refs., 7 figs., 2 tabs.
Date: January 1, 1991
Creator: Duchane, D.V.
Partner: UNT Libraries Government Documents Department