Abstract:
Many sets of source rocks and oil-bearing series are widely developed in continental fault basins, and the process of oil and gas accumulation is very complex. Improving the understanding of the process of oil and gas accumulation will help accelerate the process of oil and gas exploration and improve the effectiveness of exploration in such basins. This study focuses on the phenomenon of differential distribution of oil and gas in Bonan Depression. By comprehensively applying previous study results, geological and geochemical data, and inclusion data, the generation, migration, filling, and accumulation of oil and gas in Bonan Depression are systematically analyzed, and the distribution characteristics of oil and gas in different structural zones and their sequential reservoir formation processes are clarified. The study shows that except for the two stages of oil and gas filling in the Sha-4 member of Bonan deep depression zone, there is only one stage of oil and gas filling in other zones and layers. Bonan deep depression zone is the first to be filled, starting from Dongying Formation period (28~25 Ma ago), while the northern steep slope zone is filled with oil and gas relatively late, mainly since the middle stage of the Minghuazhen Formation (3~0 Ma ago). This study finds out that the orderly change of the key elements, including effective source rock distribution and evolution, the type of the transport system and the space distance of the trap-source, controls the order of the reservoir forming process and thus controls the differential distribution of oil and gas. This understanding and conclusion has important guiding significance for the selection of exploration block in fault basins.