Thermal simulation experiment study of the hydrocarbon generation characteristics of low maturity shale

This paper analyzes the hydrocarbon generation and pyrolysis parameters by altering maturity of the shale samples through an autoclave thermal simulation experiment. Research shows that as the temperature increases, Ro can be divided into three stages, namely the slow, medium and rapid increase stages. As Ro increases, gaseous hydrocarbon production rate increases throughout while liquid hydrocarbon production rate decreases in the late stage. Pyrolysis hydrocarbon (S2) content is reduced rapidly as liquid hydrocarbons transform into gaseous hydrocarbons, but the amount of total hydrocarbons actually increases. When Ro reaches 0.65% and 1.0% approximately, there are two hydrocarbon generation peaks. This reflects three stages in the evolution of hydrocarbon generation of the low mature shale, i. e., the initial thermal degradation stage, thermal degradation-thermal cracking stage and thermal cracking stage. The relationship between Ro and total hydrocarbon production rate is an exponential curve, correlating roughly with thermal maturity according to the doublet peak of hydrocarbon generation. The research therefore determines the lower limit of Ro for the prospecting and favorable areas of shale gas in the continental basins of China to be 0.65% and 1.0%, respectively. © 2017, Editorial Office of Earth Science Frontiers. All right reserved.