Effect of lithofacies on shale reservoir and hydrocarbon bearing capacity in the Shahejie Formation, Zhanhua Sag, eastern China

Abstract

By using microscope, nuclear magnetic resonance (NMR), hydrocarbon generation and expulsion and nitrogen adsorption, reservoir properties and oil-gas bearing capacity of different shale lithofacies were examined with the continental shale of Zhanhua Sag in the Jiyang Depression of the Bohai Bay Basin as the examples. The results showed that the organic-rich laminar lithofacies have the best oil and gas bearing properties, while the organic-rich layer lithofacies take second place. The laminar lithofacies mainly developed mesopores and macropores, even microcracks, and the porosity connectivity is better than that of the layer lithofacies. The micropores and mesopores are mainly developed in the layer lithofacies, so the reservoir space is small. Therefore, the lithofacies with laminar not only increases the storage space of reservoir but also can improve the mobility of oil and gas. By the actual oil production comparison of different lithofacies, the hydrocarbon generation quantity of the organic-rich lithofacies is 336.68t, otherwise, the organic-contain lithofacies only 40.49t. Therefore, the organic-rich laminar lithofacies have the best oil production effect and can be used as a favorable target for oil and gas exploration in shale.