Swelling‐induced changes in coal microstructure due to supercritical CO2 injection

Enhanced coalbed methane recovery and CO2 geo-storage in coal seams are severely limited by permeability decrease caused by CO2 injection and associated coal matrix swelling. Typically it is assumed that matrix swelling leads to coal cleat closure and as a consequence, permeability is reduced. However, this assumption has not yet been directly observed. Using a novel in-situ reservoir condition x-ray micro computed tomography flooding apparatus, for the first time we observed such micro cleat closure induced by supercritical CO2 flooding in-situ. Furthermore, fracturing of the mineral phase (embedded in the coal) was observed; this fracturing was induced by the internal swelling stress. We conclude that coal permeability is drastically reduced by cleat closure, which again is caused by coal matrix swelling; which again is caused by flooding with supercritical CO2.

[1]  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 .

[2]  Saikat Mazumder,et al.  Swelling of Coal in Response to CO2 Sequestration for ECBM and Its Effect on Fracture Permeability , 2006 .

[3]  Wenli Song,et al.  Displacement Behavior of Methane Adsorbed on Coal by CO2 Injection , 2011 .

[4]  J. Olson,et al.  Characteristics and origins of coal cleat: A review , 1998 .

[5]  Luke D. Connell,et al.  Influence of the effective stress coefficient and sorption-induced strain on the evolution of coal permeability: Model development and analysis , 2012 .

[6]  P. J. Reucroft,et al.  Gas-induced swelling in coal , 1986 .

[7]  Grant S. Bromhal,et al.  Influence of carbon dioxide on coal permeability determined by pressure transient methods , 2009 .

[8]  L. Connell,et al.  A theoretical model for gas adsorption-induced coal swelling , 2007 .

[9]  S. Iglauer,et al.  Multi-scale x-ray computed tomography analysis of coal microstructure and permeability changes as a function of effective stress , 2016 .

[10]  S. Reeves,et al.  Modeling the Effects of Matrix Shrinkage and Differential Swelling on Coalbed Methane Recovery and Carbon Sequestration , 2003 .

[11]  Jean-Michel Morel,et al.  A non-local algorithm for image denoising , 2005, 2005 IEEE Computer Society Conference on Computer Vision and Pattern Recognition (CVPR'05).

[12]  T. Moore,et al.  Coalbed methane: A review , 2012 .

[13]  S. Durucan,et al.  GHGT-11 Flue gas injection for CO 2 storage and enhanced coalbed methane recovery : Mixed gas sorption and swelling characteristics of coals , 2013 .

[14]  Jos B. T. M. Roerdink,et al.  The Watershed Transform: Definitions, Algorithms and Parallelization Strategies , 2000, Fundam. Informaticae.

[15]  X. Miao,et al.  Evolution of coal permeability: Contribution of heterogeneous swelling processes , 2011 .

[16]  S. Iglauer,et al.  Residual trapping of supercritical CO2 in oil-wet sandstone. , 2016, Journal of colloid and interface science.

[17]  Ahmed Barifcani,et al.  Swelling effect on coal micro structure and associated permeability reduction , 2016 .

[18]  Scott R. Reeves,et al.  The Coal-Seq project: Key results from field, laboratory, and modeling studies , 2005 .

[19]  Guoliang Chen,et al.  Influence of gas production induced volumetric strain on permeability of coal , 1997 .

[20]  Derek Elsworth,et al.  Permeability evolution in fractured coal: The roles of fracture geometry and water-content , 2011 .

[21]  Ghazal Izadi,et al.  Permeability evolution of fluid-infiltrated coal containing discrete fractures , 2011 .

[22]  Sevket Durucan,et al.  A model for changes in coalbed permeability during primary and enhanced methane, recovery , 2005 .

[23]  C. Özgen Karacan,et al.  Heterogeneous Sorption and Swelling in a Confined and Stressed Coal during CO2 Injection , 2003 .

[24]  Jonny Rutqvist,et al.  A New Coal-Permeability Model: Internal Swelling Stress and Fracture–Matrix Interaction , 2010 .

[25]  T. Reuschlé,et al.  Compaction and Failure in High Porosity Carbonates: Mechanical Data and Microstructural Observations , 2009 .

[26]  S. Durucan,et al.  Flue Gas Injection for CO2 Storage and Enhanced Coalbed Methane Recovery : Mixed Gas Sorption and Swelling Characteristics of Coals , 2013 .

[27]  Martin J. Blunt,et al.  Residual CO2 imaged with X‐ray micro‐tomography , 2011 .

[28]  Seyed Nezameddin Ashrafizadeh,et al.  Wettability determination by contact angle measurements: hvbB coal-water system with injection of synthetic flue gas and CO2. , 2011, Journal of colloid and interface science.

[29]  John W. Larsen,et al.  The effects of dissolved CO2 on coal structure and properties , 2004 .

[30]  S. Durucan,et al.  CO2 Storage in Deep Unminable Coal Seams , 2005 .

[31]  W. Wakeham,et al.  The Viscosity of Carbon Dioxide , 1998 .

[32]  Dorthe Wildenschild,et al.  Image processing of multiphase images obtained via X‐ray microtomography: A review , 2014 .

[33]  R. Marc Bustin,et al.  Selective transport of CO2, CH4, and N2 in coals: insights from modeling of experimental gas adsorption data , 2004 .