Abstract:

In order to reveal the characteristics and genesis mechanism of the deep reservoir in Lufeng sag of Pearl River Mouth basin, this study systematically analyzed the influence of sedimentary environment, abnormal pressure, geothermal gradient, and hydrocarbons charging on the anti-compaction ability of reservoir. The results show that the Paleogene reservoirs with a buried depth of more than 4 000 m in Lufeng sag are still featured by primary pores. The mineral composition of the reservoir is mainly quartz sandstone, and the overall performance is low-medium permeability reservoir. The underwater distributary channel of braided river delta has stable flow action. The long distance transport makes the grain size distribution of rock more uniform and the integral number of mixed matrix less, which are favorable conditions for the development of primary pores. The abnormal pressure formed by mudstone undercompaction transferred to sandstone reservoir can effectively reduce the damage of compaction to pore space. The plasticity and ductility of rock are relatively weak under low geothermal gradient, which slows down the compaction rate of rock. In addition, the oil and gas generated from the source rocks of the fourth member of Wenchang Formation occupied the reservoir space after entering the reservoir, which effectively inhibited the damage of the later compaction and cementation to the reservoir pores. Under the coupling control of four controlling factors, the primary pores of deep reservoir in Lufeng sag are widely developed.

Key words: Lufeng sag, Enping Formation, Wenchang Formation, primary pores, preservation mechanism