Controls on Gas Content and Carbon Isotopic Abundance of Methane in Qinnan-East Coal Bed Methane Block, Qinshui Basin, China

Abstract

Qinnan-East Block is one newly planned coal bed methane (CBM) exploration area in the Qinshui Basin, China, and research on the accumulation of gas in this block is quite limited. In this study, on the basis of a series of laboratory experiments and the latest exploration data, the gas content and carbon isotopic ratio of methane [δ13C(CH4)] in the No. 3 coal seam of Permian Shanxi Formation in Qinnan-East Block were investigated, and then the correlations between δ13C(CH4) and vitrinite reflectance, burial depth, gas content, reservoir pressure, and gas adsorption saturation were analyzed; then, the mechanism controlling the gas bearing properties and the distribution of δ13C(CH4) in the study area were addressed. It turns out that the gas content in the study area ranges from 2.87 to 24.63 m3/t with an average of 13.78 m3/t, the CBM reservoir pressure ranges from 0.86 to 5.96 MPa with an average of 3.09 MPa, the reservoir pressure gradient ranges from 0.11 to 1.06 MPa/100 m with an average of 0.49 MPa/1...