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Active Seismics to Determine Reservoir Characteristics of a Hot Dry Rock Geothermal System
Since 1981 three wells have been drilled to depths of between 2.0 and 2.6 km in the Carnmenellis granite, Cornwall, England in order to create a HDR geothermal system. These wells are separated by between 150 and 300 m and have been hydraulically connected by massive injections of both water and viscous gel (50 cpoise). Passive microseismic monitoring of the hydraulic stimulation and circulation experiments has been used since 1982 to determine the size and structure of the reservoir, and monitor its growth. The active seismic survey techniques of cross-hole seismics and vertical seismic profiling (VSP) have been introduced to complement the passive microseismic monitoring in characterizing the reservoir. The cross-hole seismic surveys indicate that the microseismicity defines the area of joint dilation. The attenuation of high frequencies in the region of microseismicity suggests that the reservoir is composed of a complex zone of cracks rather than a single large fracture. VSP surveys also show a good agreement between the microseismically defined reservoir and seismic signal attenuation. Recent improvements in hardware, computer processing and interpretation indicate that active seismics will play an increasingly important part in mapping and understanding geothermal reservoirs. 11 figs., 10 refs.
Date:
January 20, 1987
Creator:
Green, A.S.P. & Baria, R.
Object Type:
Article
System:
The UNT Digital Library
Altus Times (Altus, Okla.), Vol. 65, No. 17, Ed. 1 Tuesday, January 20, 1987
Daily newspaper from Altus, Oklahoma that includes local, state, and national news along with advertising.
Date:
January 20, 1987
Creator:
unknown
Object Type:
Newspaper
System:
The Gateway to Oklahoma History
Analysis of Injection-Backflow Tracer Tests in Fractured Geothermal Reservoirs
Tracer tests have been an important technique for determining the flow and reservoir characteristics in various rock matrix systems. While the interwell tracer tests are aimed at the characterization of the regions between the wells, single-well injection-backflow tracer tests may be useful tools of preliminary evaluation, before implementing long term interwell tracer tests. This work is concerned with the quantitative evaluation of the tracer return profiles obtained from single well injection-backflow tracer tests. First, two mathematical models of tracer transport through fractures, have been reviewed. These two models are based on two different principles: Taylor Dispersion along the fracture and simultaneous diffusion in and out of the adjacent matrix. Then the governing equations for the transport during the injection-backflow tests have been solved. Finally the results were applied to field data obtained from Raft River and East Mesa geothermal fields. In order to determine the values of the parameters of the models that define the transport mechanisms through fractures a non-linear optimization technique was employed. 26 refs., 10 figs.
Date:
January 20, 1987
Creator:
Kocabas, I. & Horne, R.N.
Object Type:
Article
System:
The UNT Digital Library
Analysis of Thermally Induced Permeability Enhancement in Geothermal Injection Wells
Reinjection of spent geothermal brine is a common means of disposing of geothermal effluents and maintaining reservoir pressures. Contrary to the predictions of two-fluid models (two-viscosity) of nonisothermal injection, an increase of injectivity, with continued injection, is often observed. Injectivity enhancement and thermally-affected pressure transients are particularly apparent in short-term injection tests at the Los Azufres Geothermal Field, Mexico. During an injection test, it is not uncommon to observe that after an initial pressure increase, the pressure decreases with time. As this typically occurs far below the pressure at which hydraulic fracturing is expected, some other mechanism for increasing the near-bore permeability must explain the observed behavior. This paper focuses on calculating the magnitude of the near-bore permeability changes observed in several nonisothermal injection tests conducted at the Los Azufres Geothermal Field. In order to evaluate the pressure transient data and calculate the magnitude of the thermally induced permeability changes, a new analytic solution for calculating pressure transients with time-varying sandface flowrates and temperatures has been developed. The effects of temperature-dependent fluid and rock properties, as well as a moving thermal front, are explicitly included in the calculations. Based on this new solution, a technique is developed for calculating the …
Date:
January 20, 1987
Creator:
Benson, S. M.; Daggett, J. S.; Iglesias, E.; Arellano, V. & Ortiz-Ramirez, J.
Object Type:
Article
System:
The UNT Digital Library
Analysis of Transient Pressure Tests for Olkaria Exploration Wells
Analysis of transient pressure tests for Olkaria West wells shows that both infinite acting and double porosity models can be used to analyze the well behaviour and infer reservoir properties from fall-off steps of long enough duration, in wells where no significant thermal recovery occurs. The double porosity model gives better estimates of reservoir properties than the infinite acting model, for long fall-off steps in wells intercepting fractures. Semilog methods give fairly good estimates of reservoir transmissivity for the long fall-off steps but are highly inaccurate when used independently, especially for the short fall-off steps conducted in most of the wells. Double porosity models can also be used for recovery test analyses where two phase transients are not significant. 6 refs., 11 figs., 8 tabs.
Date:
January 20, 1987
Creator:
Haukwa, Charles B.
Object Type:
Article
System:
The UNT Digital Library
Applying Flowrate Type Curves to Geysers Steam Wells
Dimensionless flowrate type curves were applied to steam wells at The Geysers in an attempt to quantify reservoir properties and to predict flowrate decline. Although data scatter was a problem, the flowrate data was smoothed by a normalization routine based on the back-pressure equation and the wells were modeled by dimensionless functions for a radial system with a infinite or finite outer boundary and a constant pressure inner boundary (composite analytical-empirical type curve). The “match” resulted in a unique D{sub i} value for use in Arps’ equation and a permeability-thickness product (kh) comparable to kh values obtained from pressure buildup analysis. Finally, it was shown that at least four years of data is required to obtain a unique b value. 2 tabs., 12 refs., 12 figs.
Date:
January 20, 1987
Creator:
Enedy, Steve
Object Type:
Article
System:
The UNT Digital Library
The Baytown Sun (Baytown, Tex.), Vol. 65, No. 68, Ed. 1 Tuesday, January 20, 1987
Daily newspaper from Baytown, Texas that includes local, state, and national news along with advertising.
Date:
January 20, 1987
Creator:
Brown, Leon
Object Type:
Newspaper
System:
The Portal to Texas History
Bleeding Characteristics of Geothermal Wells
Abstract: Discharging small flows (order of 1 t/h) from wells is known as bleeding and is to relieve the build-up of gas pressure at the wellhead and to arrest corrosion in the bore. First tests over a range of bleeding flows indicate it as a fruitful subject for study in that temperature and pressure measurements at the wellhead can indicate the well enthalpy and the non-condensible gas content of the production system. Because of environmental restrictions on testing with large discharges in the future, bleeding may soon be the only valid alternative for proving a well’s potential.
Date:
January 20, 1987
Creator:
James, Russell & Gould, Tom
Object Type:
Article
System:
The UNT Digital Library
Cerro Prieto Contents of the Technical Information Files Generated at the Field
The creation of a computer data bank for the Cerro Prieto Geothermal Field, resulted from the need for fast and flexible management of the increasing and voluminous information generated from the large number of wells drilled in recent years. The data are needed for updating the thermodynamic evolution of the field in order to define field history and validate mathematical analyses applications. This data bank compiles 20 files with all technical information issued from the time of initial field exploration to the end of 1986. To use the data bank, a series of programs and subroutines were created simultaneously for data base management to allow access and add new data as well as data analysis and data graphics. Tables of global statistics of the informations contained in the 20 files are shown in the paper, as an example of one application of the general use of the data base. For particular and specific applications, depending on users’ needs for the data. 3 tabs., 1 fig.
Date:
January 20, 1987
Creator:
Olmos, Miguel Angel Ayuso
Object Type:
Article
System:
The UNT Digital Library
Chemical and Isotopic Evidence of Steam Upflow and Partial Condensation in Los Azufres Reservoir
Data of chemical and isotopic composition of fluids from Los Azufres wells, collected over a two year period, provide evidence of a process of upward flow and partial condensation of steam in the reservoir, which explains part of the previously reported heterogeneity in isotopic composition of the liquid phase (Nieva et al, 1983). For the southern part of the field, a direct correlation is found between chloride and oxygen-18 concentrations, and an inverse correlation between these parameters and deuterium and carbon dioxide concentrations in the liquid phase of the reservoir. Chloride ion concentrations increase gradually from ca 660 ppm in the production zones of shallow wells to ca 1900 ppm in the case of deep wells. This observation agrees with predictions based on the well-known model for vapor dominated systems of White et al (1971). For the northern part of the field the same correlations are observed, except for the deuterium concentration which in this case correlates directly with oxygen-18. It is concluded that the same process of steam upflow occurs in the northern section but that some other process — perhaps a mixture with other hydrothermal fluid — is also occurring. 3 tabs., 16 refs., 8 figs.
Date:
January 20, 1987
Creator:
Nieva, D.; Verma, M.; Santoyo, E.; Barragan, R.M.; Portugal, E.; Ortiz, J. et al.
Object Type:
Article
System:
The UNT Digital Library
Chickasha Daily Express (Chickasha, Okla.), Vol. 95, No. 327, Ed. 1 Tuesday, January 20, 1987
Daily newspaper from Chickasha, Oklahoma that includes local, state, and national news along with advertising.
Date:
January 20, 1987
Creator:
Drew, Charles C.
Object Type:
Newspaper
System:
The Gateway to Oklahoma History
Conceptual Model of the Klamath Falls, Oregon Geothermal Area
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. 1 tab., 8 figs., 21 refs.
Date:
January 20, 1987
Creator:
Prucha, R. H.; Benson, S. M. & Witherspoon, P. A.
Object Type:
Article
System:
The UNT Digital Library
Decline Curve Analysis of Production Data from the Geysers Geothermal Field
Production data for over two hundred wells at The Geysers geothermal field were compiled and analysed. Decline curves for groups of wells with 5, 10, and 40 acre spacing are presented and compared to curves published previously by Budd (1972) and Dykstra (1981). Decline curves for several individual wells and leases are discussed to illustrate the effects of well spacing and location, as well as the heterogeneous nature of the reservoir. 6 figs., 1 tab., 10 refs.
Date:
January 20, 1987
Creator:
Ripperda, M. & Bodvarsson, G.S.
Object Type:
Article
System:
The UNT Digital Library
Development and Exploitation of Low Enthalpy Geothermal Systems, Example of "The Dogger" in the Paris Basin, France
A feature of French geothermal engineering is the development of industrial projects in normal gradient, non-convective areas. The economic feasibility of exploiting wells producing between 150 and 350 m{sup 3}/h at temperatures from 55° to 85° from depths of 1,500 to 2,000 meters, in sedimentary basins with normal gradient, for direct heat production has been proved by 50 plants providing heating for over 500,000 people during the last few years. This opens new possibilities for geothermal energy development the world over, in particular for areas where heat consumption is higher than 2,500 Tons oil equivalent (Toe)/year over several square kilometers. The recent and rapid development of geothermal projects in France, in particular in the Paris Basin has provided much more information on the characteristics of the Jurassic Dogger, which is the unit tapped by geothermal doublets (one production and one injection well). Detailed study of the Dogger reservoir in the Paris Basin is one of the main objectives of the IMRG research and development program drawn up in 1983. The preliminary results presented here are oriented towards (1) improved knowledge of the potential geothermal resources, and (2) analysis of optimum development conditions. 1 tab., 7 refs., 9 figs.
Date:
January 20, 1987
Creator:
Rojas, J.; Menjoz, A.; Martin, J. C.; Criaud, A. & Fouillac, C.
Object Type:
Article
System:
The UNT Digital Library
Development Drilling, Testing and Initial Production of the Beowawe Geothermal Field
The Beowawe geothermal field in north central Nevada is generating 16MW using two production wells (Ginn 1-13 and 2-13) and one injection well (Batz). Drilling the second production well (Chevron Ginn 2-13) in 1985 led to the discovery of a second productive strand of the Malpais fault zone. The wells are completed in the Malpais fault zone and are capable of producing 420+°F geothermal fluid at rates exceeding 1,000,000 lbs/hr. Initial testing suggests that the completion zones of the two production wells have no pressure communication, therefore providing what is essentially a second production zone for future development. Injection of produced fluids into a fault parallel with the Malpais shows no pressure communication with other wells. One year of production in the system shows no pressure depletion or enthalpy decline in the producing area. 1 tab., 6 figs., 5 refs.
Date:
January 20, 1987
Creator:
Hoang, V.T.; James, E.D. & Epperson, I.J.
Object Type:
Article
System:
The UNT Digital Library
Discharging Through an Orifice Determines Steam-Water Enthalpy
Abstract: A wide range of steam-water mixtures was discharged to the atmosphere through a 10.7 mm diameter orifice which was sharp-edged with a minuscule throat pressure tapping. The ratio of throat pressure to up-stream pressure was found sensitive to dryness fraction over the whole range studied from 0.03 to 1.0. The technique (employing large orifices) has the potential of identifying the unknown enthalpy of geothermal wells discharging large flows. Contrariwise, a nozzle (rounded entry orifice) was found remarkably _insensitive_ over most of the dryness range and hence is useless for such determinations; however, it can be used to measure the flow-rate when enthalpy is known.
Date:
January 20, 1987
Creator:
James, Russell
Object Type:
Article
System:
The UNT Digital Library
The Electrokinetic Mechanism of Hydrothermal-Circulation-Related and Production-Induced Self-Potentials
Self-potential (SP) surveys were carried out on a number of geothermal areas in Japan during the last decade. In most cases SP anomalies of positive polarity are found to overlie high temperature upflow zones. Streaming potential generated by hydrothermal circulation (Ishido, 1981) is considered to be the most likely cause of the observed positive anomalies. Repeated surveys conducted on the Nigorikawa caldera in Japan detected a change in SP induced by production of geothermal fluids. The observed change is dipolar in waveform and can also be attributed to an electrokinetic mechanism. 6 figs., 14 refs.
Date:
January 20, 1987
Creator:
Ishido, T.; Kikuchi, T. & Sugihara, M.
Object Type:
Article
System:
The UNT Digital Library
Fieldwide Chemical and Isotopic Gradients in Steam from the Geysers
Strong fieldwide gradients from southeast to northwest in gas/steam and {delta}{sup 18}O have been found in steam produced from wells at The Geysers. These gradients result from recharge from the southeast that has increased liquid saturation in the southern part of the reservoir and flushed gases and high {delta}{sup 18}O connate waters to the north and out of the system through surface vents. Variations in the steepness of the gradients are probably related to major venting in the Big Geysers area. Although lateral steam flow and condensation subsequent to flushing explain some local gradients in the southern area, these processes cannot explain the fieldwide variations. 1 tab., 24 refs., 5 figs.
Date:
January 20, 1987
Creator:
Truesdell, A. H.; Haizlip, J. R.; Box, W. T., Jr. & D'Amore, F.
Object Type:
Article
System:
The UNT Digital Library
Fracture Detection in Geothermal Wells Drilled in Volcanic Rocks
The Phlegrean Fields, close to Naples, are the site of important geothermal activity. The formations are volcanic and mostly tuffites. They are originally very tight but the geothermal alteration locally produces fractures with large increase in permeability. The lack of geological markers makes well-to-well correlation quite difficult. Thus the local detection of fractured zones in each well is very important for the evaluation of its potential. The Mofete 8 D well is a typical example. A rather complete logging program was run for fracture detection. Standard methods turned out to be disappointing. However several non-standard detectors were found to be very consistent and, later on, in excellent agreement with the analysis of cuttings. They are derived from the Dual Laterolog, the SP, the Temperature log and, most particularly, the Acoustic Waveforms from the Long Spacing Sonic. The Dual Laterolog and the Temperature Log indicate invasion by fresh and cold mud filtrate; the SP behaves as in a typical Sand-Shale sequence. Sonic Waveforms were first analyzed by a purely empirical method derived from consistent log patterns. A practical algorithm compares the total energy measured in each of the two fixed time windows located the one before, the other after the fluid …
Date:
January 20, 1987
Creator:
Gonfalini, Mauro; Chelini, Walter; Cheruvier, Etienne; Suau, Jean & Klopf, Werner
Object Type:
Article
System:
The UNT Digital Library
Gas Geochemistry of the Dogger Geothermal Aquifer (Paris Basin, France)
The low enthalpy program developed in the Paris Basin provides the opportunity for studying the gas geochemistry of the calcareous aquifer of the Dogger. Hydrocarbons and CO{sub 2} are mainly biogenic, He displays high concentrations. He, Ar and N{sub 2} have multiple origins (radioactive decay, atmospheric migration, biochemical processes). The distribution of the gases in the zones of the basin varies in relation to the general chemistry, sedimentology and hydrodynamics. The gas geothermometers do not apply to this environment but useful estimations of the redox potential of the fluid can be derived from CO{sub 2}/CH{sub 4} and N{sub 2}/NH{sub 4}{sup +} ratios. H{sub 2} and H{sub 2}S are involved in corrosion processes and scaling in the pipes. 12 refs., 3 figs., 2 tabs.
Date:
January 20, 1987
Creator:
Criaud, A.; Fouillac, C.; Marty, B.; Brach, M. & Wei, H. F.
Object Type:
Article
System:
The UNT Digital Library
Gas Geothermometry Based on CO Content--Application in Italian Geothermal Fields
This paper discusses gas chemical equilibria in geothermal reservoirs involving the species CO{sub 2}, CH{sub 4}, CO, H{sub 2}S, H{sub 2}, and H{sub 2}O. A set of equations is developed correlating ratios of gas to CO{sub 2} with temperature, steam fraction, and CO{sub 2} partial pressure in the reservoir. A method for solving the set of nonlinear equations is proposed. These equations do not involve discharge gas/total H{sub 2}O ratios and may therefore be used for fumaroles and hot-spring fluids. Applications to fumarole and well-discharge fluid compositions in Italian geothermal fields show good correlations between temperatures calculated with this method and the temperatures measured in the reservoir (between 140° to 330°C). 5 tabs., 1 fig., 19 refs.
Date:
January 20, 1987
Creator:
D'Amore, F.; Fancelli, R.; Saracco, L. & Truesdell, A.H.
Object Type:
Article
System:
The UNT Digital Library
Geochemistry and the Exploration of the Ngawha Geothermal System, New Zealand
The Ngawha geothermal system is atypical of New Zealand geothermal systems, being located outside the Taupo Volcanic Zone, and contained in tight sedimentary structures. Early geochemical surveys of surface discharges indicated a high gas, high borate fluid, discharging in small quantities, to the surface. An initial well (drilled in the early 1960’s, to 500m) produced a vary gassy fluid before calciting. Deeper wells drilled and discharged in the early 1980’s produced large flows of high gas fluid (up to 3wt%), at enthalpies around 1000 kj/kg. These low energy contents coupled with a low water to rock ratio, a very fractured structure, and consequent expected changes in the production fluid following exploitation, let do large scale exploitation plans being scrapped in 1982. The close attention to geochemical studies before and during the drilling operations enabled predictions of fluid type, physical conditions at depth, fluid disposal problems, and hydrologic reservoir models that have proved to be correct. The project served to indicate the value of comprehensive exploration strategies which precede the drilling phase, and the further value of, in particular, geochemical studies as an integral part of well testing procedures, for the updating of reservoir models. The close and open cooperation amongst …
Date:
January 20, 1987
Creator:
Sheppard, D.S.
Object Type:
Article
System:
The UNT Digital Library
Geochemistry and Tracer Behavior During a Thirty Day Flow Test of the Fenton Hill HDR Reservoir
During the most recent circulating flow test of the Fenton Hill Hot Dry Rock (HDR) geothermal reservoir, the geochemical behavior of the produced fluid was monitored continuously to determine the concentrations of dissolved anions and cations and dissolved gases. Chemistry results have aided in the development of reservoir models and in the determination of potential chemistry-related operation problems such as corrosion and gas handling in future energy extraction tests. Results of two radioactive tracer experiments suggest flow through a large, highly-fractured region of rock. This rock volume is equivalent to a sphere of diameter approximately equal to the separation distance between the injection and production points in the two wells. 1 tab., 10 figs., 7 refs.
Date:
January 20, 1987
Creator:
Robinson, Bruce A.; Aguilar, Ronald G.; Kanaori, Yuji; Trujillo, Pat; Counce, Dale; Birdsell, Stephen A. et al.
Object Type:
Article
System:
The UNT Digital Library
Geothermal Energy - An Emerging Resource
Address on the Department of Energy's overall energy policy, the role of alternative energy sources within the policy framework, and expectations for geothermal energy. Commendation of the industry's decision to pursue the longer-term field effort while demand for geothermal energy is low, and thus prepare for a substantial geothermal contribution to the nation's energy security.
Date:
January 20, 1987
Creator:
Berg, John R.
Object Type:
Article
System:
The UNT Digital Library