Characteristics and genetic mechanism of salt structure in Fuxingchang anticline, Jiangling Sag, Jianghan Basin

Abstract

The Fuxingchang salt anticline is an important oil-bearing structure in the Jiangling Sag of the Jianghan Basin, while its structural evolution and formation mechanism are unclear, which restricts the delicate exploration of oil and gas. Therefore, the analysis of structural evolution and formation mechanism of the Fuxingchang salt anticline is not only helpful to understand the influence of salt bed flow under different stress backgrounds on the formation and evolution of the anticline, but also important to understand the process of petroleum accumulation. The structural characteristics and genetic mechanism of Fuxingchang anticline were studied by analyzing 3D seismic data and combining with the techniques of balance restoration of key structural layers and growth strata analysis. The results show that the Fuxingchang anticline is a salt anticline with significant structural features that vary along strike, resulting from multiple stages of fault reconstruction and complex deformation mechanisms. The anticline was initially formed during normal faulting in the sedimentary period from Early Eocene Xingouzui Formation to the early period of Late Eocene, which formed roller fold and caused the accumulation of salt layer. From the late period of Late Eocene to Oligocene, the differential loading of sedimentary strata drove salt beds to flow from west to east, resulting in the westward dip of the whole structure and the formation of monoclinal structure, which was uplifted and denudated in the late period of Oligocene. The anticline was finalized from Neogene to Quaternary, and evolved into a compressional salt anticline, associated with reverse faults and kink-band structures. The formation and evolution of Fuxingchang anticline are influenced by the combined effects of regional stress background, salt layer of Shashi Formation, the east-dipping normal faults, sub-salt paleostructures, etc. The structural trap formed by Fuxingchang salt anticline occurred slightly earlier than the main oil expulsion period of source rocks, and during the main oil expulsion period, the structure was in the depression stage, with weak fault activity, which was conducive to the early accumulation of trapped oil and gas.

Keywords

• balanced restoration technique
• evolution characteristics
• formation mechanics
• fuxingchang anticline
• jiangling sag
• jianghan basin