Enhanced Coalbed Methane Recovery with Respect to Physical Properties of Coal and Operational Parameters

Modelling desorption-controlled reservoirs is a difficult matter owing to the complex nature of hydrocarbon transport processes. The complexity of enhanced coalbed methane (ECBM) recovery is not only caused by desorption-control led behaviour of coalbed reservoirs, but also the interaction between coal media and the injected CO(2)/N(2) gas mixture, which changes the coal properties with respect to injection time. In addition, the characterization of coal reservoirs and the determination of in situ coal properties related to the transport mechanism of methane are complicated, as there is a lack of standard procedures in the literature. In considering these difficulties, this study took the approach that relationships between rank and physical properties of coal be used for evaluation purposes. Parametric simulation studies with rank classification provided more representative results for coal reservoirs rather than univariate analysis. Besides coal rank, simulation cases were run for different reservoir types, well patterns, molar compositions of injected fluid and well types. The shrinkage/swelling process was taken into account by making use of the extended Palmer/Mansoori model. As a result, ECBM recovery was studied in field-scale with rank-dependent coal properties and different operational parameters in order to provide an overview.