Prediction of Favourable Hydrocarbon Transport Pathways of the Jiuzhou Fault in Langgu Sag, Bohai Bay Basin

Abstract

The Jiuzhou fault in the Langgu Sag of the Bohai Bay Basin is a significant oil-source fault that connects source rocks and reservoirs, and thus it can transport oil and gas during the hydrocarbon accumulation period. The hydrocarbon distribution characteristics along the strike of the Jiuzhou fault differ distinctly, indicating that the transport capacity in different fault segments is also different. In this study, we focused on analyzing the fault development characteristics to accurately predict the location of favorable hydrocarbon transport pathways on the Jiuzhou fault. We found that the zones superimposed by paleo relay ramps developed before hydrocarbon accumulation, active faulting areas during hydrocarbon accumulation, and transport ridges of the fault are favourable along-fault locations for transporting hydrocarbons. Based on this idea and 3D seismic data, we investigated the distribution of the paleo relay ramps of the Jiuzhou fault and the fault activity rate during hydrocarbon accumulation using the maximum throw subtraction method. Then, the burial depth contour was employed to search hydrocarbon transport ridges of the fault and therefore predict the location of favourable hydrocarbon transport pathways of the Jiuzhou fault. The prediction results show that there are totally 4 favorable hydrocarbon transport pathways, where hydrocarbons are more likely to migrate vertically and finally accumulate in the overlying formations. In addition, the pathway locations of the Jiuzhou fault are consistent with the hydrocarbon distribution in the study area, demonstrating that this method is reliable and feasible for predicting the favorable hydrocarbon transport pathways of oil-source faults.