The Evaluation For Carbonate Reservoir Of Member 3 Of Feixianguan Formation Of Lower Triassic In Jiannan And Peripheral Area Of Eastern Sichuan, Sichuan Basin

Based on the foundation of carbonate sedimentology and the theory of reservoir diagenesis, combining with the instruction of carbonate reservoir geology, the Multi-disciplinary and multi-application technology, and the advanced analyzing method, this paper makes an extensive and thorough research on the sedimentation, diagenesis features, reservoir control factors and patterns of distribution in Member 3 of Feixianguan Formation in Jian Nan area, and from which we get some understanding:1 Analyzing the characteristic of hydrodynamic condition, lithology, sedimentary structures and microfacies patterns, the depositional facies at Member 3 of Feixianguan Formation can be divided into three parts that from west to east it is: open platform facies, platform edge facies and platform edge slope facies. The main environment is platform edge oolitic shoal. Along Gao Fengchang– Shi Baozhai—HJ1 it is open platform facies, and in the east of L10—Li Chuanhe—Shi Zhujiantianba it is the platform edge slope facies. Between the two areas it is the platform edge facies.2 Based on different parts of the oolitic shoal occurring on lithological section in this area, Sedimentation of Member 3 of Feixianguan Formation can be divided into two periods; The early period of the platform shoal is to the west of XC2-CZ1-J30-Shi Zhujiantianba, and to the east F4-B2-YD2-HJ1-FengDumaliang. The depositional thickness is 60-90m; The late period of the platform shoal is to the east of Chang linggang-J30-ShiZhu lixin, and to the west Xiang Zhuwan-L10-LiChuan hetaoyuan- LiChuan Youchaohe. The depositional thickness is 30-60m that is thinner than the early period.3 In the research area Member 3 of Feixianguan Formation can be divided into four fourth order sequence; every fourth order sequence is consist of upward and downward semicycle. The early period the platform shoal develops in downward semicycle of SQ 1~3. The late stage it develops in upward semicycle of SQ 4. Although both of them are oolitic shoal, the origins are totally different, which cause different diagenesis modification and physical property.4 In the research area these are syngenetic disgenesis stage, early diagenesis stage and late diagenesis stage. Based on the effective reservoir distribution and the diagenesis which has essential effect on the pore evolution, the diagenesis facies are classified as 4 types as following:mixed water dolomitization facies, meteoric fresh water dissolution facies, buried corrosion facies and structural fracture facies. The good reservoir developes in overlay areas of multifacies.5 the physical property and pore structure research indicate that the porosity and permeability are mostly low. The porosity is 0~1.5%, and the permeability is 0.01~0.25md. It is a low porosity and low permeability reservoir. The pore structure is poor on the whole, characterized by unevenly distributed micro-throat, and fractures are locally distributed.6 Based on reservoir thickness, porosity, seismic anomaly, the paper made an integrated evaluation to reservoir in Member 3 of Feixianguan Formation, which can be divided into four categories.