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X-ray evidence for capillary pressure driven flow in preserved core from The Geysers

Description: Improved understanding of fluid storage and transport mechanisms relevant to The Geysers reservoir is fundamental to efficient and economic long term production of steam. X-ray computed tomographs of core from research borehole SB-15D made within 72 hours of drilling show characteristic x-ray attenuation profiles that can only be explained by imbibition of drilling fluid at reservoir conditions. The shape of the profile is highly diagnostic. Early time scans, when interpreted taking into account independent measurements of pore size distribution, permeabilities and capillary pressures for the rock matrix sampled by SB-15D, are consistent with strong capillary suctions for the recovered rocks. This indirect indication of imbibition under reservoir conditions, along with detailed analysis of x-ray attenuation in recovered core, suggests that water content was low in much of the preserved core. These measurements are part of a series of laboratory experiments monitored by x-ray methods intended to evaluate movement of various fluids to determine the relative importance capillarity, Darcy flow and vapor phase diffusion.
Date: March 1, 1997
Creator: Bonner, B.P.; Roberts, J.J. & Schneberk, D.J.
Partner: UNT Libraries Government Documents Department

Automatic history matching of geothermal field performance

Description: We have developed inverse modeling capabilities for the multiphase multicomponent numerical simulator TOUGH2 to facilitate automatic history matching, and parameter estimation based on data obtained during exploitation of Geothermal fields. The ITOUGH2 code allows one to estimate TOUGH2 input parameters based on any type of observation for which a corresponding TOUGH2 output can be calculated. Furthermore, a detailed residual and error analysis is performed, and the uncertainty of model predictions can be evaluated. This paper focuses on the solution of the inverse; problem, i.e. the determination of model-related parameters by automatically calibrating a conceptual model of the Geothermal system against data obtained during field operation. We first describe the modeling, approach used to simulate fluid and heat flow in fractured-porous media. The inverse problem is then formulated, followed by a brief discussion of the optimization algorithm. A sample problem is given to demonstrate the application of the method to Geothermal reservoir data.
Date: August 1, 1995
Creator: Finsterle, S. & Pruess, K>
Partner: UNT Libraries Government Documents Department

Chemical and isotopic characteristics of the coso east flankhydrothermal fluids: implications for the location and nature of the heatsource

Description: Fluids have been sampled from 9 wells and 2 fumaroles fromthe East Flank of the Coso hydrothermal system with a view toidentifying, if possible, the location and characteristics of the heatsource inflows into this portion of the geothermal field. Preliminaryresults show that there has been extensive vapor loss in the system, mostprobably in response to production. Wells 38A-9, 51-16 and 83A-16 showthe highest CO2-CO-CH4-H2 chemical equilibration temperatures, rangingbetween 300-340oC, and apart from 38A-9, the values are generally inaccordance with the measured temperatures in the wells. Calculatedtemperatures for the fractionation of 13C between CO2 and CH4 are inexcess of 400oC in fluids from wells 38A-9, 64-16-RD2 and 51A-16,obviously pointing to equilibrium conditions from deeper portions of thereservoir. Given that the predominant reservoir rock lithologies in theCoso system are relatively silicic (granitic to dioritic), the isotopicsignatures appear to reflect convective circulation and equilibrationwithin rocks close to the plastic-brittle transition. 3He/4He signatures,in conjunction with relative volatile abundances in the Coso fluids,point to a possibly altered mantle source for the heat sourcefluids.
Date: January 8, 2007
Creator: Christenson, B.W.; Kennedy, B.M.; Adams, M.C.; Bjornstad, S.C. & Buck, C.
Partner: UNT Libraries Government Documents Department

Inversion of synthetic aperture radar interferograms for sourcesof production-related subsidence at the Dixie Valley geothermalfield

Description: We used synthetic aperture radar interferograms to imageground subsidence that occurred over the Dixie Valley geothermal fieldduring different time intervals between 1992 and 1997. Linear elasticinversion of the subsidence that occurred between April, 1996 and March,1997 revealed that the dominant sources of deformation during this timeperiod were large changes in fluid volumes at shallow depths within thevalley fill above the reservoir. The distributions of subsidence andsubsurface volume change support a model in which reduction in pressureand volume of hot water discharging into the valley fill from localizedupflow along the Stillwater range frontal fault is caused by drawdownwithin the upflow zone resulting from geothermal production. Our resultsalso suggest that an additional source of fluid volume reduction in theshallow valley fill might be similar drawdown within piedmont faultzones. Shallow groundwater flow in the vicinity of the field appears tobe controlled on the NW by a mapped fault and to the SW by a lineament ofas yet unknown origin.
Date: July 1, 2006
Creator: Foxall, B. & Vasco, D.W.
Partner: UNT Libraries Government Documents Department

Mapping the Acid Stimulation in the Beowawe Geothermal Field Using Surface Electrical Potentials

Description: A surface electrical potential system was fielded during the chemical stimulation of the Rossi 21-19 well in the Beowawe Geothermal Field. The technique, which measures variations in resistivity resulting from the flow of conductive fluid into the reservoir, was not only shown to be highly sensitive, not only to the chemical treatment, but also to the in situ conductive zones before any acid injection. A review of the experiment and a preliminary interpretation of the data are presented. The data provide convincing evidence that it should be possible to map the treated zone as well as the primary pretreatment in situ conductive zones.
Date: December 15, 1983
Creator: Hart, Carolyne M.; Engi, Dennis & Morris, Harris E.
Partner: UNT Libraries Government Documents Department

Geophysical Exploration on the Structure of Volcanoes: Two Case Histories

Description: Geophysical methods of exploration were used to determine the internal structure of Koolau Volcano in Hawaii and of Rabaul Volcano in New Guinea. By use of gravity and seismic data the central vent or plug of Koolau Volcano was outlined. Magnetic data seem to indicate that the central plug is still above the Curie Point. If so, the amount of heat energy available is tremendous. As for Rabaul Volcano, it is located in a region characterized by numerous block faulting. The volcano is only a part of a large block that has subsided. Possible geothermal areas exist near the volcano but better potential areas may exist away from the volcano.
Date: January 1, 1974
Creator: Furumoto, A. S.
Partner: UNT Libraries Government Documents Department

Introduction to the proceedings of the Fourth Geothermal Reservoir Engineering Workshop, Stanford Geothermal Program

Description: The program committee for the Fourth Geothermal Workshop, presented in mid-December, 1978, decided that the format of the last two geothermal workshops should be continued; that is, the objective should be documented talks on field phenomena and reports on important results of research directly applicable to geothermal energy development. An arranged panel discussion of problems of common importance was also built into the program. Finally, it was decided to publish all submitted papers in the proceedings, but to select papers for presentation at the workshop program.
Date: January 1, 1978
Creator: Kruger, Paul & Ramey, Henry J., Jr.
Partner: UNT Libraries Government Documents Department

The New Zealand Goethermal Workshop, 1979, Part 2

Description: The New Zealand Geothermal Workshop took place on 29th-31st October 1979 at the University of Auckland. Over 100 participants were present (a list is included in this volume) with 6 overseas visitors, bring the number of countries represented (including the Institute's Fellows) to 14. Forty papers were presented over the three days of the meeting, together with 23 poster papers presented by the students of the Institute. This second Proceedings volume has been prepared as a supplement to the volume of conference papers distributed at the meeting, and was produced subsequent to the Workshop. The fist section of this volume includes additional papers presented at the meeting but not then available in printed form. The second part is a summary of the year's activities of the Geothermal Institute also presented in part at the meeting. These activities included some significant research contributions and original field investigations. Each fellow at the Institute was required as part of the course, to conduct an investigation and prepare a report which was presented at the Geothermal Workshop in a poster session. Abstracts of these project reports are included in this volume and five of the projects are reproduced in greater detail. Also included are outlines of the two original class projects conducted by the students and staff of the Institute, one a pre-feasibility study of the Ngawha Geothermal Field and the other an investigation of the Miranda Springs system. Finally, the lecture curriculum of the year's diploma course is presented in outline, together with the final examination papers. The two volumes of this document therefore include, as much as is possible within the restricted space, an overview of the Geothermal Institute's contribution to the development of geothermal energy together with a technical tribute to the many people involved in this very successful first year.
Date: January 1, 1979
Partner: UNT Libraries Government Documents Department

Session 20: Injection Overview

Description: The test program was initiated at the Raft River Geothermal Field in southern Idaho in September 1982. A series of eight short-term injection and backflow tests, followed by a long-term injection test, were conducted on one well in the field. Tracers were added during injection and monitored during backflow as well. The principal objective was to determine if tracers could be effectively used as a means to assess reservoir characteristics in a one-well test. The test program resulted in a unique data set which shows promise as a means to improve understanding of the reservoir characteristics. In December 1982, an RFP was issued to obtain an industrial partner to obtain follow-on data on the injection/backflow technique in a second field, and to study any alternate advanced concepts for injection testing which the industrial community might recommend. The East Mesa Geothermal Field was selected for the second test series. Two wells were utilized for testing, and a series of ten tests were conducted in July and August 1983, aimed principally at further evaluation of the injection/backflow technique.
Date: December 1, 1983
Creator: Prestwich, Susan
Partner: UNT Libraries Government Documents Department

The Response to Exploitation of Rotorua Geothermal Field

Description: The concern about possible decline in Whakarewarewa spring activity led to the creation of the rotorua Monitoring Program and the rotorua Task Force. Both will shortly issue their final reports (Ministry of Energy 1985a,b). Under the Monitoring Program a considerable database was collected about aquifer, well and spring behavior. From this it has been concluded that exploitation has had the following effects: (1) geothermal aquifer pressures have fallen by up to 0.5 bar; geothermal aquifer pressures beneath Whakarewarewa have fallen by about 0.2 bar; and (3) geothermal flow from Whakarewarewa has been reduced by about half. The effects on the springs could be reduced by reducing withdrawal particularly near Whaka, reinjection (including the use of downhole heat exchangers), or a combination of these.
Date: January 21, 1986
Creator: Grant, Malcolm A.
Partner: UNT Libraries Government Documents Department

The Ngatamariki Geothermal Field, NZ: Surface Manifestations - Past and Present

Description: The Ngatamariki geothermal field, located 7 km south of Orakeikorako, discharges dilute chloride-bicarbonate waters of almost neutral pH from springs mostly on the margins of the field. Rhyolite tuffs in the northwestern part of the field are weakly silicified, probably due to their having reacted with heated groundwaters. Sinter deposits are common at Ngatamariki but are mostly relict from former activity. In 1994, the natural heat loss from the field was 30 {+-} 5 MW{sub thermal}. There has been a shift of thermal activity southward over the past 60 years; the changes were recognized by comparing air photographs taken in 1941 and 1991. In 1948, a hydrothermal eruption deposited breccia around its crater, which is now occupied by a pool at 52.5 C. Another pool at 88 C, first noticed in 1993, deposits a mixture of silica and calcite.
Date: January 1, 1995
Creator: Brotheridge, J.M.A.; Browne, P.R.L. & Hochstein, M.P.
Partner: UNT Libraries Government Documents Department

Repeat Measurements of Seismic Noise at the Waiotapu Geothermal Area, North Island, NZ

Description: The amplitudes of seismic ground noise were remeasured at 66 sites in the Waiotapu and Reporoa geothermal areas in 1995 to determine whether amplitudes had changed since the first survey in 1970. In both 1995 and 1970 high levels of seismic noise occurred in two localities, one at Waiotapu and one at Reporoa. The elevated levels of seismic noise at most sites are thought to be caused by surface or near-surface geothermal activity. At seven sites in the Waiotapu area seismic noise levels were almost the same in 1995 as in 1970, indicating no change in the intensity of the source of the geothermal seismic noise. At most other sites the 1995 seismic noise levels were different to those measured in 1970, although at sites with high levels of seismic noise the differences were usually less than at sites with low levels of seismic noise.
Date: January 1, 1995
Creator: Whiteford, P.C.
Partner: UNT Libraries Government Documents Department

Relationship Between Heat Flows and Geological Structures in the Sichuan Basin, P.R. China

Description: Based on an extensive data collection and analysis, this research has provided reliable representations of the features of the geothermal fields, their heat flow, and relationships with geological structures in the Sichuan Basin. The isotherms below a depth of 1,000 m show high values in the Central Uplift and the Southwest Uplift, and low values in the Northwest and Southeast Depressions. These features probably indicate undulation of crystalline basement and structural depression. At depths greater than 3,000 m, the isotherms tend to become simpler and regionalized. The mean heat flow in the basin is 69.1 mW/m{sup 2}. In the Central Uplift, the Northwest Depression and the East of the basin, heat-flow values range from 58.6 to 71.2 mW/m{sup 2}, with a mean value of 66.1 mWE/m{sup 2}. In the south and southwest, it varies from 76.6 to 100.5 mW/m{sup 2}, with a mean value of 86.2 mW/m{sup 2}. High heat-flow values occur within the uplift of the crystalline basement in the southwest Sichuan, and the heat flow decreases from the south, through the central area, to the northwest.
Date: January 1, 1995
Creator: Zeng, Y.; Yu, H. & Wang, X.
Partner: UNT Libraries Government Documents Department

Publications and geothermal sample library facilities of the Earth Science Laboratory, University of Utah Research Institute

Description: The Earth Science Laboratory of the University of Utah Research Institute has been involved in research in geothermal exploration and development for the past eleven years. Our work has resulted in the publication of nearly 500 reports, which are listed in this document. Over the years, we have collected drill chip and core samples from more than 180 drill holes in geothermal areas, and most of these samples are available to others for research, exploration and similar purposes. We hope that scientists and engineers involved in industrial geothermal development will find our technology transfer and service efforts helpful.
Date: March 30, 1990
Creator: Wright, Phillip M.; Ruth, Kathryn A.; Langton, David R. & Bullett, Michael J.
Partner: UNT Libraries Government Documents Department

Greatly Enhanced Detectability of Geothermal Tracers Through Laser-Induced Fluorescence

Description: WE have successfully completed a four-year R and D project to greatly reduce the detection limit of fluorescent tracers through the use of emerging laser-excitation, optical fiber, and CCD-spectroscopy technologies. Whereas the efforts over the first two years were directed at demonstrating a reduction in the detection limit of fluorescent compounds by a factor of 100 and at identifying several new fluorescein-derived tracer candidates, our recent efforts were focused primarily on the field demonstration of new tracers having detection limits in the low parts-per-quadrillion range. During the summer of 2001, we initiated field tests at the Dixie Valley, Nevada and at the Beowawe, Nevada geothermal fields using very small quantities of the fluorescein-derivative 6-carboxyfluorescein. Subsequently, we succeeded in measuring sub-part-per-trillion quantities of that candidate tracer at both the Beowawe and Dixie Valley geothermal reservoirs-using approximately 530 g of tracer at each setting. Our studies indicate that we could have observed a breakthrough using only 0.53 g of 6-carboxyfluorescein. This represents a reduction by a factor of 170,000 below the mass of tracer used in a previous tracer test at Beowawe.
Date: October 30, 2002
Creator: Rose, Peter; Harris, Joel; Kilbourn, Phaedra; Kleimeyer, James & Carter, Troy
Partner: UNT Libraries Government Documents Department

A RESERVOIR ENGINEERING ANALYSIS OF A VAPOR-DOMINATED GEOTHERMAL FIELD

Description: The purpose of the study is to develop a simplified model to match past performances of a vapor-dominated geothermal reservoir and to predict future production rates and ultimate reserves. The data are fictitious, but are based on real data. A lumped parameter model was developed for the reservoir that is similar to the model developed by Brigham and Neri (1979, 1980) for the Gabbro zone, and a deliverability model was developed to predict the life and future producing rate declines of the reservoir. This report presents the development and results of this geothermal reservoir analysis.
Date: January 22, 1985
Creator: Dee, J.F. & Brigham, W.E.
Partner: UNT Libraries Government Documents Department

Nevada Southwest Regional Geothermal Development Operations Research Project. Appendix 8 of regional operations research program for development of geothermal energy in the Southwest United States. Final technical report, June 1977--August 1978

Description: By the end of the first year of the Southwest Regional Geothermal Project, the Nevada State Team has defined over 300 geothermal sites. Because of the multitude of sites and data, scenarios for this first project-year have been completed for the twenty-six Nevada Geothermal Areas, which include all the specific sites. It is not improbable that fully one-third of the sites will eventually prove to be of high to intermediate temperature (i.e. > 150 C and 90-150 C) resources. Low temperature sites are also prominent, not only in number, but also in their distribution--each of Nevada's 17 counties has several such sites.
Date: January 1, 1979
Creator: Clark, Noel A.; Booth, G. Martin, III; Weber, Dorismae & Helseth, Barbara K.
Partner: UNT Libraries Government Documents Department

Preliminary Gas and Isotope Geochemistry in the Rehai Geothermal Field, P.R. China

Description: Based on gas and sulphur isotopic composition, two types of steam in Rehai geothermal field are identified. One is with higher CO{sub 2} and H{sub 2}S concentration, the {delta}{sup 34}S of H{sub 2}S is in the range 2.49{per_thousand} to -1.04{per_thousand} (vs CDT), from which the H{sub 2}S-temperature is over than 250 C. The other is with lower CO{sub 2} and H{sub 2}S concentration, the {delta}{sup 34}S of H{sub 2}S is in the range -4.0{per_thousand} to -8.36{per_thousand}, from which the H{sub 2}S- and H{sub 2}-temperatures are 180 C-210 C, in good agreement with quartz temperature. The thermal water in the Rehai field is of local meteoric origin. Maximum {delta}{sup 18}O-value shift is less than 2.0{per_thousand} (vs SMOW). Mixing is widespread and could be identified on isotope and solute chemistry.
Date: January 1, 1995
Creator: P., Zhao & Z., Liao
Partner: UNT Libraries Government Documents Department

Use of Slim Holes for Geothermal Reservoir Assessment: An Update

Description: Production and injection data from slim holes and large-diameter wells in three (3) geothermal fields (Oguni, Sumikawa, Steamboat Hills) were examined to determine the effect of borehole diameter (1) on the discharge rate and (2) on the productivity/injectivity indices. For boreholes with liquid feedzones, maximum discharge rates scale with diameter according to a relationship previously derived by Pritchett. The latter scaling rule does not apply to discharge data for boreholes with two-phase feedzones. Data from Oguni and Sumikawa geothermal fields indicate that the productivity (for boreholes with liquid feeds) and injectivity indices are more or less equal. The injectivity indices for Sumikawa boreholes are essentially independent of borehole diameter. The latter result is at variance with Oguni data; both the productivity and injectivity indices for Oguni boreholes display a strong variation with borehole diameter. Based on the discharge and injection data from these three geothermal fields, the flow rate of large-diameter production wells with liquid feedzones can be predicted using data from slim holes.
Date: January 1, 1995
Creator: Garg, S.K.; Combs, J. & Goranson, C.
Partner: UNT Libraries Government Documents Department

Status of the TOUGH-FLAC simulator and recent applications related to coupled fluid flow and crustal deformations

Description: This paper presents recent advancement in and applications of TOUGH-FLAC, a simulator for multiphase fluid flow and geomechanics. The TOUGH-FLAC simulator links the TOUGH family multiphase fluid and heat transport codes with the commercial FLAC{sup 3D} geomechanical simulator. The most significant new TOUGH-FLAC development in the past few years is a revised architecture, enabling a more rigorous and tight coupling procedure with improved computational efficiency. The applications presented in this paper are related to modeling of crustal deformations caused by deep underground fluid movements and pressure changes as a result of both industrial activities (the In Salah CO{sub 2} Storage Project and the Geysers Geothermal Field) and natural events (the 1960s Matsushiro Earthquake Swarm). Finally, the paper provides some perspectives on the future of TOUGH-FLAC in light of its applicability to practical problems and the need for high-performance computing capabilities for field-scale problems, such as industrial-scale CO{sub 2} storage and enhanced geothermal systems. It is concluded that despite some limitations to fully adapting a commercial code such as FLAC{sup 3D} for some specialized research and computational needs, TOUGH-FLAC is likely to remain a pragmatic simulation approach, with an increasing number of users in both academia and industry.
Date: June 1, 2010
Creator: Rutqvist, J.
Partner: UNT Libraries Government Documents Department

Seismological Investigations at the Geysers Geothermal Field

Description: Two short (4 and 6 days) recording periods at The Geysers geothermal field provided useful data on two large refraction explosions and numerous microearthquakes. The vapor-dominated reservoir appears to be characterized by regionally anomalous high P- and S-wave velocities and low attenuation, but the anomaly seems to decrease, possibly reversing, with depth. Microearthquakes occur in a diffuse pattern, with no indication of dominant throughgoing faults and an absence of activity in the main production zone. Mechanisms are generally consistent with NE-SW compression. Occurrence rates indicate a slightly high incidence of smaller magnitude shocks. It is possible that the microearthquake activity is related to an expanding steam zone. While the present anomalies appear to delineate the reservoir, it is not certain that they would have been detectable in an exploration mode, prior to large-scale exploitation of the field.
Date: December 1, 1977
Creator: Majer, E. L. & McEvilly, T.V
Partner: UNT Libraries Government Documents Department

Challenges in determining b value in the Northwest Geysers

Description: Past analyses of the Gutenberg-Richter b-value in the Geysers and other geothermal settings have revealed a deviation from the assumed linear relationship in log space between magnitude and the number of earthquakes. In this study of the Northwest Geysers, we found a gently-sloping discontinuity in the b-value curve. This is especially apparent when comparing the least-squares fit (LSQ) of the curve to the fit obtained by the maximum likelihood estimation (MLE), a widely-respected method of analyzing magnitude-frequency relationships. This study will describe the assumptions made when using each of these two methods and will also explore how they can be used in conjunction to investigate the characteristics of the observed b-value curve. To understand whether slope-fit differences in the LSQR and MLE methods is due to physical properties of the system or due to artifacts from errors in sampling, it is extremely important to consider the catalog completeness, magnitude bin size, number of events, and differences in source mechanisms for the events comprising the study volume. This work will hopefully lead to informative interpretations of frequency-magnitude curves for the Northwest Geysers, a geothermal area of ongoing high-volume coldwater injection and steam production. Through this statistical investigation of the catalog contents, we hope to better understand the dominant source mechanisms and the role of injected fluids in the creation of seismic clustering around nearly 60 wells of varying depths and injection volumes.
Date: February 1, 2011
Creator: Saltiel, S.; Boyle, K. & Majer, E.
Partner: UNT Libraries Government Documents Department