Ordos Basin Xifeng Oilfield Reservoir Characteristics, To Extend The Group Of Chang 8 Reservoir

Favorable target areas for exploration are put forward in the paper through researches and evaluation of sedimentary facies, petrologic features, diagenesis, characteristics of microscopic structure of pores, and factors influencing reservoirs of the Chang-8 reservoirs of Triassic Yanchang Formation of the Xifeng oilfield in the Ordos basin.The braided river delta and lake facies were developed mainly in the Chang-8 Age of Xifeng oilfield of the study area. The sub-facies of delta front are dominated with development of (underwater) distributary channel, mouth bar, faraway sand bar, and front edge sheet-shaped sands. Lithology of the Chang-8 oil reservoirs is mainly fine-medium lithic feldspathic sandstone and feldspathic detritus sandstone. Diagenetically authigenic minerals are dominantly kaolinite, chlorite, siliceous, and ferruginous calcite. Diagenetically authigenic mineral combination has obviously regional characteristics. Diagenetic reservoir facies is divided into five sorts.Vertically, various reservoir facies are overlapped each other. Of which the reservoir property of the chlorite-cemented diagenetic reservoir facies is the best, being distributed mainly in the middle parts of the sand body. The Chang-8 reservoirs overall belong to low to extra-low permeability, with two types of pores of dissolution pores-intergranular pores and dissolution pore-dissolution pores. The reservoirs are divided into four categories and six sorts according to the Lithology, porosity and permeability. Horizontally the reservoir physical properties are mainly influenced and controlled by the sedimentary environment, while vertically impacted by the diagenesis.According to the sedimentary facies zones, sand-body distribution law, pore structures, diagenetically regional features etc. three favorable exploration zones are predicted comprehensively by through evaluation, that is, Xuanma-Yuele, Hedao South, and Guchengchuan East favorable-zones...