Genetic Analysis of the Beach Facies Reservoir in Feixianguan Formation in Tieshan,Northeastern Sichuan and Its Peripheral Area

The study adopts macro and micro methods to address the complex origin of beach reservoir in Tieshan and its peripheral area,northeastern Sichuan.The main reservoir space types are moldic,intragranular solution pores,intercrystal pores and residual intergranular pores.The reservoir properties are relatively poor,dominated mainly by secondary pores.while porosity/permeability relationship is not unique,which may be caused by the fissure-pore and pore-fissure types with low porosity and low permeability.The origin of Feixianguan beach reservoir is controlled together by eustatic sea level,tectonism,burial solution.Oolitic beach is distributed along the margin of platform.Due to eustatic cycle,oolitic beach experienced multi-episodic exposures,which was dissolved by atmospheric water.Since porosity and permeability were decreased by compaction and multi-episodic cementation,secondary pores flourished with the burial solution and tectonic fluctuation,which dramatically boosted the reservoir property.