| Through thin section identification, scanning electron microscope observation, inclusion analysis, clay mineral analysis, vitrinite reflectance test, electron probe and carbon and oxygen isotope analysis, combined with the research results of structural evolution history and thermal evolution history of organic matter, the diagenetic environment and evolution model of the clastic reservoir of the Paleogene Pinghu Formation in Xihu Sag are analyzed, and the pore evolution process is restored and the porosity is calculated quantitatively. The clastic reservoir of Pinghu Formation has been in acidic diagenetic environment for a long time, and sometime in acid- alkalinity transitional environment or alkaline environment. The acidic diagenetic environment is marked by dissolution of carbonate minerals, dissolution and alteration of feldspar into kaolinite and associated with secondary enlargement of quartz. The alkaline diagenetic environment is characterized by the dissolution of grains and their secondary enlarged edge of quartz, secondary enlargement of feldspar and precipitation of iron-bearing carbonate minerals. The diagenetic environment of the reservoir in the study area has roughly experienced the evolution process of weak acid—acid—acid-alkalinity transition—alkaline. The pore evolution model of Pinghu Formation is established, which provides a basis for the prediction of high-quality reservoirs in this area. |
