Simulating carbon dioxide sequestration/ECBM production in coal seams: Effects of permeability anisotropies and the diffusion-time constant

Duane H. Smith, Grant Bromhal, W. Neal Sams, Sinisha Jikich, Turgay Ertekin

Research output: Contribution to journalArticle

19 Citations (Scopus)

Abstract

Coalbed methane now accounts for a significant fraction of domestic natural-gas production. Injection of carbon dioxide (CO2) into coal seams is a promising technology for reducing anthropogenic greenhouse-gas emissions and increasing ultimate production of coalbed methane. Reservoir simulations are an inexpensive method for designing field projects and predicting optimal tradeoffs between maximum sequestration and maximum methane production. Optimum project design and operation are expected to depend on the anisotropy of the permeability along the face-cleat and butt-cleat directions, the spacing between cleats, and the sorption isotherms for methane and CO2. In this work, a dual-porosity coalbed-methane simulator is used to model primary and secondary production of methane from coal for a variety of coal properties and operational parameters. It is assumed that the face and butt cleats are perpendicular to each other, with horizontal wells parallel to one type of cleat and perpendicular to the other. The well pattern consists of four horizontal production wells that form a rectangle, with four shorter horizontal wells centered within the rectangle. In the limiting case of no permeability anisotropy, the central wells form a "plus" sign within the square of production wells. All wells are operated as producers of methane and water until a specified reservoir pressure is reached, after which the central wells are operated as injectors for CO2. Production of methane continues until the CO2 concentration in the produced gas is too high. The simulation results predict the optimum lengths of the injection wells along the face- and butt-cleat directions and show how these optimum lengths depend on the permeabilities in the two directions. If the cleat spacing is sufficiently small, and diffusion of the gas through the pores to the cleats is sufficiently rapid, instantaneous sorption may be assumed. Otherwise, the field performance depends on the diffusion-time constant that characterizes the rate of transfer between the cleats and the coal matrix. The pressures at which the injection wells are operated also affect the amounts of CO2 sequestered through the pressures and volumes of the sorption isotherms.

Original languageEnglish (US)
Pages (from-to)156-163
Number of pages8
JournalSPE Reservoir Evaluation and Engineering
Volume8
Issue number2
StatePublished - Apr 1 2005

Fingerprint

coal seam
carbon sequestration
Carbon dioxide
Anisotropy
anisotropy
Coal
permeability
well
Methane
methane
coalbed methane
Sorption
Horizontal wells
sorption
Isotherms
coal
isotherm
spacing
effect
Gas emissions

All Science Journal Classification (ASJC) codes

  • Fuel Technology
  • Energy Engineering and Power Technology
  • Geology

Cite this

Smith, Duane H. ; Bromhal, Grant ; Sams, W. Neal ; Jikich, Sinisha ; Ertekin, Turgay. / Simulating carbon dioxide sequestration/ECBM production in coal seams : Effects of permeability anisotropies and the diffusion-time constant. In: SPE Reservoir Evaluation and Engineering. 2005 ; Vol. 8, No. 2. pp. 156-163.
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Simulating carbon dioxide sequestration/ECBM production in coal seams : Effects of permeability anisotropies and the diffusion-time constant. / Smith, Duane H.; Bromhal, Grant; Sams, W. Neal; Jikich, Sinisha; Ertekin, Turgay.

In: SPE Reservoir Evaluation and Engineering, Vol. 8, No. 2, 01.04.2005, p. 156-163.

Research output: Contribution to journalArticle

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T1 - Simulating carbon dioxide sequestration/ECBM production in coal seams

T2 - Effects of permeability anisotropies and the diffusion-time constant

AU - Smith, Duane H.

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N2 - Coalbed methane now accounts for a significant fraction of domestic natural-gas production. Injection of carbon dioxide (CO2) into coal seams is a promising technology for reducing anthropogenic greenhouse-gas emissions and increasing ultimate production of coalbed methane. Reservoir simulations are an inexpensive method for designing field projects and predicting optimal tradeoffs between maximum sequestration and maximum methane production. Optimum project design and operation are expected to depend on the anisotropy of the permeability along the face-cleat and butt-cleat directions, the spacing between cleats, and the sorption isotherms for methane and CO2. In this work, a dual-porosity coalbed-methane simulator is used to model primary and secondary production of methane from coal for a variety of coal properties and operational parameters. It is assumed that the face and butt cleats are perpendicular to each other, with horizontal wells parallel to one type of cleat and perpendicular to the other. The well pattern consists of four horizontal production wells that form a rectangle, with four shorter horizontal wells centered within the rectangle. In the limiting case of no permeability anisotropy, the central wells form a "plus" sign within the square of production wells. All wells are operated as producers of methane and water until a specified reservoir pressure is reached, after which the central wells are operated as injectors for CO2. Production of methane continues until the CO2 concentration in the produced gas is too high. The simulation results predict the optimum lengths of the injection wells along the face- and butt-cleat directions and show how these optimum lengths depend on the permeabilities in the two directions. If the cleat spacing is sufficiently small, and diffusion of the gas through the pores to the cleats is sufficiently rapid, instantaneous sorption may be assumed. Otherwise, the field performance depends on the diffusion-time constant that characterizes the rate of transfer between the cleats and the coal matrix. The pressures at which the injection wells are operated also affect the amounts of CO2 sequestered through the pressures and volumes of the sorption isotherms.

AB - Coalbed methane now accounts for a significant fraction of domestic natural-gas production. Injection of carbon dioxide (CO2) into coal seams is a promising technology for reducing anthropogenic greenhouse-gas emissions and increasing ultimate production of coalbed methane. Reservoir simulations are an inexpensive method for designing field projects and predicting optimal tradeoffs between maximum sequestration and maximum methane production. Optimum project design and operation are expected to depend on the anisotropy of the permeability along the face-cleat and butt-cleat directions, the spacing between cleats, and the sorption isotherms for methane and CO2. In this work, a dual-porosity coalbed-methane simulator is used to model primary and secondary production of methane from coal for a variety of coal properties and operational parameters. It is assumed that the face and butt cleats are perpendicular to each other, with horizontal wells parallel to one type of cleat and perpendicular to the other. The well pattern consists of four horizontal production wells that form a rectangle, with four shorter horizontal wells centered within the rectangle. In the limiting case of no permeability anisotropy, the central wells form a "plus" sign within the square of production wells. All wells are operated as producers of methane and water until a specified reservoir pressure is reached, after which the central wells are operated as injectors for CO2. Production of methane continues until the CO2 concentration in the produced gas is too high. The simulation results predict the optimum lengths of the injection wells along the face- and butt-cleat directions and show how these optimum lengths depend on the permeabilities in the two directions. If the cleat spacing is sufficiently small, and diffusion of the gas through the pores to the cleats is sufficiently rapid, instantaneous sorption may be assumed. Otherwise, the field performance depends on the diffusion-time constant that characterizes the rate of transfer between the cleats and the coal matrix. The pressures at which the injection wells are operated also affect the amounts of CO2 sequestered through the pressures and volumes of the sorption isotherms.

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