Abstract:  Lower Paleozoic carbonate buried hill is an important oil and gas exploration field in Bohai Bay basin. The existing buried hill is mainly concentrated in the high structural position. The reservoir development and hydrocarbon accumulation scale in the low structural position of low slope carbonate buried hill are less understood. In order to understand the developing principles of slope carbonate buried hill and the forming conditions of hydrocarbon accumulations, the tectonic evolution of buried hill, the genetic mechanism of reservoir spaces, the comprehensive analysis of hydrocarbon accumulation were carried out in northwest Shaleitian. It is concluded that: 1) The lithology of the lower Paleozoic buried hill in the slope belt of northwest Shaleitian is composed of the upper association (large set of limestone and muddy limestone) and the lower association (oolitic limestone, interbedded limestone and mudstone), the stable mudstone in the Gushan Formation is the boundary between these two units. 2) The buried hill in the slope zone have undergone five periods of tectonic movements, namely the Indosinian, the Early Yanshanian, the Middle Yanshanian, the Late Yanshanian, and the Xishanian, and had the characteristics of seesaw-type structural evolution. A large number of fractures formed by multi-stage tectonic activities is favorable for the foundation of reservoirs. The component coupling of dominant lithology, superposition stress fracture formation and multi-stage karst transformation controlled the development of carbonate buried hill reservoirs, forming stratiform fracture-soluble high-quality reservoirs, of which the upper association is the dominant oil-gas accumulation layer. 3) The low-slope carbonate buried hill is located in the transitional zone, with the oil-gas accumulation model of upper supergene karst reservoir-lower dense layer shielding and sealing formation, forming large and medium-sized oilfield groups in the slope area.

Key words:  , carbonate rock, slope type buried hill, fracture-soluble reservoir, stratigraphic lateral sealing, Oil-gas accumulation,  , Bohai Sea