Abstract:

The Pre-caspian Basin is typically characterized by hydrocarbon accumulation in two salt-related sequences, i.e., the
post-salt and pre-salt sequences divided by the Lower Permian Kungurian Group. To improve the understanding of the regularities of hydrocarbon accumulation and provide exploration stratedy data, this paper studies the structural characteristics and controlling factors of hydrocarbon accumulation in the two post- and pre-salt sequences by using the latest data of drilling, seismic section interpretation and structural mapping. Results show that large-scale paleo-uplift and slope were developed in the Paleozoic pre-salt sequence and the Hercynian weathering and leaching greatly improved carbonate reservoir properties. Reef, shoal and karst controlled hydrocarbon accumulation. In contrast, the Lower Permian post-salt sequence was significantly controlled by the lower Permian Kungurian tectonic movement, leading to the formation of different types of traps, such as salt diapir, salt eave, stratigraphic pinchout and sandstone lens body. The highly-efficient salt windows, salt flanks and fractures are the key factors controlling hydrocarbon migration. Favorable match between salt tectonic activity and peak hydrocarbon expulsion of source rock is necessary for hydrocarbon accumulation.

Key words: salt, Permian, hydrocarbon accumulation, structural deformation, Pre-caspian Basin