A fully coupled coal deformation and compositional flow model for the control of the pre-mining coal seam gas extraction

Abstract Fully coupled compositional (coal seam gas and air) model of coal deformation, coal gas flow and transport, and air flow in coal seams is developed to better understand the gas drainage processes and the coal gas–air mixing mechanisms during pre-mining coal seem gas extraction. The model was first verified by showing that the modelled gas concentration profiles match reasonably with the in-situ measured ones. The verified model was then applied to evaluate how the drained gas concentration could be controlled under different conditions of the sealing length, the leakage rate and the leakage fracture width. These modelled results provides the basis of a new in-situ control technology of gas–air mixing, which uses fine expansive particles to seal the leakage fractures around the borehole. This technology has been commercially applied to enhance the concentration of the pre-mining gas drainage. The field test shows that the characteristics of the leakage fractures are greatly changed after the particles are injected into the in-seam drainage borehole when the gas concentration declines. Once the leakage fractures are blocked with the particles, the outside air is prevented from entering the coal seam. Thus, an ideal gas concentration can be maintained, and the duration of higher gas concentration is extended. For boreholes with an originally low gas concentration (0–30%), the new technology can increase the gas concentration by 10–65% and extend the production time by approximately two to three months. The total amount of gas drainage increases to 2000–3000 m 3 per borehole.

[1]  Sevket Durucan,et al.  Gas Storage and Flow in Coalbed Reservoirs: Implementation of a Bidisperse Pore Model for Gas Diffusion in Coal Matrix , 2005 .

[2]  Victor Rudolph,et al.  CO2 sequestration in coals and enhanced coalbed methane recovery: New numerical approach , 2010 .

[3]  Dong Chen,et al.  Interactions of multiple processes during CBM extraction: A critical review , 2011 .

[4]  Luke D. Connell,et al.  Observations from an enhanced gas recovery field trial for coal mine gas management , 2012 .

[5]  Ian Palmer,et al.  Permeability changes in coal: Analytical modeling , 2009 .

[6]  Sevket Durucan,et al.  Drawdown Induced Changes in Permeability of Coalbeds: A New Interpretation of the Reservoir Response to Primary Recovery , 2004 .

[7]  Xiexing Miao,et al.  Linking gas-sorption induced changes in coal permeability to directional strains through a modulus reduction ratio , 2010 .

[8]  Ian D. Palmer,et al.  How Permeability Depends on Stress and Pore Pressure in Coalbeds: A New Model , 1998 .

[9]  Khaled A. M. Gasem,et al.  Adsorption of Pure Methane, Nitrogen, and Carbon Dioxide and Their Binary Mixtures on Wet Fruitland Coal , 1994 .

[10]  C. Özgen Karacan,et al.  Coal mine methane: A review of capture and utilization practices with benefits to mining safety and to greenhouse gas reduction , 2011 .

[11]  Yu Qi-xiang,et al.  Development of Gas Extraction Technology in Coal Mines of China , 2009 .

[12]  Sohei Shimada,et al.  Displacement behavior of CH4 adsorbed on coals by injecting pure CO2, N2, and CO2–N2 mixture , 2005 .

[13]  X. Miao,et al.  Evaluation of stress-controlled coal swelling processes , 2010 .

[14]  W. P. Diamond.  Methane control for underground coal mines , 1994 .

[15]  Jiang Chenglin.  Study on Borehole Pressurized Sealing Technology for Gas Drainage Borehole in Mining Seam , 2011 .

[16]  Yu Wu,et al.  A dual poroelastic model for CO2-enhanced coalbed methane recovery , 2011 .

[17]  Derek Elsworth,et al.  How sorption-induced matrix deformation affects gas flow in coal seams: A new FE model , 2008 .

[18]  Luke D. Connell,et al.  Coupled flow and geomechanical processes during enhanced coal seam methane recovery through CO2 sequestration , 2009 .

[19]  E. Chibowski,et al.  Effect of different solid matrixes on surface free energy of EGDMA and TRIM polymers , 2010 .

[20]  Hongyan Qu,et al.  Multiphysics of coal-gas interactions: the scientific foundation for CBM extraction , 2010 .

[21]  W. Gunter,et al.  Large CO2 Sinks: Their role in the mitigation of greenhouse gases from an international, national (Canadian) and provincial (Alberta) perspective , 1998 .

[22]  Derek Elsworth,et al.  Evaluation of pore water pressure fluctuation around an advancing longwall face , 1999 .

[23]  Klaus Noack,et al.  Control of gas emissions in underground coal mines , 1998 .

[24]  Fangtian Wang,et al.  Implementation of underground longhole directional drilling technology for greenhouse gas mitigation in Chinese coal mines , 2012 .

[25]  S. R. Reeves,et al.  Modeling Coal Matrix Shrinkage and Differential Swelling with CO2 Injection for Enhanced Coalbed Methane Recovery and Carbon Sequestration Applications , 2002 .

[26]  Derek Elsworth,et al.  Three-dimensional effects of hydraulic conductivity enhancement and desaturation around mined panels , 1997 .

[27]  Larry Hughes,et al.  Canadian greenhouse gas emissions: 1990–2000 , 1997 .

[28]  John R. Seidle,et al.  Experimental Measurement of Coal Matrix Shrinkage Due to Gas Desorption and Implications for Cleat Permeability Increases , 1995 .

[29]  Cheng Zhai,et al.  Research on a New Composite Sealing Material of Gas Drainage Borehole and Its Sealing Performance , 2011 .

[30]  P. A. Riley,et al.  The measurement and comparison of methane drainage efficiencies in longwall advance and retreat workings , 1991 .

[31]  Luke D. Connell,et al.  Coupled flow and geomechanical processes during gas production from coal seams , 2009 .

[32]  Xiexing Miao,et al.  Development of anisotropic permeability during coalbed methane production , 2010 .

[33]  W. P. Diamond,et al.  Numerical analysis of the influence of in-seam horizontal methane drainage boreholes on longwall face emission rates , 2007 .

[34]  Jishan Liu,et al.  Impact of CO2 injection and differential deformation on CO2 injectivity under in-situ stress conditions , 2010 .

[35]  Andreas Busch,et al.  Flue gas and pure CO2 sorption properties of coal: A comparative study , 2006 .

[36]  Zhou Shi.  New Thinking About Exploitation of Coal Seams with High Gas Content and Main Problems to be Researched , 2001 .

[37]  Y. Gensterblum,et al.  High-pressure methane and carbon dioxide adsorption on dry and moisture-equilibrated Pennsylvanian coals , 2002 .

[38]  J. P. Seidle,et al.  Application of Matchstick Geometry To Stress Dependent Permeability in Coals , 1992 .

[39]  Eric P. Robertson,et al.  Modeling Permeability in Coal Using Sorption-Induced Strain Data , 2005 .

[40]  M. Mazzotti,et al.  Enhanced coalbed methane recovery , 2009 .

[41]  Suzanne D. Golding,et al.  Numerical simulation of multicomponent gas diffusion and flow in coals for CO2 enhanced coalbed methane recovery , 2007 .

[42]  Huang Pei-ming,et al.  Simulation of CO2-geosequestration enhanced coal bed methane recovery with a deformation-flow coupled model , 2009 .

[43]  Yu Wu,et al.  Dual poroelastic response of a coal seam to CO2 injection , 2010 .

[44]  C. Özgen Karacan,et al.  Development and application of reservoir models and artificial neural networks for optimizing ventilation air requirements in development mining of coal seams , 2007 .

[45]  M. Biot.  General Theory of Three‐Dimensional Consolidation , 1941 .

[46]  Roger Beckie,et al.  Flow of Coal-Bed Methane to a Gallery , 2000 .

[47]  I. Gray,et al.  Reservoir Engineering in Coal Seams: Part 1-The Physical Process of Gas Storage and Movement in Coal Seams , 1987 .

[48]  Zhou Fubao,et al.  Study on the coexistence of gas and coal spontaneous combustion(I):disaster mechanism , 2012 .

[49]  Baohua Guo,et al.  Improvement of methane drainage in high gassy coal seam using waterjet technique , 2009 .

[50]  Marco Mazzotti,et al.  Measuring and modeling the competitive adsorption of CO2, CH4, and N2 on a dry coal. , 2008, Langmuir : the ACS journal of surfaces and colloids.

[51]  Wang Zhaofeng,et al.  Experimental study on technology of accelerating methane release by nitrogen injection in coalbed , 2010 .

[52]  W. Gunter,et al.  Deep coalbed methane in Alberta, Canada: A fuel resource with the potential of zero greenhouse gas emissions , 1997 .

[53]  Lei Wang,et al.  Environmental impact of coal mine methane emissions and responding strategies in China , 2011 .