The development model for high quality magmatic basement reservoir in a depression of East China Sea

Cores, thin sections, mercury injection data and well logging reservoir properties are adopted for research of the characteristics of basement reservoir in order to explore the high quality hydrocarbon accumulation in the Pingbei region. It is revealed that granite is the best bedrock reservoir in the region. Structural fractures, corrosion fractures and corrosion holes provided most of the reservoir space, among which, structural fractures account for 61%. Granite reservoirs in the study area could be described with the model of typeⅠ. In general, it is funnel-like in shape. The upper part is rather dense because fractures and dissolution holes are filled by the deposits of later stage, and the reservoir physical properties are poor. The middle part of the granite, however, is abundant in fractures and has excellent reservoir space and pore throat conditions by leaching and tectonic stress. The lower part becomes dense again with weak leaching by atmospheric fresh water and little influence by tectonic stress. It is believed that high quality buried basement-hill reservoir should be located in the middle and upper part of the buried hill owing to strong leaching of faults and ruptures by atmospheric fresh water.