Sedimentary Facies Of The Xixiangchi Group In The Southeastern Sichuan Basin And Its Relationship With Reservoirs

In this paper,Xixiangchi formation in southeast of Sichuani area as the research object,carbonate sedimentology outcrop,carbonate reservoir geology as the theoretical guidance,based on a large number of literature investigation,combination with drill core and thin section observations?logging data and kinds of analyses or test materials,this paper have studied the strara,sedimentary facies,reservoir type and characteristics,in southeast Sichuan area,elaborate the main controlling factors of reservoir development,established the main reservoir evolution model,forecast the favorable block of reservoir distribution.The studies of formation show that top and bottom boundaries of strara clear,the layers of the top of Xixiangchi formation have contacted with the layers of the bottom of the overlying Tongzi formation and underlying Gaotai formation as the conformity,the formation is thinning from east to west.Based on a variety of sedimentary facies signs and take the depositional setting for Sichuan basin at Xixiangchi age into consideration,it is believed that Xixiangchi formation in southeast Sichuan area belongs to restricted platform facies,which based on the hydrodynamic conditions and depositional characteristics,can be subdivided into restricted plate,intraplateform,lagoon subfacies and beach-core,beach-wing,inter-beach,and dolomitic lagoon microfacies,wherein beach-core microfacies are the most favorable facies belt for reservoir development,with dolomitic lagoon microfacies next to it.The research of reservoir holds that reservoirs of Xixiangchi formation in southeast of Sichuan area are seen in both the upper and lower member.Grain dolomite is the main component of reservoir rock with crystalline dolomite next to it.Interparticle dissolution pore and intercrystal pores are the main reservoir space,and the main percolation space is the crack.Most of the reservoirs belong to category II and III,and most of them belong to crack-pore type reservoirs with medium pore or medium percolation.A combined effect of deposition,diagenesis and tectonism controls the final distribution characteristics and degree of development for reservoirs.As it is concluded from above analysis,this paper holds that the the sandy beach microfacise and oolitic beach microfacies are conducive to the development of the reservoirs,and the dolomitic lagoon following.The former is mainly distributed in the place from Shizhushuangliuba,Dingshan-1,Xishuiliangcun,Lin-1,the latter are widely distributed in study area,but the differences between each wellblock are great.