Oil Reservoir Characteristic Analysis Of Yan6 And Yan9 In Yan'an Formation In The Southeast Area Of Luopangyuan, Dingbian Oilfield

The southeast area of Luopangyuan in Dingbian oilfield is located in the transitional zone of Shanbei slope and Tianhuan depression, Ordos basin, which is the one of the important oil-producing area of Yanchang oilfield. Yan6, Yan9 in Yan'an formation and Chang6, Chang9 in Yanchang formation are all pay layers, and the Yan9 is the main pay layer, it outputs about 100,000 tons per year with a high output of oil per day. With a comprehensive analysis of the massive data, including geology, drilling cores, well logging and assay data, we finely studied the structural configuration of the pay layers, sedimentary micro-facies, reservoir characteristics, reservoir four-property relationship, reservoir type, reservoir controlling factors and its accumulation models of Yan6 and Yan9 in Yan'an formation in the southeast area of Luopangyuan.The superface structures of both Yan6 and Yan9, which develop 3-4 nasal convex structures in NE trending, are western dipping slopes. Yan6 and Yan9 are belong to delta plain braided river deposition, and their reservoir micro-facies include distributary channel, flood fan and bank sand etc. The lithology is mainly detrital quartz fine sandstone, and its pore type is mainly the original residual intergranular pores, the average porosity is 15.4%, the average permeability is 24.23x10-3?m2, the sorting coefficient is 2.19, the average pore throat is 2.99?m. So the reservoir belongs to medium-pore coarse-throat and low permeability reservoir. For Yan6 and Yan9 reservior, the lower limit of resistivity are respectively 9?·m and 6.5?·m, the ithology all above oil spot fine sandstone, physical properties are 12.3% ? 3×10-3?m2, the AC is more than 232 ?s/m and the oil saturation is greater than 35%.The reservoir type of Yan6, Yan91 and Yan92 are mainly lithologic updip pinchout reservoir, driving by the elasticity, solution-gas and edge water. The reservoir type of Yan93 is lenticular sandstone reservoir, driving by the elasticity and edge water. The controlling factors of reservoir distribution are mainly source rock, sedimentary micro-facies, source-reservoir-caprock configuration, structural characteristic and oil and gas transport conductor, and the factors above are mainly controlled by the ancient morphology. The Yan6 and Yan9 formation mainly reservoir accumulation model is slope-highland area-braided channel of delta plain accumulation model.