Organic Geochemistry and Hydrocarbon Generation Characteristics of Shale of the Fourth Member of Yingcheng Formation in the South Shuangcheng Fault Depression, Songliao Basin

In order to evaluate the potential for oil and gas resources in the deep fault depression of the Northern Songliao Basin, shale from the fourth member of the Yingcheng Formation (K1yc4) in the South Shuangcheng Fault Depression was selected as an example. The organic geochemical characteristics such as abundance, type and maturity from experiments on low-maturity source rock samples, the hydrocarbon generation conversion rate, hydrocarbon generation amount and hydrocarbon generation period of the shale from K1yc4 were evaluated via the chemical kinetics method. The hydrocarbon generation threshold of shale from K1yc4 in the South Shuangcheng Fault Depression was analyzed by examining the organic matter (OM) in shale core samples from K1yc4. Based on the thermal simulations to an approximate buried depth of 750 m, the maximum oil-generation stage corresponds to an approximate buried depth of 1380 m. The amounts of generated oil and gas from the shale in K1yc4 are approximately 2.417 × 108 t and 0.546 × 1011 m3, respectively. The shale in K1yc4 generated crude oil mainly during the sedimentary period of the Qingshankou Formation, Yaojia Formation and Nenjiang Formation, and mainly generated natural gas during the sedimentary period of the Nenjiang Formation. In the South Shuangcheng Fault Depression, the high parts of the local structure are the favorable areas for oil and gas exploration of K1yc4 in the sag zone, which could be used for the combined production of shale oil, tight sandstone oil and conventional oil.