Abstract:

Abstract: Reservoirs are relatively welldeveloped in the Leikoupo Formation of western Sichuan Depression. They are mainly algal dolorenite and mediumfine crystalline dolostone reservoirs with intergranular and intragranular dissolution pores. The pore structures are dominated by mediumfine pore throat. As a whole, these reservoirs are low in both porosity and permeability. Thick algal dolorenite reservoirs in the Formation distribute widely in western margin of the Basin. As a whole, the reservoirs were formed in seabed burial diagenetic environment. However, the west segment of the Depression shows evidence of meteoric diagenesis which weakens southward. Controlled by different diagenetic enviroments, the reservoirs experienced such diagenetic processes as compaction, pressuresolution, cementation, dissolution, dolomitization, and etc. Among them, the dissolution, dolomitization, and later fracturing are constructive diagenesis. The penecontemporaneous exposure dissolution and hypergene dissolution mainly occurred in northern Zhongba structural belt, while the burial dissolution contributed a lot to the formation of reservoirs in the midsouth segment of the Depression. The oolitic and dolorenite are thought to be mainly related to early back flow seepage and burial dolomitization. A comprehensive study of sedimentation and diagnesis of the Depression indicates that the Leikoupo Formation in the south of the northern segment of the Depression has welldeveloped arenitic shoals and experienced penecontemporaneous meteoric dissolution, hypergene dissolution and burial dissolution, and thus may be the most potential exploration targets. But attention shall also be paid to the middle segment for the fact that bitumen is observed in the intergranular pores of ooliteic and dolorenite there. 

Key words: Key words： reservoir property, digenetic environment, diagenetic type, Leikoupo Formation, Western Sichuan Depression