| The study area locate in the northwest of Zhidan County, South-central of Yishan slopeErdos basin. The target stratum is Chang2oil reservoirs group. Based on logging, drilling,well-logging, oil testing data, data of experimental analysis and so on, using modern geologicaltheory and various processing software, the author carries out the study of sedimentary stratigraphiccorrelation, the distribution of sedimentary facies and sandstone and comprehensive geologicalresearch of Chang2reservoir. Identifies the regularity of the spacical development and distributionof Chang2sandstone reservoir, carries out the comprehensive classification evaluation, findsout controlled factors of the distribution and enrichment of the Chang2oil reservoirs, forecaststhe favorable oil accumulation zone.Suffered erosional cutting effect, the strata in the study area is fluctuated acutely. The topof Chang2stratum in partial area has lost. The dip direction of the formation is west bysouth.The structure is consistent with the regional monoclinic background.Nose-upliftingstructures are developed. Chang2is Delta front parfacies deposition. The lithology mains withfeldspathic sandstone and small amounts of lithic arkose. Chang2reservoir is characterized bycharacterizedchmesoporosity and low permeability. Diagenesis is strong and the diageneticevolution stage reached into “B” stage of late diagenesis period. Pore types maining withintergranular dissolved pore contain intergranular pore, intergranular dissolved pore,intragranular dissolved pore, moldic pore, intercrystalline pore, micro fracture and soon.Composite types of microstructure consists of mesoporosity~macroporous-fine throat,small pore~mesoporosity-fine throat, small pore-fine throat and small pore-micro throat.Theresults of sensitivity evaluation are weak and weak to medium velocity sensitivity, weak tomedium and medium water sensitivity, weak acid sensitivity, medium salinity sensitivity. Thereservoir has strong anisotropism. Reservoir thickness, porosity and permeability is controlledby sedimentary facies belt, has a certain direction. The common percolation area of oil-watertwo phases is narrow and the bound water saturation is higher. The reservoir is hydrophilic.According to comprehensive classification evaluation standard of Chang2reservoir,there are a total of four types including Ⅰ, Ⅱ, Ⅲ, Ⅳ in Chang2reservoir, corresponding to good reservoir, medium reservoir, mainly poor reservoir, poor reservoir and mainning withII, III.The distribution and enrichment of Chang2reservoir is controlled by structure,sedimentary facies and the pre Jurassic palaeogeomorphology. |
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