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Stragegies to Detect Hidden Geothermal Systems Based on Monitoringand Analysis of CO2 in the Near-Surface Environment

Description: We investigate the potential for CO2 monitoring in thenear-surface environment as an approach to exploration for hiddengeothermal systems. Numerical simulations of CO2 migration from a modelhidden geothermal system show that CO2 concentrations can reach highlevels in the shallow subsurface even for relatively low CO2 fluxes.Therefore, subsurface measurements offer an advantage over above-groundmeasurements which are affected by winds that rapidly disperse CO2. Tomeet the challenge of detecting geothermal CO2 emissions within thenatural background variability of CO2, we propose an approach thatintegrates available detection and monitoring techniques with statisticalanalysis and modeling.
Date: March 29, 2005
Creator: Lewicki, Jennifer L. & Oldenburg, Curtis M.
Partner: UNT Libraries Government Documents Department

Fracture Characterization in Enhanced Geothermal Systems by Wellbore and Reservoir Analysis

Description: This report highlights the work that was done to characterize fractured geothermal reservoirs using production data. That includes methods that were developed to infer characteristic functions from production data and models that were designed to optimize reinjection scheduling into geothermal reservoirs, based on these characteristic functions. The characterization method provides a robust way of interpreting tracer and flow rate data from fractured reservoirs. The flow-rate data are used to infer the interwell connectivity, which describes how injected fluids are divided between producers in the reservoir. The tracer data are used to find the tracer kernel for each injector-producer connection. The tracer kernel describes the volume and dispersive properties of the interwell flow path. A combination of parametric and nonparametric regression methods were developed to estimate the tracer kernels for situations where data is collected at variable flow-rate or variable injected concentration conditions. The characteristic functions can be used to calibrate thermal transport models, which can in turn be used to predict the productivity of geothermal systems. This predictive model can be used to optimize injection scheduling in a geothermal reservoir, as is illustrated in this report.
Date: June 30, 2012
Creator: Roland N. Horne, Kewen Li, Mohammed Alaskar, Morgan Ames, Carla Co, Egill Juliusson, Lilja Magnusdottir
Partner: UNT Libraries Government Documents Department

Enhanced Geothermal Systems (EGS) comparing water with CO2 as heattransmission fluids

Description: This paper summarizes our research to date into operatingEGS with CO2. Our modeling studies indicate that CO2 would achieve morefavorable heat extraction than aqueous fluids. The peculiarthermophysicalproperties of CO2 give rise to unusual features in the dependence ofenergy recovery on thermodynamic conditions and time. Preliminarygeochemical studies suggest that CO2 may avoid unfavorable rock-fluidinteractions that have been encountered in water-basedsystems. To morefully evaluate the potential of EGS with CO2 will require an integratedresearch programme of model development, and laboratory and fieldstudies.
Date: November 1, 2007
Creator: Pruess, Karsten
Partner: UNT Libraries Government Documents Department

Temporary Bridging Agents for use in Drilling and Completion of Enhanced Geothermal Systems

Description: CSI Technologies, in conjunction with Alta Rock Energy and the University of Utah have undergone a study investigating materials and mechanisms with potential for use in Enhanced Geothermal Systems wells as temporary diverters or lost circulation materials. Studies were also conducted with regards to particle size distribution and sealing effectiveness using a lab-scale slot testing apparatus to simulate fractures. From the slot testing a numerical correlation was developed to determine the optimal PSD for a given fracture size. Field trials conducted using materials from this study were also successful.
Date: December 21, 2011
Creator: Watters, Larry; Watters, Jeff; Sutton, Joy; Combs, Kyle; Bour, Daniel; Petty, Susan et al.
Partner: UNT Libraries Government Documents Department

Geothermal Permeability Enhancement - Final Report

Description: The overall objective is to apply known permeability enhancement techniques to reduce the number of wells needed and demonstrate the applicability of the techniques to other undeveloped or under-developed fields. The Enhanced Geothermal System (EGS) concept presented in this project enhances energy extraction from reduced permeability zones in the super-heated, vapor-dominated Aidlin Field of the The Geysers geothermal reservoir. Numerous geothermal reservoirs worldwide, over a wide temperature range, contain zones of low permeability which limit the development potential and the efficient recovery of heat from these reservoirs. Low permeability results from poorly connected fractures or the lack of fractures. The Enhanced Geothermal System concept presented here expands these technologies by applying and evaluating them in a systematic, integrated program.
Date: June 30, 2009
Creator: Beall, Joe & Walters, Mark
Partner: UNT Libraries Government Documents Department

Telluric and D.C. Resistivity Techniques Applied to the Geophysical Investigation of Basin and Range Geothermal Systems, Part III: The Analysis of Data From Grass Valley, Nevada

Description: This paper contains a detailed interpretation of E-field ratio telluric, bipole-dipole resistivity mapping, and dipole-dipole resistivity data obtained in the course of geophysical exploration of the Leach Hot Springs area of Grass Valley, Nevada. Several areas are singled out as being worthy of further investigation of their geothermal potential. Comparison of the three electrical exploration techniques indicates that: the bipole-dipole resistivity mapping method is the least useful; the dipole-dipole resistivity method can be very useful, but is, for practical purposes, exceptionally expensive and difficult to interpret; the E-field ratio telluric method can be a highly successful reconnaissance technique for delineating structures and relating the resistivities of different regions within the survey area.
Date: June 1, 1977
Creator: Beyer, J.H.
Partner: UNT Libraries Government Documents Department


Description: Reactive tracers have long been considered a possible means of measuring thermal drawdown in a geothermal system, before significant cooling occurs at the extraction well. Here, we examine the sensitivity of the proposed method to evaluate reservoir cooling and demonstrate that while the sensitivity of the method as generally proposed is low, it may be practical under certain conditions.
Date: October 1, 2010
Creator: Plummer, Mitchell A.; Palmer, Carl D.; Mattson, Earl D.; Redden, George D. & Hull, Laurence C.
Partner: UNT Libraries Government Documents Department

Further Developments on the Geothermal System Scoping Model: Preprint

Description: This paper discusses further developments and refinements for the uses of the Geothermal System Scoping Model in an effort to provide a means for performing a variety of trade-off analyses of surface and subsurface parameters, sensitivity analyses, and other systems engineering studies in order to better inform R&D direction and investment for the development of geothermal power into a major contributor to the U.S. energy supply.
Date: July 1, 2010
Creator: Antkowiak, M.; Sargent, R. & Geiger, J. W.
Partner: UNT Libraries Government Documents Department

Creation of an Enhanced Geothermal System through Hydraulic and Thermal Stimulation

Description: This report describes a 10-year DOE-funded project to design, characterize and create an Engineered Geothermal System (EGS) through a combination of hydraulic, thermal and chemical stimulation techniques. Volume 1 describes a four-year Phase 1 campaign, which focused on the east compartment of the Coso geothermal field. It includes a description of the geomechanical, geophysical, hydraulic, and geochemical studies that were conducted to characterize the reservoir in anticipation of the hydraulic stimulation experiment. Phase 1 ended prematurely when the drill bit intersected a very permeable fault zone during the redrilling of target stimulation well 34-9RD2. A hydraulic stimulation was inadvertently achieved, however, since the flow of drill mud from the well into the formation created an earthquake swarm near the wellbore that was recorded, located, analyzed and interpreted by project seismologists. Upon completion of Phase 1, the project shifted focus to a new target well, which was located within the southwest compartment of the Coso geothermal field. Volume 2 describes the Phase 2 studies on the geomechanical, geophysical, hydraulic, and geochemical aspects of the reservoir in and around target-stimulation well 46A-19RD, which is the deepest and hottest well ever drilled at Coso. Its total measured depth exceeding 12,000 ft. It spite of its great depth, this well is largely impermeable below a depth of about 9,000 ft, thus providing an excellent target for stimulation. In order to prepare 46A-19RD for stimulation, however, it was necessary to pull the slotted liner. This proved to be unachievable under the budget allocated by the Coso Operating Company partners, and this aspect of the project was abandoned, ending the program at Coso. The program then shifted to the EGS project at Desert Peak, which had a goal similar to the one at Coso of creating an EGS on the periphery of an existing geothermal reservoir. ...
Date: April 15, 2013
Creator: Rose, Peter Eugene
Partner: UNT Libraries Government Documents Department

Induced seismicity associated with enhanced geothermal system

Description: Enhanced Geothermal Systems (EGS) offer the potential to significantly add to the world energy inventory. As with any development of new technology, some aspects of the technology has been accepted by the general public, but some have not yet been accepted and await further clarification before such acceptance is possible. One of the issues associated with EGS is the role of microseismicity during the creation of the underground reservoir and the subsequent extraction of the energy. The primary objectives of this white paper are to present an up-to-date review of the state of knowledge about induced seismicity during the creation and operation of enhanced geothermal systems, and to point out the gaps in knowledge that if addressed will allow an improved understanding of the mechanisms generating the events as well as serve as a basis to develop successful protocols for monitoring and addressing community issues associated with such induced seismicity. The information was collected though literature searches as well as convening three workshops to gather information from a wide audience. Although microseismicity has been associated with the development of production and injection operations in a variety of geothermal regions, there have been no or few adverse physical effects on the operations or on surrounding communities. Still, there is public concern over the possible amount and magnitude of the seismicity associated with current and future EGS operations. It is pointed out that microseismicity has been successfully dealt with in a variety of non-geothermal as well as geothermal environments. Several case histories are also presented to illustrate a variety of technical and public acceptance issues. It is concluded that EGS Induced seismicity need not pose any threat to the development of geothermal resources if community issues are properly handled. In fact, induced seismicity provides benefits because it can be used as a ...
Date: September 26, 2006
Creator: Majer, Ernest; Majer, Ernest L.; Baria, Roy; Stark, Mitch; Oates, Stephen; Bommer, Julian et al.
Partner: UNT Libraries Government Documents Department

Imaging Multi-Dimensional Electrical Resistivity Structure as a Tool in Developing Enhanced Geothermal Systems (EGS)

Description: The overall goal of this project has been to develop desktop capability for 3-D EM inversion as a complement or alternative to existing massively parallel platforms. We have been fortunate in having a uniquely productive cooperative relationship with Kyushu University (Y. Sasaki, P.I.) who supplied a base-level 3-D inversion source code for MT data over a half-space based on staggered grid finite differences. Storage efficiency was greatly increased in this algorithm by implementing a symmetric L-U parameter step solver, and by loading the parameter step matrix one frequency at a time. Rules were established for achieving sufficient jacobian accuracy versus mesh discretization, and regularization was much improved by scaling the damping terms according to influence of parameters upon the measured response. The modified program was applied to 101 five-channel MT stations taken over the Coso East Flank area supported by the DOE and the Navy. Inversion of these data on a 2 Gb desktop PC using a half-space starting model recovered the main features of the subsurface resistivity structure seen in a massively parallel inversion which used a series of stitched 2-D inversions as a starting model. In particular, a steeply west-dipping, N-S trending conductor was resolved under the central-west portion of the East Flank. It may correspond to a highly saline magamtic fluid component, residual fluid from boiling, or less likely cryptic acid sulphate alteration, all in a steep fracture mesh. This work gained student Virginia Maris the Best Student Presentation at the 2006 GRC annual meeting.
Date: December 31, 2007
Creator: Wannamaker, Philip E.
Partner: UNT Libraries Government Documents Department

Identifying Fracture Types and Relative Ages Using Fluid Inclusion Stratigraphy

Description: Enhanced Geothermal Systems (EGS) are designed to recover heat from the subsurface by mechanically creating fractures in subsurface rocks. Understanding the life cycle of a fracture in a geothermal system is fundamental to the development of techniques for creating fractures. Recognizing the stage of a fracture, whether it is currently open and transmitting fluids; if it recently has closed; or if it is an ancient fracture would assist in targeting areas for further fracture stimulation. Identifying dense fracture areas as well as large open fractures from small fracture systems will also assist in fracture stimulation selection. Geothermal systems are constantly generating fractures, and fluids and gases passing through rocks in these systems leave small fluid and gas samples trapped in healed microfractures. Fluid inclusions trapped in minerals as the fractures heal are characteristic of the fluids that formed them, and this signature can be seen in fluid inclusion gas analysis. Our hypothesis is that fractures over their life cycle have different chemical signatures that we can see in fluid inclusion gas analysis and by using the new method of fluid inclusion stratigraphy (FIS) the different stages of fractures, along with an estimate of fracture size can be identified during the well drilling process. We have shown with this study that it is possible to identify fracture locations using FIS and that different fractures have different chemical signatures however that signature is somewhat dependent upon rock type. Open, active fractures correlate with increase concentrations of CO2, N2, Ar, and to a lesser extent H2O. These fractures would be targets for further enhancement. The usefulness of this method is that it is low cost alternative to current well logging techniques and can be done as a well is being drilled.
Date: June 30, 2008
Creator: Dilley, Lorie M.; Norman, David & Owens, Lara
Partner: UNT Libraries Government Documents Department

On the production behavior of enhanced geothermal systems with CO2as working fluid

Description: Numerical simulation is used to evaluate mass flow and heatextraction rates from enhanced geothermal injection-production systemsthat are operated using either CO2 or water as heat transmission fluid.For a model system patterned after the European hot dry rock experimentat Soultz, we find significantly greater heat extraction rates for CO2 ascompared to water. The strong dependence of CO2 mobility (=density/viscosity) upon temperature and pressure may lead to unusualproduction behavior, where heat extraction rates can actually increasefor a time, even as the reservoir is subject to thermal depletion. Wepresent the first-ever three-dimensional simulations of CO2injection-production systems. These show strong effects of gravity onmass flow and heat extraction, due to the large contrast of CO2 densitybetween cold injection and hot production conditions. The tendency forpreferential flow of cold, dense CO2 along the reservoir bottom can leadto premature thermal breakthrough. The problem can be avoided byproducing from only a limited depth interval at the top of thereservoir.
Date: May 31, 2007
Creator: Pruess, K.
Partner: UNT Libraries Government Documents Department

Numerical studies of gravity effects in two-phase reservoirs

Description: Numerical studies are performed to investigate the effects of localized feed zones on the pressure transients in two-phase reservoirs. It is shown that gravity effects can significantly affect the pressure transients, because of the large difference in the density of liquid water and vapor. Pressure transients for shallow and deep feed zones and the resulting fluid flow patterns are discussed.
Date: June 1, 1986
Creator: Bodvarsson, G.S. & Cox, B.L.
Partner: UNT Libraries Government Documents Department

Modeling studies of geothermal systems with a free water surface

Description: A numerical simulator was developed for the modeling of air-steam-water systems. The simulator was applied to various problems involving injection into or production from a geothermal reservoir in hydraulic communication with a shallow free-surface aquifer. First, a one-dimensional column problem is considered and the water level movement during exploitation is studied using different capillary pressure functions. Second, a two-dimensional radial model is used to study and compare reservoir depletion for cases with and without a free-surface aquifer. Finally, the contamination of a shallow free-surface aquifer due to cold water injection is investigated. The primary aim of these studies is to obtain an understanding of the response of a reservoir in hydraulic communication with a unconfined aquifer during exploitation or injection and to determine under which circumstances conventional modeling techniques (fully saturated systems) can be applied to such systems.
Date: December 1, 1983
Creator: Bodvarsson, G.S. & Pruess, K.
Partner: UNT Libraries Government Documents Department

High Temperature Components of Magma-Related Geothermal Systems: An Experimental and Theoretical Approach

Description: This summarizes select components of a multi-faceted study of high temperature magmatic fluid behavior in shallow, silicic, volcano-plutonic geothermal systems. This work built on a foundation provided by DOE-supported advances made in our lab in understanding the physics and chemistry of the addition of HCI and other chlorides into the high temperature regions of geothermal systems. The emphasis of this project was to produce a model of the bolatile contributions from felsic magmatic systems to geothermal systems
Date: March 15, 2004
Creator: Candela, Philip A. & Piccoli, Philip M.
Partner: UNT Libraries Government Documents Department

Numerical models for the evaluation of geothermal systems

Description: We have carried out detailed simulations of various fields in the USA (Bada, New Mexico; Heber, California); Mexico (Cerro Prieto); Iceland (Krafla); and Kenya (Olkaria). These simulation studies have illustrated the usefulness of numerical models for the overall evaluation of geothermal systems. The methodology for modeling the behavior of geothermal systems, different approaches to geothermal reservoir modeling and how they can be applied in comprehensive evaluation work are discussed.
Date: August 1, 1986
Creator: Bodvarsson, G.S.; Pruess, K. & Lippmann, M.J.
Partner: UNT Libraries Government Documents Department

Reducing long-term reservoir performance uncertainty

Description: Reservoir performance is one of the key issues that have to be addressed before going ahead with the development of a geothermal field. In order to select the type and size of the power plant and design other surface installations, it is necessary to know the characteristics of the production wells and of the produced fluids, and to predict the changes over a 10--30 year period. This is not a straightforward task, as in most cases the calculations have to be made on the basis of data collected before significant fluid volumes have been extracted from the reservoir. The paper describes the methodology used in predicting the long-term performance of hydrothermal systems, as well as DOE/GTD-sponsored research aimed at reducing the uncertainties associated with these predictions. 27 refs., 1 fig.
Date: April 1, 1988
Creator: Lippmann, M.J.
Partner: UNT Libraries Government Documents Department

Enhanced Geothermal Systems (EGS) R&D Program, Status Report: Foreign Research on Enhanced Geothermal Systems

Description: This report reviews enhanced geothermal systems (EGS) research outside the United States. The term ''enhanced geothermal systems'' refers to the use of advanced technology to extract heat energy from underground in areas with higher than average heat flow but where the natural permeability or fluid content is limited. EGS covers the spectrum of geothermal resources from low permeability hydrothermal to hot dry rock.
Date: September 29, 2000
Creator: McLarty, Lynn & Entingh, Daniel
Partner: UNT Libraries Government Documents Department

Telluric and D.C. Resistivity Techniques Applied to the Geophysical Investigation of Basin and Range Geothermal Systems, Part II: A Numberical Model Study of the Dipole-Dipole and Schlumberger Resistivity Methods

Description: This paper is a two-dimensional numerical model study and comparison of the polar dipole-dipole and Schlumberger resistivity arrays. A catalog of dipole-dipole and Schlumberger apparent resistivity pseudo-sections is presented. It is concluded that: for the Schlumberger array, data can be accurately interpreted only if the resistivity structure is horizontally layered, and conductive bodies having a depth of burial greater than their width are not observed; for the dipole-dipole array, complex anomaly patterns unrelated in appearance to the causative structure result from simple models, hence, a familiarity with model results is essential to interpretation of these data.
Date: June 1, 1977
Creator: Beyer, J.H.
Partner: UNT Libraries Government Documents Department

Global Deployment of Geothermal Energy Using a New Characterization in GCAM 1.0

Description: This report documents modeling of geothermal energy in GCAM 1.0 (formerly MiniCAM) from FY2008 to FY2009, from the inputs to the U.S. Climate Change Technology Program report (Clarke et al., 2008a) to the present representation, which will be used in future work. To demonstrate the newest representation, we describe the procedure and outcome of six model runs that illustrate the potential role of geothermal energy in the U.S. and global regions through different futures climate policy, development and deployment of engineered, or enhanced, geothermal systems (EGS), and availability of other low-cost, low-carbon electricity generation technologies such as nuclear energy and carbon capture and storage (CCS).
Date: September 1, 2009
Creator: Hannam, Phil; Kyle, G. Page & Smith, Steven J.
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