Effect of Diagenesis on Reservoir Distribution in a Sequence Strati-graphic Framework: Evidence from the Feixianguan Formation (Triassic) in Tieshan District of Northeastern Sichuan, China

Abstract

Abstract. By integrating diagenesis and sequence stratigraphy, the effect of sedimentary-diagenetic reformation on reservoir quality and distribution was investigated with in a sequence stratigraphic framework. Based on the petrological characteristics, sedimentary microfacies and logs analysis, 2 third-order sequences and 5 system tracts are distinguished in the Feixianguan Formation, as well as a stratigraphic framework has been established. Besides, the diagenetic processes of Feixianguan Formation contain compaction, pressure-solution, cementation, dolomitization and dissolution. A analysis reveals that cementation is the major cause of porosity-loss for primary and secondary porosity. Contrary to the adverse impact of cementation on reservoir space, polygenetic dolomitization and dissolution greatly improve the carbonate rocks reservoir and permeability. Sequence stratigraphic framework constrains the distribution of diagenesis, which result that dolomitization is most evident in transgressive system tract (TST) and below maximum flooding surfaces (MFS) in Sq1, and locally occur in lower part of the highstand system tract (HST). And it is also proved that the dolomitic reservoir shows high porosity in TST of Sq1 and moderate quality in HST of Sq1.