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Title: Field-project designs for carbon dioxide sequestration and enhanced coalbed methane production

Abstract

Worldwide concerns about global warming and possible contributions to it from anthropogenic carbon dioxide have become important during the past several years. Coal seams may make excellent candidates for CO{sub 2} sequestration; coal-seam sequestration could enhance methane production and improve sequestration economics. Reservoir-simulation computations are an important component of any engineering design before carbon dioxide is injected underground. We have performed such simulations for a hypothetical pilot-scale project in representative coal seams. In these simulations we assume four horizontal production wells that form a square, that is, two wells drilled at right angles to each other forming two sides of a square, with another pair of horizontal wells similarly drilled to form the other two sides. Four shorter horizontal wells are drilled from a vertical well at the center of the square, forming two straight lines orthogonal to each other. By modifying coal properties, especially sorption rate, we have approximated different types of coals. By varying operational parameters, such as injector length, injection well pressure, time to injection, and production well pressure, we can evaluate different production schemes to determine an optimum for each coal type. Any optimization requires considering a tradeoff between total CO{sub 2} sequestered and the ratemore » of methane production. Values of total CO{sub 2} sequestered and methane produced are presented for multiple coal types and different operational designs. 30 refs., 11 figs., 1 tab.« less

Authors:
; ; ; ;  [1]
  1. EG&G Technical Services, Morgantown, WV (United States). National Energy Technology Laboratory
Publication Date:
OSTI Identifier:
20688434
Resource Type:
Journal Article
Resource Relation:
Journal Name: Energy and Fuels; Journal Volume: 19; Journal Issue: 6; Other Information: sjikic@netl.doe.gov
Country of Publication:
United States
Language:
English
Subject:
01 COAL, LIGNITE, AND PEAT; FIELD TESTS; CARBON SEQUESTRATION; COAL SEAMS; METHANE; COMPUTERIZED SIMULATION; UNDERGROUND STORAGE; CARBON DIOXIDE

Citation Formats

W. Neal Sams, Grant Bromhal, Sinisha Jikich, Turgay Ertekin, and Duane H. Smith. Field-project designs for carbon dioxide sequestration and enhanced coalbed methane production. United States: N. p., 2005. Web. doi:10.1021/ef049667n.
W. Neal Sams, Grant Bromhal, Sinisha Jikich, Turgay Ertekin, & Duane H. Smith. Field-project designs for carbon dioxide sequestration and enhanced coalbed methane production. United States. doi:10.1021/ef049667n.
W. Neal Sams, Grant Bromhal, Sinisha Jikich, Turgay Ertekin, and Duane H. Smith. Thu . "Field-project designs for carbon dioxide sequestration and enhanced coalbed methane production". United States. doi:10.1021/ef049667n.
@article{osti_20688434,
title = {Field-project designs for carbon dioxide sequestration and enhanced coalbed methane production},
author = {W. Neal Sams and Grant Bromhal and Sinisha Jikich and Turgay Ertekin and Duane H. Smith},
abstractNote = {Worldwide concerns about global warming and possible contributions to it from anthropogenic carbon dioxide have become important during the past several years. Coal seams may make excellent candidates for CO{sub 2} sequestration; coal-seam sequestration could enhance methane production and improve sequestration economics. Reservoir-simulation computations are an important component of any engineering design before carbon dioxide is injected underground. We have performed such simulations for a hypothetical pilot-scale project in representative coal seams. In these simulations we assume four horizontal production wells that form a square, that is, two wells drilled at right angles to each other forming two sides of a square, with another pair of horizontal wells similarly drilled to form the other two sides. Four shorter horizontal wells are drilled from a vertical well at the center of the square, forming two straight lines orthogonal to each other. By modifying coal properties, especially sorption rate, we have approximated different types of coals. By varying operational parameters, such as injector length, injection well pressure, time to injection, and production well pressure, we can evaluate different production schemes to determine an optimum for each coal type. Any optimization requires considering a tradeoff between total CO{sub 2} sequestered and the rate of methane production. Values of total CO{sub 2} sequestered and methane produced are presented for multiple coal types and different operational designs. 30 refs., 11 figs., 1 tab.},
doi = {10.1021/ef049667n},
journal = {Energy and Fuels},
number = 6,
volume = 19,
place = {United States},
year = {Thu Dec 01 00:00:00 EST 2005},
month = {Thu Dec 01 00:00:00 EST 2005}
}
  • In this work, the Palmer-Mansoori model for coal shrinkage and permeability increases during primary methane production was rewritten to also account for coal swelling caused by CO{sub 2} sorption. The generalized model was added to a compositional, dual porosity coalbed-methane reservoir simulator for primary (CBM) and ECBM production. A standard five-spot of vertical wells and representative coal properties for Appalachian coals was used. Simulations and sensitivity analyses were performed with the modified simulator for nine different parameters, including coal seam and operational parameters and economic criteria. The coal properties and operating parameters that were varied included Young's modulus, Poisson's ratio,more » cleat porosity, and injection pressure. The economic variables included CH{sub 4}, price, Col Cost, CO{sub 2} credit, water disposal cost, and interest rate. Net-present value (NPV) analyses of the simulation results included profits resulting from CH{sub 4}, production and potential incentives for sequestered CO{sub 2}, This work shows that for some coal seams, the combination of compressibility, cleat porosity, and shrinkage/swelling of the coal may have a significant impact on project economics.« less
  • Measurements of sorption isotherms and transport properties of CO2 in coal cores are important for designing enhanced coalbed methane/CO2 sequestration field projects. Sorption isotherms measured in the lab can provide the upper limit on the amount of CO2 that might be sorbed in these projects. Because sequestration sites will most likely be in unmineable coals, many of the coals will be deep and under considerable lithostatic and hydrostatic pressures. These lithostatic pressures may significantly reduce the sorption capacities and/or transport rates. Consequently, we have studied apparent sorption and diffusion in a coal core under confining pressure. A core from themore » important bituminous coal Pittsburgh #8 was kept under a constant, three-dimensional external stress; the sample was scanned by X-ray computer tomography (CT) before, then while it sorbed, CO2. Increases in sample density due to sorption were calculated from the CT images. Moreover, density distributions for small volume elements inside the core were calculated and analyzed. Qualitatively, the computerized tomography showed that gas sorption advanced at different rates in different regions of the core, and that diffusion and sorption progressed slowly. The amounts of CO2 sorbed were plotted vs. position (at fixed times) and vs. time (for various locations in the sample). The resulting sorption isotherms were compared to isotherms obtained from powdered coal from the same Pittsburgh #8 extended sample. The results showed that for this single coal at specified times, the apparent sorption isotherms were dependent on position of the volume element in the core and the distance from the CO2 source. Also, the calculated isotherms showed that less CO2 was sorbed than by a powdered (and unconfined) sample of the coal. Changes in density distributions during the experiment were also observed. After desorption, the density distribution of calculated volume elements differed from the initial distribution, suggesting hysteresis and a possible rearrangement of coal structure due to CO2 sorption.« less
  • A thorough study of the sorption behavior of coals to methane and carbon dioxide (CO{sub 2}) is critical for carbon sequestration in coal seams and enhanced coalbed methane recovery. This paper discusses the results of an ad/de-sorption study of methane and CO{sub 2}, in single gas environment, on a set of coal samples taken from the San Juan and Illinois Basins. The results indicate that, under similar temperature and pressure conditions, coals exhibit higher affinity to CO{sub 2} as compared to methane and that the preferential sorption ratio varies between 2:1 and 4:1. Furthermore, the experimental data were modeled usingmore » Langmuir, BET, and Dubinin-Polanyi equations. The accuracy of the models in quantifying coal-gas sorption was compared using an error analysis technique. The Dubinin-Radushkevich equation failed to model the coal-gas sorption behavior satisfactorily. For methane, Langmuir, BET, and Dubinin-Astakhov (D-A) equations all performed satisfactorily within comparable accuracy. However, for CO{sub 2}, the performance of the D-A equation was found to be significantly better than the other two. Overall, the D-A equation fitted the experimental sorption data the best, followed by the Langmuir and BET equations. Since the D-A equation is capable of deriving isotherms for any temperature using a single isotherm, thus providing added flexibility to model the temperature variation due to injection/depletion, this is the recommended model to use. 49 refs., 9 figs., 5 tabs.« less
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