Enhanced Geothermal Systems (EGS) Comparing Water with CO2 as Heattransmission Fluids PDF Download
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Languages : en
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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.
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Languages : en
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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.
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Languages : en
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It has been suggested that enhanced geothermal systems (EGS) may be operated with supercritical CO2 instead of water as heat transmission fluid (D.W. Brown, 2000). Such a scheme could combine recovery of geothermal energy with simultaneous geologic storage of CO2, a greenhouse gas. At geothermal temperature and pressure conditions of interest, the flow and heat transfer behavior of CO2 would be considerably different from water, and chemical interactions between CO2 and reservoir rocks would also be quite different from aqueous fluids. This paper summarizes our research to date into fluid flow and heat transfer aspects of operating EGS with CO2. (Chemical aspects of EGS with CO2 are discussed in a companion paper; Xu and Pruess, 2010.) Our modeling studies indicate that CO2 would achieve heat extraction at larger rates than aqueous fluids. The development of an EGS-CO2 reservoir would require replacement of the pore water by CO2 through persistent injection. We find that in a fractured reservoir, CO2 breakthrough at production wells would occur rapidly, within a few weeks of starting CO2 injection. Subsequently a two-phase water-CO2 mixture would be produced for a few years, followed by production of a single phase of supercritical CO2. Even after single-phase production conditions are reached, significant dissolved water concentrations will persist in the CO2 stream for many years. The presence of dissolved water in the production stream has negligible impact on mass flow and heat transfer rates.
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Languages : en
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Responding to the need to reduce atmospheric emissions of carbon dioxide, Donald Brown (2000) proposed a novel enhanced geothermal systems (EGS) concept that would use CO2 instead of water as heat transmission fluid, and would achieve geologic sequestration of CO2 as an ancillary benefit. Following up on his suggestion, we have evaluated thermophysical properties and performed numerical simulations to explore the fluid dynamics and heat transfer issues in an engineered geothermal reservoir that would be operated with CO2. We find that CO2 is superior to water in its ability to mine heat from hot fractured rock. CO2 also has certain advantages with respect to wellbore hydraulics, where larger compressibility and expansivity as compared to water would increase buoyancy forces and would reduce the parasitic power consumption of the fluid circulation system. While the thermal and hydraulic aspects of a CO2-EGS system look promising, major uncertainties remain with regard to chemical interactions between fluids and rocks. An EGS system running on CO2 has sufficiently attractive features to warrant further investigation.
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Languages : en
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There is growing interest in the novel concept of operating Enhanced Geothermal Systems (EGS) with CO2 instead of water as heat transmission fluid. Initial studies have suggested that CO2 will achieve larger rates of heat extraction, and can offer geologic storage of carbon as an ancillary benefit. Fluid-rock interactions in EGS operated with CO2 are expected to be vastly different in zones with an aqueous phase present, as compared to the central reservoir zone with anhydrous supercritical CO2. Our numerical simulations of chemically reactive transport show a combination of mineral dissolution and precipitation effects in the peripheral zone of the systems. These could impact reservoir growth and longevity, with important ramifications for sustaining energy recovery, for estimating CO2 loss rates, and for figuring tradeoffs between power generation and geologic storage of CO2.
Author: Hejuan Liu
Publisher: Cuvillier Verlag
ISBN: 3736948425
Category : Science
Languages : en
Pages : 285
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In this dissertation, three simulators (i.e. TOUGH2MP, TOUGHREACT and FLAC3D) were used to simulate the complex physical and chemical interactions induced by CO2 sequestration. The simulations were done instages, ranging from the two phase (water and CO2) fluid flow (H2), through coupled hydro-mechanical effects (H2M) and geochemical responses (i.e. CO2-water-rock interactions (H2C)), to the extension of CCS to CCUS by the application of combined geothermal production and CO2 sequestration technologies. The findings of this study are essential for a thorough understanding of the complex interactions in the multiphase, multicomponent porous media controlled by different physical and chemical mechanisms. Furthermore, the simulation results will provide an invaluable reference for field operations in CCS projects, especially for the full-integration pilot scale CCS project launched in the Ordos Basin. Subsequently, a preliminary site selection scheme for the combined geothermal production and CO2 sequestration was set up, which considered various factorsinvolved in site selection, ranging from safety, economical, environmental and technical issues. This work provides an important framework for the combined geothermal production and CO2 sequestration project. However, further numerical and field studies are still needed to improve on a series of criteria and related parameters necessary for a better understanding of the technology.
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Languages : en
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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.
Author: Tushar K. Ghosh
Publisher: Springer Science & Business Media
ISBN: 9400714025
Category : Business & Economics
Languages : en
Pages : 736
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This second volume of Energy Resources and Systems is focused on renewable energy resources. Renewable energy mainly comes from wind, solar, hydropower, geothermal, ocean, bioenergy, ethanol and hydrogen. Each of these energy resources is important and growing. For example, high-head hydroelectric energy is a well established energy resource and already contributes about 20% of the world’s electricity. Some countries have significant high-head resources and produce the bulk of their electrical power by this method. However, the bulk of the world’s high-head hydroelectric resources have not been exploited, particularly by the underdeveloped countries. Low-head hydroelectric is unexploited and has the potential to be a growth area. Wind energy is the fastest growing of the renewable energy resources for the electricity generation. Solar energy is a popular renewable energy resource. Geothermal energy is viable near volcanic areas. Bioenergy and ethanol have grown in recent years primarily due to changes in public policy meant to encourage its usage. Energy policies stimulated the growth of ethanol, for example, with the unintended side effect of rise in food prices. Hydrogen has been pushed as a transportation fuel. The authors want to provide a comprehensive series of texts on the interlinking of the nature of energy resources, the systems that utilize them, the environmental effects, the socioeconomic impact, the political aspects and governing policies. Volume 1 on Fundamentals and Non Renewable Resources was published in 2009. It blends fundamental concepts with an understanding of the non-renewable resources that dominate today’s society. The authors are now working on Volume 3, on nuclear advanced energy resources and nuclear batteries, consists of fusion, space power systems, nuclear energy conversion, nuclear batteries and advanced power, fuel cells and energy storage. Volume 4 will cover environmental effects, remediation and policy. Solutions to providing long term, stable and economical energy is a complex problem, which links social, economical, technical and environmental issues. It is the goal of the four volume Energy Resources and Systems series to tell the whole story and provide the background required by students of energy to understand the complex nature of the problem and the importance of linking social, economical, technical and environmental issues.
Author: Yinhui Zuo
Publisher: Frontiers Media SA
ISBN: 2832500161
Category : Science
Languages : en
Pages : 364
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Author: Jianxing Liao
Publisher: Cuvillier Verlag
ISBN: 3736962428
Category : Technology & Engineering
Languages : en
Pages : 180
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In this dissertation, two specific numerical models have been developed to address the issues associated with utilization of supercritical CO2, like fracture creation, proppant placement and fracture closure in unconventional gas reservoirs, reservoir stimulation, heat production and CO2 sequestration in deep geothermal reservoirs, respectively. In unconventional gas reservoir, the model consisting of classic fracture model, proppant transport model as well as temperature-sensitive fracturing fluids (CO2, thickened CO2 and guar gum) has been integrated into the popular THM coupled framework (TOUGH2MP-FLAC3D), which has the ability to simulate single fracture propagation driven by different fracturing fluids in non-isothermal condition. To characterize the fracture network propagation and internal multi fluids behavior in deep geothermal reservoirs, an anisotropic permeability model on the foundation of the continuum anisotropic damage model has been developed and integrated into the popular THM coupled framework (TOUGH2MP-FLAC3D) as well. This model has the potential to simulate the reservoir stimulation and heat extraction based on a CO2-EGS concept.
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Category : Geothermal engineering
Languages : en
Pages : 232
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