Multi-source hydrocarbon accumulation in the faulted and deeply depressed Tangdong area, Qikou Sag, Bohai Bay Basin

Le résumé fourni par la source

Based on organic geochemical analysis data, this study examined the characteristics of multi-source hydrocarbon accumulation in the Tangdong area of Qikou Depression, Bohai Bay Basin. The results indicate that the Tangdong area contains four source rock sequences: the third member of the Dongying Formation (E d 3 ), the middle and lower sub-members of the first and third member of Shahejie Formation (E s 1M , E s 1L , E s 3 ). Both the salinity of sedimentary water bodies and the contribution of bacteria in the four source rock sequences gradual increase in the order of E s 3 , E s 1M , E s 1L and E d 3 , as indicated by the Ga/C 30 H, ETR , sterane/C 30 hopane, C 24 TeT/C 26 TT, C 23 TT/C 30 H, and the carbon isotope data of group components. Additionally, certain quantities of 4-methylsterane have been detected in source rocks in the E s 3 , E s 1M , and E d 3 , suggesting the special contribution of dinoflagellates to these source rocks. Based on biomarker parameters and carbon isotope data, the crude oil can be categorized into classes A to D, which show complex multi-source accumulation characterized by different sources in the same well and even in the same layer. Class A crude oil occurring in the higher part of the E d 3 originates from source rocks in the E s 1 L and E s 3 . Class B oil existing in the lower part of the E d 3 is derived from source rocks in the Ed 3 . Class C oil found in the E s 1U is sourced from source rocks in the E s 1M . Class D oil present in the E s 1L is contributed indigenously by the source rocks in the E s 1L , establishing this unit as a lithologic hydrocarbon reservoir with source rocks and reservoirs in the same layer. Under the guidance of the understanding of multi-source hydrocarbon accumulation, currently, three wells have been drilled, all yielding satisfactory outcomes. • Deep-sag E s 3 and E s 1 source rocks identified, expanding traditional source rock models. • Evidence supports E s 3 deep-sag lithologic reservoirs as self-sourced and self-sealed. • Deep-sag crude oils in E s 3 originate from local source rocks, confirming in-situ generation. • Multi-source accumulation patterns in deep sag enhance understanding of charge systems.

Ce résumé expose les affirmations des auteurs. BNTIC ne l’interprète pas comme une validation indépendante des résultats.