A Method for the Prediction of Favorable Sites on Faults That Adjust Outside-of-Source Hydrocarbon Accumulations to High-Slope Areas: A Case of the Zhaobei Fault in Qikou Sag, Bohai Bay Basin, Eastern China

Abstract

In order to study the distribution pattern of hydrocarbons in the shallow layer of the slope area outside of the source in the hydrocarbon-bearing basin, we built a method to predict the favorable site of the fault that adjusts hydrocarbon to the shallow layer in the slope area outside of the source based on the investigation of the mechanism of hydrocarbon adjustment along a conduit fault to a shallow layer. The predicted favorable site is found to be the overlapping area of three sites: the locations of the sand carrier with a lateral supply of hydrocarbon, the transport sites of conduit faults, and the hydrocarbon leakage parts of overlying regional mudstone seal rock. We applied the method in a case study of the favorable sites of the Zhaobei Fault that adjust the hydrocarbon from the lower sub-member within the first member of Shahejie Formation (Es1L) to the shallow Guantao Formation in the Qikou Sag of Bohai Bay Basin. Our prediction shows that the favorable sites are mostly located in the middle part of the Zhaobei Fault with very limited distribution in the east, which are conducive to the oil and gas supplied by the underlying sand carrier in the Es1L Formation to convergence and accumulation in the shallow Guantao Formation. This result is consistent with the distribution of the hydrocarbon in the Guantao Formation located in the middle parts of the Zhaobei Fault, proving that this method is feasible for the prediction of the favorable sites of the fault that adjust hydrocarbon to the shallow layer in the slope area outside of source.