Reservoir-forming rules and main controlling factors of Archean buried hill reservoir of middle to northern Liaoxi Uplift in Liaodong Bay area in Bohai Bay Basin

The Bohai Bay Basin is one of the key areas for the exploration of buried hill oil and gas resources in China. In order to create a new prospect for the exploration of the Archaean buried hills in this area, the reservoir-forming laws and main controlling factors of the Archaean buried hill reservoir in the Liaodong Bay area were studied. Based on drilling data such as stratum, logging, and seismic data, this paper classified the lithology and distribution patterns of Archean buried hills in the Liaodong Bay area, and analyzed the dominant reservoir space types and controlling factors. The results show that the Archean buried hills in the Liaodong Bay area are composed of schist, metamorphic granite and cataclastic rocks, with schist being the predominant lithology. The current structure is high in the south and low in the north. The strata are relatively intact in the north, while the upper part of the strata in the south shows evidence of denudation. The proportion of igneous rocks increases gradually from north to south. The metamorphic rocks are dominated by fracture reservoirs. The content of mafic minerals is inversely correlated with the brittleness of rocks. Tectonic deformation led to fracture development. Three sets of structural fractures were developed in the Archean buried hills of the Bohai Bay Basin, i.e., NNE shear fractures and SN tensile fractures were developed in the stress directions of NE strong shear and SN strong compression in the early Yanshanian period, NE shear fractures and NE tensile fractures were developed in the stress directions of NW strong extension and NE weak shear in the early Himalayan period, and EW tensile fractures and NE and NW conjugate shear fractures were developed in the stress directions of NE strong shear and NW weak extension in the late Himalayan period. The degree of regional tectonic activity controlled the effectiveness of the fractures. The Yanshanian movement was the main stage of fracture formation in metamorphic rock reservoirs. During the Himalayan period, fractures were mainly filled and semi-filled with calcite, and effective fractures could be formed through dissolution in the later stage.