RESERVOIR CHARACTERISTICS OF CHANG 8 OF YANCHANG FORMATION(TRIASSIC) IN LONGDONG AREA,ORDOS BASIN

The Chang 8 Member which is composed of Chang 8~1 and Chang 8~2 sandstone in Lengdong area in Ordos basin is an important oil reservoir.In this paper,the characteristics of reservoir strata is summarized and evaluated on the basis of petrological and physical features.the texture of porosity and the controlling features of reservoir strata.It was shown that the lithotypes are the medium-fine granular arkose and lithic arkose which have the characteristics of low compositional maturity.middle-high texture maturity,low porosity and permeability.The reservoir develops interparticle pore,solution pore and intercrystal pore.The main throat types is the medium-fine throat and fine throat.The sedimentation and diagenesis have played important roles in evolution of resevoir.Sedimentation controlled distribution of reservoir.Such diagenesis as compaction,solution and mentation controlled the physical and texture of porosity.Based on the lithology and physical property the formation can be divided into 4 types.The favourable reservoir is the submerged distributary chanel sandbodies