Modelling permeability for coal reservoirs: A review of analytical models and testing data

Pan, Zhejun; Connell, Luke D.

doi:10.1016/j.coal.2011.12.009

Cited by 694 publications

(309 citation statements)

References 96 publications

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“…Pore-fracture structures in coal mass are the main galleries for gas migration and extraction (Pan and Connell 2012). Therefore, coal-mass permeability has an effective relationship with voids or fracture.…”

Section: Concepts and Basic Theoriesmentioning

confidence: 99%

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: Concepts and Basic Theoriesmentioning

confidence: 99%

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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“…Sorption of gases in coal has been studied for decades (Bae and Bhatia 2006;Billemont et al 2011Billemont et al , 2013Brochard et al 2012aBrochard et al , 2012bBusch and Gensterblum 2011;Busch et al 2003Busch et al , 2004Day et al 2008;Fitzgerald et al 2005;Gensterblum et al 2014;Goodman et al 2007;Krooss et al 2002;Li et al 2010;Ottiger et al 2008;Pini et al 2009Pini et al , 2010. Theoretical models have been developed and improved to study gas sorption on coal by several authors (Connell et al 2010;Lu and Connell 2007;Lu et al 2008;Pan and Connell 2007, 2012Sakurovs et al 2007; Vandamme et al 2010). They have applied different approaches to describe how sorption capacity, sorption rate, gas diffusion, and permeability are affected.…”

Section: Introductionmentioning

confidence: 99%

Molecular simulation studies of hydrocarbon and carbon dioxide adsorption on coal

et al. 2015

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Sorption isotherms of hydrocarbon and carbon dioxide (CO 2 ) provide crucial information for designing processes to sequester CO 2 and recover natural gas from unmineable coal beds. Methane (CH 4 ), ethane (C 2 H 6 ), and CO 2 adsorption isotherms on dry coal and the temperature effect on their maximum sorption capacity have been studied by performing combined Monte Carlo (MC) and molecular dynamics (MD) simulations at temperatures of 308 and 370 K (35 and 97°C) and at pressures up to 10 MPa. Simulation results demonstrate that absolute sorption (expressed as a mass basis) divided by bulk gas density has negligible temperature effect on CH 4 , C 2 H 6 , and CO 2 sorption on dry coal when pressure is over 6 MPa. CO 2 is more closely packed due to stronger interaction with coal and the stronger interaction between CO 2 molecules compared, respectively, with the interactions between hydrocarbons and coal and between hydrocarbons. The results of this work suggest that the ''a'' constant (proportional to T c 2 /P c ) in the Peng-Robinson equation of state is an important factor affecting the sorption behavior of hydrocarbons. CO 2 injection pressures of lower than 8 MPa may be desirable for CH 4 recovery and CO 2 sequestration. This study provides a quantitative understanding of the effects of temperature on coal sorption capacity for CH 4 , C 2 H 6 , and CO 2 from a microscopic perspective.

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“…Several mechanistic and geomechanical models have been proposed to model this phenomenon. A critical review of these models with field and experimental data reflecting those circumstances for which these models can be used is given in Pan and Connell (2012).…”

Section: Permeability Increase As a Results Of Matrix Shrinkage Duringmentioning

confidence: 99%

Production history matching to determine reservoir properties of important coal groups in the Upper Pottsville formation, Brookwood and Oak Grove fields, Black Warrior Basin, Alabama

Karacan

2013

Journal of Natural Gas Science and Engineering

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The Black Warrior Basin of Alabama is one of the most important coal mining and coalbed methane production areas in the United States. Methane control efforts through degasification that started almost 25 years ago for the sole purpose of ensuring mining safety resulted in more than 5000 coalbed methane wells distributed within various fields throughout the basin. The wells are completed mostly in the Pratt, Mary Lee, and Black Creek coal groups of the Upper Pottsville formation and present a unique opportunity to understand methane reservoir properties of these coals and to improve their degasification performances.The Brookwood and Oak Grove fields in the Black Warrior Basin are probably two of the most important fields in the basin due to current longwall coal mining activities. In this work, methane and water productions of 92 vertical wellbores drilled, some completed 20 years ago, over a current large coal mine district located in these two fields, were analyzed by history matching techniques. The boreholes were completed at the Mary Lee coal group, or at combinations of the Pratt, Mary Lee, and Black Creek groups. History matching models were prepared and performed according to properties of each coal group.Decline curve analyses showed that effective exponential decline rates of the wells were between 2% and 25% per year. Results of production history matching showed, although they varied by coal group, that pressure decreased as much as 80% to nearly 25 psi in some areas and resulted in corresponding decreases in methane content. Water saturation in coals decreased from 100% to between 20 and 80%, improving gas relative permeabilities to as much as 0.8. As a result of primary depletion, permeability of coal seams increased between 10 and 40% compared to their original permeability, which varied between 1 and 10 md depending on depth and coal seam. These results not only can be used for diagnostic and interpretation purposes, but can be used as parameter distributions in probabilistic simulations, as illustrated in the last section of this paper. They can also be used in conjunction with spatial modeling and geological considerations to calculate potential methane emissions in operating mines.

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Modelling permeability for coal reservoirs: A review of analytical models and testing data

Cited by 694 publications

References 96 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

Molecular simulation studies of hydrocarbon and carbon dioxide adsorption on coal

Production history matching to determine reservoir properties of important coal groups in the Upper Pottsville formation, Brookwood and Oak Grove fields, Black Warrior Basin, Alabama

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