Abstract: The reservoir of Meishan Formation in Ledong-Lingshui sag has become a research hotspot, and the study of diagenetic period and reservoir pore evolution in a high-temperature overpressure environment is extremely important in Qiongdongnan basin. In this paper, the diagenesis of Meishan Formation reservoir in Ledong-Lingshui sag was studied by synthesizing the data of thin sections, scanning electron microscopes, reservoir physical properties, carbon and oxygen isotopes, and clay X-diffraction, so as to determine the diagenetic symbiosis sequence and establish the pore evolution model. The results show that the reservoirs of Meishan Formation in Ledong-Lingshui sag have undergone various diagenesis processes such as compaction, cementation and dissolution, and the diagenetic sequences are as follows: early clay cementation→ calcite cementation→ feldspar, carbonate dissolution→ quartz increase, authigenic quartz particles→ iron calcite, iron dolomite cementation→ first-phase oil and gas charging→feldspar, carbonate mineral dissolution→ second-phase oil and gas charging. Under the influence of high temperature and overpressure, the development of cementation is inhibited and the dissolution porosity of diagenetic fluid is improved. The overall porosity increases due to the high temperature and remains unchanged under overpressure.

Key words: reservoir diagenesis, overpressure, pore evolution, deep water, Meishan Formation, Qiongdongnan basin