Numerical simulation of CO2 enhanced coal bed methane recovery for a Vietnamese coal seam

Abstract

A CO2-ECBMR numerical modeling has been build for the Mao Khe coal seam in Vietnam. The numerical simulations for sensitivity studies on the dominant factors for CH4 production, such as permeability, CO2 injection rate and well spacing have been carried out by giving CO2 and CH4 adsorption capacities and viscocities of CO2 and water as a function of the coal seam temperature (40 to 65 °C). Finally, the numerical simulations with fivespot model have been presented to evaluate CO2 injectivity and CH4 productivity by changing the well spacing. The results show that CO2 injection is roughly proportional to number of injectors, however the time of the maximum CH4 production rate is delayed with 5-spots unit area. From view of economical evaluation, drilling cost of wells and well spacing are important parameters to decide the optimum production scheme. (Received May 6, 2010; accepted September 6, 2010)