Characteristics of Oil and Gas Produced by In Situ Heating of Shale: A Case Study of the Chang 7 Member, Ordos Basin, China

Shale in the Chang 7 member of the Triassic Yanchang Formation of Ordos Basin is just suitable to shale oil development by in situ heating for its low maturity. In this study, continuous in situ heating simulations at three different heating rates were undertaken to investigate oil and gas characteristics of the Chang 7 shale. Results indicated that the shale has an oil production potential of up to 43-44 kg/t shale when heated to 450 degrees C. The heating rate had a minor effect on oil yield. The produced oil was light oil with a C-8 - C-10 main peak. Saturated and aromatic hydrocarbons took up a total proportion of 87-90%. The saturated hydrocarbon contents in produced oil decreased with the increasing temperature accompanying aromatic increasing. Total gas yields for the three heating rates after heating to 450 degrees C were not significantly different, with total yields of 15.68-16.68 m(3)/t shale. However, yields of different gas components varied with the heating rate. The yield of hydrocarbon gas at a fixed temperature increased with the decreasing heating rate. Our experimental results also indicated that slow heating was favorable to reduce harmful gas formation by an in situ heating method during Chang 7 shale oil development.