J. SE Asian Appl. Geol., 2015, Vol. 7(2), pp. 102–111 NUMERICAL MODELLING AND SIMULATION OF CO 2 –ENHANCED COAL-BED METHANE RECOVERY (CO 2 -ECBMR): THE EFFECT OF COAL SWELLING ON GAS PRODUCTION PERFORMANCE Ferian Anggara * 1 , Kyuro Sasaki 2 , and Yuichi Sugai 2 1 Department of Geological Engineering, Gadjah Mada University, Yogyakarta, Indonesia 2 Department of Earth Resources Engineering, Kyushu University, Fukuoka 819-0395 Japan Abstract This presents study investigate the effect of swelling on gas production performances at coal reser- voirs during CO 2 -ECBMR processes. The stress- dependent permeability-models to express effect of coal matrix shrinkage/swelling using Palmer and Mansoori (P&M) and Shi and Durucan (S&D) models were constructed based on present experi- mental results for typical coal reservoirs with the distance of 400 to 800 m between injection and production wells. By applying the P&M and S&D models, the numerical simulation results showed that CH 4 production rate was decreasing and peak production time was delayed due to effect of stress and permeability changes caused by coal matrix swelling. The total CH 4 production ratio of swelling effect/no-swelling was simulated as 0.18 to 0.95 for permeability 1 to 100 mD, respectively. It has been cleared that swelling affects gas production at per- meability 1 to 15 mD, however, it can be negligible at permeability over 15 mD. Keywords: Coal swelling in CO 2 , Permeability, Low rank coal, CO 2 -ECBMR * Corresponding author: F. ANGGARA, Depart- ment of Geological Engineering, Gadjah Mada Univer- sity. Jl. Grafika 2 Yogyakarta, Indonesia. E-mail: ferian@ugm.ac.id 1 Introduction In regard to simulate the effect of swelling and others factors in field scale, a numeri- cal modelling of CO 2 -ECBMR has been con- structed. The reservoir simulator used for the study was ECLIPSE E300, 2012.1 by Schlum- berger (Schlumberger, 2012) which have incor- porated dual porosity model, sorption and dif- fusion processes, as well as coal shrinkage and compaction effects. A modified Warren and Root model (Warren and Root, 1963) have been used to describe dual porosity process in coal bed methane model. The adsorbed concentra- tion on micro-pore in coal surface is assumed to be a function of pressure only and described by Langmuir isotherm. To accommodate differ- ent gases on CO 2 -ECBMR project, an extended Langmuir isotherm is used to describe the coal sorption for different components. The diffu- sive flow of gas from the matrix to cleat system is given by Fick’s law while from cleat to well be governed by Darcy law. Rock compaction is used to model the compression and expansion of the pore volume and its effect on permeabil- ity. The main objectives of this study was to ex- amine the swelling effect on coal permeability based on stress-dependent permeability model related to gas production. 102