The Study On Reservoir Characterization And Accumulation Rules Of Chang8Oil Layers In The Northern Of Baima Area, Xifeng Oilfield

The northern of Baima area, Xifeng Oilfield, is located in the northern Shaanbei slope, the southwest of the Ordos Basin. The Chang-8is the main oil producing zone. According to the actual situation and geological characteristics of the local exploration and development, the Chang-8oil-bearing zone is subdivided into the Chang-81, the Chang-812, the Chang-813, the Chang-821, and the Chang-822.Delta is the most of the deposition system in Xifeng area, and most developed in Chang-8oil layers. The study area can be further divided into delta front underwater distributary channel microfacies, mouth bar microfacies, distal bar microfacies, sheet sand microfacies, and inter-distributary bay microfacies.Studies have shown that the main rock type of the Xifeng Oilfield of the north Baima area Chang-8sandstone is lithic arkose. Types of reservoir porosity are mainly intergranular pores, feldspar dissolution porosity. The low porosity and permeability reservoir properties show that the non-homogeneous is very serious. Depositional environment, structure and diagenesis are the three main impacts of the reservoir.The result of the analysis on natures of oil, water and so on, shows the oil of Chang-8oil-bearing beds belongs to conventional oil, which shows terrestrial facies with low density, low viscosity, or without asphaltenes and low moisture content characteristic. And the kind of formation water in the study area belongs to calcium chloride (CaC21). Reservoir type is a strucural-lithologic composite reservoir; drive type is flexible solution gas drive, belong to the unsaturated reservoir.The hydrocarbon enrichment patterns of the Chang-8oil layers:high-quality regional cap rocks for hydrocarbon enrichment provides a good shelter and closed conditions. Good traps in contral of hydrocarbon accumulation. Structural control oil and gas accumulation, in the study of area the formation of structural highs of the nose under the influence of the compaction, these structural highs is a favorable area of hydrocarbon accumulation. Quality of physical properties affects the distribution of oil and gas, penetration of large areas of oil and gas enrichment. Sedimentary facies have some control on oil and gas enrichment; the study has shown that the underwater distributary channel microfacie is the main place of oil and gas accumulation in the study area.