Abstract: This study focuses on the pore evolution during the diagenetic period of the Yingshan Formation in the Gucheng region in the Tarim Basin. Specifically, the petrophysical characteristics, diagenetic effect, and reservoir characteristics of the target layers are investigated based on the analysis of core description, flake identification, cathodoluminescence, well logging data, and geochemical data. The results show that reservoir rocks of Yingshan Formation in Gucheng region are primarily composed of limestone and dolomite. Of which, the dolomite is mostly distributed in the lower section of the Yingshan Formation. Furthermore, the fine grained automorphic-semi-automorphic dolomite and medium-coarse crystalline dolomite both exhibit relatively good porosity. The reservoir space is mainly made up of intercrystalline pores, intercrystalline pores and cracks, which forms three types of reservoirs including the crack type, pore type, and crack-hole type reservoirs. The diagenetic effect has a significant impact on the storing performance of the reservoir in the research region. In particular, the early cementation, compaction and pressure dissolution, silicidation, and filling of hydrothermal minerals have a destructive effect on the primary pores. The dolomitization, rupture, and hydrothermal dissolution in the shallow burial are constructive diagenetic effects. Affected by the transitional dolomitization, the intercrystalline pores in dolomites exhibit a low degree of development. The hydrothermal dissolution effect plays a key role in the formation of high-quality reservoir.

Key words: Tarim Basin, Gucheng region, Yingshan Formation, diagenetic effects, reservoir characteristics, pore evolution