The methane sorption capacity of Paleozoic shales from the Sichuan Basin, China

The methane sorption capacities of Paleozoic shales from the Sichuan Basin were investigated. The primary results show they have sorption capacities ranging between 0.94 and 4.29 cm3/gRock at STP, comparable to the sorption capacity (1.27–2.41 cm3/gRock at STP) of Barnett shale. However, the sorption isotherms indicate that most of the Sichuan Basin shales would reach their approximate sorption equilibrium at 3–4 MPa, in contrast to the continuously upward trend of North American shales. A general positive relationship between TOC content and methane sorption capacity indicates that TOC content is the major controlling factor for the methane sorption of the Sichuan shales. A negative relationship between the clay mineral content and the sorption capacity of these shales may suggest that clay minerals play an insignificant role in the methane sorption of these Paleozoic shales. Sorption capacities and variation ranges are generally ordered as to geological age, viz Cambrian < Silurian < Permian.