Model study of the influence of matrix shrinkage on absolute permeability of coal bed reservoirs

Levine, Jeffrey R.

doi:10.1144/gsl.sp.1996.109.01.14

Cited by 363 publications

(262 citation statements)

References 13 publications

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“…19 The above equation can then be rewritten as It has also been shown that for isotropic media, the volumetric strain can be closely approximated by three times the linear strain. 20 On a large scale, coal is not isotropic because of its layered characteristic, but on a small (matrix block) scale, there is evidence that coal behaves in an isotropic manner and that linear strain in all directions is equivalent to onethird of the volumetric strain, 21 which supports the assumption that coal is an isotropic medium on a small scale. Substituting linear strain ( lm ) for one-third the volumetric strain results in the following equation: Sorption-Induced Strain.…”

Section: Factors That Affect Cleat Widthmentioning

confidence: 94%

“…For example, porosity, sorption- 6 Young et al 24 Sawyer et al 4 Gash 25 Levine 21 Palmer and Mansoori 6 Gray 3 Seidle et al 9 Shi and Durucan 8 0.339 Young's modulus, E, psi 300,000 to 600,000 124,000 to 445,000 392,000 500,000…”

Section: Sensitivity Of Model To Input Parametersmentioning

confidence: 99%

“…Levine 21 Palmer and Mansoori 6 Gray 3 Seidle et al 9 393,500 The following sensitivity figures were plotted using data shown in Table 1. The "high" curves use the extreme upper values, and "low" curves use the extreme lower values, and the average curves use the average values.…”

Section: Sensitivity Of Model To Input Parametersmentioning

confidence: 99%

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A Permeability Model for Coal and Other Fractured, Sorptive-Elastic Media

Robertson

Christiansen

2006

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This paper describes the derivation of a new equation that can be used to model the permeability behavior of a fractured, sorptive-elastic media, such as coal, under variable stress conditions commonly used during measurement of permeability data in the laboratory. The model is derived for cubic geometry under biaxial or hydrostatic confining pressures. The model is also designed to handle changes in permeability caused by adsorption and desorption of gases from the matrix blocks. The model equations can be used to calculate permeability changes caused by the production of methane from coal as well as the injection of gases, such as carbon dioxide, for sequestration in coal. Sensitivity analysis of the model found that each of the input variables can have a significant impact on the outcome of the permeability forecast as a function of changing pore pressure; thus, accurate input data are essential. The permeability model can also be used as a tool to determine input parameters for field simulations by curve-fitting laboratory-generated permeability data. The new model is compared to two other widely used coal permeability models using a hypothetical coal with average properties. IntroductionDuring gas production from a coal seam, as reservoir (pore) pressure is lowered, gas molecules, such as methane, are desorbed from the matrix and travel by diffusion to the cleat (natural fracture) system where they are conveyed to producing wells. Fluid movement in coal is controlled by slow diffusion within the coal matrix and described by Darcy flow within the fracture system, which is much faster than the contribution of diffusion. A coal formation is typically treated as a fractured reservoir with respect to fluid flow; meaning that the sole contributor to the overall permeability of the reservoir is the fracture system and the contribution of diffusion through the matrix to total flow is neglected. Coalbeds are unlike other non-reactive fractured reservoirs because of their ability to adsorb (or desorb) large amounts of gas, which causes swelling (or shrinkage) of the matrix blocks.Coal has the capacity to adsorb large amounts of gases because of their typically large internal surface area, which can range from 30 m 2 /g to 300 m 2 /g. 1 Some gases, such as carbon dioxide, have a higher affinity for the coal surfaces than others, such as nitrogen. Knowledge of how the adsorption or desorption of gases affects coal permeability is important not only to operations involving the production of natural gas from coal beds, but also to the design and operation of projects to sequester greenhouse gases in coal beds. 2 Laboratory measurements of permeability using coal samples can be used to gain insight into field-scale permeability changes and to determine key coal property values necessary for field-scale simulation.A number of permeability models derived for sorptiveelastic media such as coals have been detailed in the literature and include those proposed by: Gray 3 in 1987, Sawyer et al. 4

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Section: Factors That Affect Cleat Widthmentioning

confidence: 94%

Section: Sensitivity Of Model To Input Parametersmentioning

confidence: 99%

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A Permeability Model for Coal and Other Fractured, Sorptive-Elastic Media

Robertson

Christiansen

2006

All Days

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“…Sorption of gases on coal results in matrix deformation, a well-accepted phenomenon in CBM research community. Several researchers [Levine, 1996;Harpalani and Mitra, 2010] have proposed a Langmuir-type model to fit the volumetric strain, given as follows:…”

Section: Effect Of Sorption-induced Strainmentioning

confidence: 99%

Evaluation of in situ stress changes with gas depletion of coalbed methane reservoirs

Liu

Harpalani

2014

JGR Solid Earth

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A sound knowledge of the stress path for coalbed methane (CBM) reservoirs is critical for a variety of applications, including dynamic formation stability evaluation, long-term gas production management, and carbon sequestration in coals. Although this problem has been extensively studied for traditional oil and gas reservoirs, it is somewhat unclear for CBM reservoirs. The difference between the stress paths followed in the two reservoir types is expected to be significant given the unique sorption-induced deformation phenomenon associated with gas production from coal. This results in an additional reservoir volumetric strain, which induces a rather "abnormal" loss of horizontal stress with depletion, leading to continuous changes in the subsurface formation stresses, both effective as well as total. It is suspected that stress changes within the reservoir triggers formation failure after significant depletion. This paper describes an experimental study, carried out to measure the horizontal stress under in situ depletion conditions. The results show that the horizontal stress decreases linearly with depletion under in situ conditions. The dynamic stress evolution is theoretically analyzed, based on modified poroelasticity associated with sorption-induced strain effect. Additionally, the failure tendency of the reservoir under in situ conditions is analyzed using the traditional Mohr-Coulomb failure criterion. The results indicate that depletion may lead to coal failure, particularly in deeper coalbeds and ones exhibiting large matrix shrinkage.

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“…(20) for selected cleat volume compressibility values. The range of E (2,000 to 4,000 MPa) and  (0.2 to 0.4) reported by Levin (1996) is adopted here.…”

Section: Constant Confining Pressure Vs Uniaxial Strain Conditionmentioning

confidence: 99%