The Research On Oil And Gas Enrichment Factors Of Chang8₁ Reservoir Of Yanchang Formation In Zhenyuan-Jingchuan Block Of Ordos Basin

After several years of oil and gas exploration at Zhenyuan-Jingchuan block in Ordos Basin, distribution of chang81 subaqueous distributary channel is gradually clear. Oil potential resource is expected to be 16039.2×104t, which showed that the reservoir has bright prospects. Large area, low abundance, low permeability, strong heterogeneity are the main features of chang81 reservoir. These features led to unclear understanding of oil and gas accumulation, which becomes a bottleneck to achieve further exploration.In order to solve the difficulty, on the basis of existing research results, this paper starts from the reservoir sediment characteristics, and methods of combination to macro and micro, regional data and core data are used extensively. Diagenesis, properties and micro-pore configuration of reservoir are studied by means of sides identification, grain-size analysis, mercury penetration analysis and SEM etc. Reservoir Evaluation criteria is established, and then to analysis the impact of the major controlling factors of oil and gas accumulation.The results show that delta front subaqueous distributary channel is the main facies of chang81 reservoir sandstones at Zhenyuan-Jingchuan block. Chang81 sandstone which is now in phase A of diagenesis, is typical of low porosity, low permeability reservoir. Residual intergranular pore, corrosion intergranular pore, and dissolution of feldspar grains within the pore are effective pore types of study area. In the evolution of diagenetic, compaction and carbonate cementation which destroyed the primary pore, reduce the reservoir properties and enhance the heterogeneity of the reservoir. Development of chlorite argillan protect primary intergranular pore effectively. Induced porosity is positive to improve reservoir properties conditions, which produced by dissolution of feldspar and lithic grain.Chang81 reservoir is mainly distributed in chang812 layers. According to analysis of oil-bearing structures, sedimentary facies, diagenetic facies, chang812 reservoir is lithology sandstone oil, which is controlled by the tectonism and thickness of sand weekly. Subaqueous distributary channel is the basic elements that controlling oil, on the basis, diagenesis play a key role on the control of enrichment of oil reservoir.