The Accumulation Characteristics of P11 Low-permeability Reservoir in Pinghu Oil and Gas Field, the East China Sea

P11 oil bearing reservoir is mainly consist of lithic arkose quartzose sandstone, which has the characteristics of medium porosity and low permeability. Through the experiments of rock slices, scanning electron microscopy and oil-gas inclusions, the porosity evolution process and oil-gas charging history of the reservoir are established. The results show that the P11 reservoir is a medium cemented and dissolved phase in strong compaction. P11 oil bearing reservoir has experienced two periods of gas-oil charging, and the first period is the primary oil charging process occurring nearly 2-4 Ma ago. Before the oil-gas charging, the reservoir was already in the process of densification, which results in low oil saturation of the P11 layer. The second period of hydrocarbon invaded and fractionated the previous crude oil. Consequently, the disordered gas-oil-water interfaces are formed by the serious anisotropy of the P11 reservoir. The features of deep tight oil or gas reservoirs reveal that it is more difficult to find high-quality reservoirs in Fangheting, and finding local sweets reservoirs and effective development of low-permeability gas have become the focus of late production preservation in oil and gas fields.