The Effect of Pore Structure on the Distribution of Wet Gases in Coal Seams of Enhong Syncline, SW China

The origin of the high content of wet gases in coalbed seams is very important geologically, especially in the Enhong syncline in China. The present study focuses on the role of the material that generates the hydrocarbons. The effect of the pore structure on the generation of wet gases has not been thoroughly examined. The present paper characterizes the coal pore structure in the “wet gas area” and “dry gas area”. The pore structures in the two areas are shown to have different features, which affect the distribution of the wet gases. With respect to the pore structure parameters, coals in the wet gas area have a greater total specific surface area and pore volume in micropores. The pore structure types also differ between the two areas: the pore structures in the dry gas areas are mainly of the parallel type and reverse S type, which is favorable for the migration and dissipation of coalbed gases. The pore structure in the wet gas area is relatively closed, with poor connectivity and susceptibility to blockage. The micropore volume, total specific surface area, and the connectivity of the pore structure significantly affect the reserve of wet gases. The adsorption capacity of the micropores and the closed pore structure contribute to the preservation of wet gases.