Diagenetic Reservoir Facies and Diagenetic Evolutionary Sequences of Extra-Low Permeability Reservoir in the Upper Triassic Xujiahe Formation of Fenggu Structure, Western Sichuan Depression, China

Abstract: Diagenetic reservoir facies are the integration of some diagenesis and special reservoir spaces to describe reservoir properties. It is critical for predicting the distribution of high-quality reservoir to analyze the evolutionary processes and sequences of different diagenetic reservoir facies and to explore reservoir forming mechanism. This study focuses on reservoir in the Upper Triassic Xujiahe Formation in Fenggu Structure of Western Sichuan Depression. They are buried deeply and classified as low porosity and extra-low permeability reservoir. After divided diagenesis stages, researched the diagenetic reservoir facies types and diagenetic evolutionary sequences based on the analysis of petrologic characteristic, sedimentary facies, diagenetic types, apparent compacting rate, apparent cementing rate, combination of reservoir spaces, porosity, permeability and some other parameters. The diagenetic reservoir facies are divided into 4 types, namely as, 1st, the residual intergranular pores-dissolved pores diagenetic reservoir facies with weak compaction and strong dissolution, 2nd, the dissolved pores diagenetic reservoir facies with compaction and dissolution, 3rd, the dissolved pores- microporosity diagenetic reservoir facies with middle to strong compaction and weak dissolution and 4th, the tight diagenetic reservoir facies with strong dissolution. The development of the relic primary intergranular pores and secondary dissolution pores is mainly controlled by the rock components, compaction of pores, the filling of authigenic minerals and the multi-stages dissolution and the injection of acid fluid. The effective diagenetic reservoir facies of the 4 types are respectively the residual intergranular pores-dissolved pores diagenetic reservoir facies with weak compaction and strong dissolution and the dissolved pores diagenetic reservoir facies with compaction and dissolution. They play an important role in the formation of the high-quality reservoir of Xujiahe Formation.

AAPG Search and Discovery Article #90142 © 2012 AAPG Annual Convention and Exhibition, April 22-25, 2012, Long Beach, California