Kinetics of early methane generation from Green River shale

Abstract

During oil/gas exploration in an area, there is a question as to whether methane in the strata was generatedin situ mainly by thermal degradation of local organic matter. The key to the question is whether the kerogen could produce methane of more than 80 mL/g TOC, when its R_o increased from initial (0.36%) to current value of 0.70% during thermal evolution. The authors have made efforts to answer this question by the kinetics method. First, a series of pyrolysis experiments were carried out to obtain data of methane yield and R_o evolution, from which kinetic parameters of methane and R_o were derived; then these parameters were extrapolated to the geological condition and finally, a methane yield, 96 mL/g TOC, was predicted. The result suggests that from the view of hydrocarbon generation, methane in the seam should be from thermal degradation of local kerogen.