The source-sink system and its control on large-area lithologic reservoirs of the lower Minghuazhen Formation in the southern Bohai Sea

Abstract

In recent years, a large number of large-area sand bodies have been drilled in the Neogene in the southern Bohai Sea, and several 100-million-ton oilfields have been discovered, indicating that the lower member of the Minghuazhen Formation has enormous exploration potential. The source-sink elements of the development of such sand bodies are unclear, which seriously restricts the exploration of lithologic reservoirs in the lower member of the Minghuazhen Formation. Using paleontology, heavy minerals, seismic, drilling and other data, this paper explores the source-sink system and its control on large-area lithologic reservoirs in the lower member of the Minghuazhen Formation of the southern Bohai Sea. The results show that: The Yanshan-Liaoxi uplift, the Liaodong uplift, the Luxi uplift and the Jiaodong uplift mainly develop source-sink systems in four directions in the study area’s lower member of the Minghuazhen Formation. Next, the Luxi uplift and the Jiaodong uplift are relatively close. The Luxi uplift and the Liaodong uplift significantly impact the source-sink system in the study area’s lower part of the Minghuazhen Formation. In contrast, the Yanshan-Liaoxi uplift has a weaker impact on the source-sink system. Three sedimentary systems, including rivers, river-lake interactions and lakes, are mainly developed in the study area’s lower member of the Minghuazhen Formation. Among them, the sand bodies formed by river-lake interactions and lake shallow water deltas are larger. The study area’s lower member of the Minghuazhen Formation has favorable source-sink conditions for creating large-scale sand bodies. Among them, temperate-subtropical climate, sufficient rainfall, developed paleo-water system, felsic metamorphic rocks and magmatic parent rocks, and frequent expansion and shrinkage of lakes are beneficial to the development of large-area sand bodies. The connection of channel sand–sheet sand–channel sand leads to the development of large-scale lithologic traps in the study area’s lower member of the Minghuazhen Formation. Compared with channel sand alone, river-lake interactions and shallow water deltas have the potential to form large-area lithologic reservoirs. This understanding can help explore large Neogene oil and gas reservoirs in the Bohai Sea.

Keywords

• source-sink system
• large-area sand body
• lithologic trap
• lithologic reservoir
• the lower member of the minghuazhen formation
• southern bohai sea