How Permeability Depends on Stress and Pore Pressure in Coalbeds: A New Model

Palmer, Ian; Mansoori, J.

doi:10.2523/36737-ms

Cited by 69 publications

(101 citation statements)

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“…All the results suggest that the trend of the proposed model results matches the permeability changes from the previous testing data. Similar matches were also found in the research of Palmer and Mansoori (1996) and Cui and Bustin (2005). However, compared with the magnitude of previous testing data, the permeability ratio of the coal permeability model proposed in this study is quite small.…”

Section: Discussionsupporting

confidence: 71%

“…Experimental efforts and model developments have been exerted to reveal coal-gas permeability and its evolution. Stress state and effective stress are always considered as an important factor for coal permeability (Gray 1987;McKee et al 1987;Palmer and Mansoori 1996;Enever and Henning 1997). Because of the pores in coal matrix, the percolation of coal methane becomes a reality.…”

mentioning

confidence: 99%

“…Shi and Durucan (2004a, b) used the conclusion of Gray (1987) and considered a pore pressure-dependent permeability model for gas desorbing coalbeds under uniaxial strain conditions. Palmer and Mansoori (1996) proposed a widely used model (called P&M model) in which permeability was a function of effective stress and shrinkage. Numerous studies have been conducted based on the P&M model (Pekot and Reeves 2002;Palmer et al 2007;Clarkson 2009).…”

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confidence: 99%

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Coal permeability model on the effect of gas extraction within effective influence zone

Xie

Gao

et al. 2015

Geomech. Geophys. Geo-energ. Geo-resour.

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In situ gas extraction is the main measure adopted by mines to achieve mining safety standards. Coal permeability is significantly influenced by coal shrinkage during gas release. Based on effective stress and additional damage that resulted from gas extraction, a unique model was proposed to describe the spatial and temporal distribution of coal permeability within the effective influence zone. Calculation models for the conditions of one and two extracting boreholes were developed. A parametric study on both two models was also conducted, in which the effect of extraction time, extraction pressure, interval between two boreholes, and extraction pressure combination were qualitatively analyzed. The results demonstrated that with the increase of extraction time, gas extraction can result in less permeability reduction in the beginning but can enhance permeability. Coal permeability obviously increases when extraction time increases but gradually stabilizes, presenting ''high middle and low around'' surrounding the extracting borehole. Meanwhile, a decreasing relative amplification implies that permeability ratio does not increase linearly with the increase in extraction pressure. Both intervals between two extracting boreholes and different combinations of extraction pressure significantly influence the distribution of coal permeability. A comparison with some previous permeability studies was conducted to validate the proposed model, and the predicted evolution results matched the permeability testing data. In conclusion, the proposed model is consistent with the phenomenon in real engineering, and the model results can provide preliminary guidance for the design of extracting borehole distribution.

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Section: Discussionsupporting

confidence: 71%

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confidence: 99%

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confidence: 99%

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Coal permeability model on the effect of gas extraction within effective influence zone

Xie

Gao

et al. 2015

Geomech. Geophys. Geo-energ. Geo-resour.

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“…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%

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

Robertson

Christiansen

2006

SPE Eastern Regional Meeting

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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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A transverse isotropic model for microporous solids: Application to coal matrix adsorption and swelling

et al. 2013

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[1] Understanding the adsorption-induced swelling in coal is critical for predictable and enhanced coal bed methane production. The coal matrix is a natural anisotropic disordered microporous solid. We develop an elastic transverse isotropic poromechanical model for microporous solids which couples adsorption and strain through adsorption stress functions and expresses the adsorption isotherm as a multivariate function depending on fluid pressure and solid strains. Experimental data from the literature help invert the anisotropic adsorptive-mechanical properties of Brzeszcze coal samples exposed to CO 2 . The main findings include the following: (1) adsorption-induced swelling can be modeled by including fluid-specific and pressure-dependent adsorption stress functions into equilibrium equations, (2) modeling results suggest that swelling anisotropy is mostly caused by anisotropy of the solid mechanical properties, and (3) the total amount of adsorbed gas measured by immersing coal in the adsorbate overestimates adsorption amount compared to in situ conditions up to 20%. The developed fully coupled model can be upscaled to determine the coal seam permeability through permeability-stress relationships.

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How Permeability Depends on Stress and Pore Pressure in Coalbeds: A New Model

Cited by 69 publications

References 0 publications

Coal permeability model on the effect of gas extraction within effective influence zone

Coal permeability model on the effect of gas extraction within effective influence zone

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

A transverse isotropic model for microporous solids: Application to coal matrix adsorption and swelling

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