Analysis of Differential Oil and Gas Migration by Fault and Hydrocarbon Accumulation Controlling Factors in Bozhong A Area of Bohai Sea

Bozhong A area is located in the northern slope of Bonan low uplift in Bohai Sea, and the main exploration targets were buried hill and Paleocene in the early exploration period. In recent years, the hydrocarbon bearing conditions of Neocene has attracted great attentions. Through study on the hydrocarbon transformation systems, it has been made clear that hydrocarbon vertical migration through faults is the key factor for hydrocarbon accumulation in the Neocene. Based on analyzing results of fault patterns and activity, it has been concluded that back shaped negative flower structure and fault activity controlled the differential oil and gas accumulation, indicating structural ridges might be the beneficial direction of oil and gas migration. Furthermore, with fractal geometry principle, the fractal feature in the study area has been studied. The fractal dimension value of faults is high in the structural ridges, indicating that hydrocarbon migration efficiency is high in the structural ridges, which confirmed the results from conventional method by semi-quantitative or quantitative evaluation. Recent drilling results in structural ridge had excellent finding of oil and gas bearing layers in Neocene, demonstrating the analyzing results of fault migration mentioned above.