Characteristics and controlling factors of natural gas source rocks of Middle Permian Gufeng Formation in western part of Lower Yangtze Platform, China

Unconventional natural gas resources in the Lower Yangtze region have caused plenty of interests of the Chinese energy companies in recent years. The developing characteristics and controlling factors of natural gas source rocks in the Middle Permian Gufeng Formation were studied by analyzing the typical field profiles and boreholes. The thickness center of Gufeng Formation shale locates in the Wuhu area, and the maximum of thickness is greater than 150 m. The total organic carbon (TOC) content of shale is relatively high, mainly ranging from 1.0% to 4.0%, with an average value of about 3.4%, and there are significant differences for the TOC content of different systematic tracts. Kerogens are mainly of types Ⅱ₂ and Ⅲ. The Gufeng Formation shale is in the late stage of thermal maturity, and within the range of the dry gas window. The development of organic-rich beds in the Gufeng Formation was related to volcanism and its closely associated hydrothermal fluid activities. Volcanism and hydrothermal fluid activities brought materials from deep earth to surface, which enriched water body with nutrient-rich elements, caused biological bloom and formed high productivity, thus provided a good material for good source rocks.