The Main Controlling Factors Of Oil And Gas Distribution On Chang 8 In South Of Shanbei Slope

Ordos Basin is rich in abundant oil and gas resources and it’s the second of Chinese largest oil and gas basins. The study area is located south of Shanbei slope in the Ordos Basin. Chang 8 reservoir group is the researched layer in this text. In order to study the main controlling factors of reservoir’s distribution in this area. Under the guidance of theories of sedimentology and petroleum geology on the basis of abundant data from geology, drilling, logging, well testing, etc. Combined with regional geological setting, the strati graphic distribution and correlation, structural features sedimentary microfacies and sandstone distribution, reservoir characteristics, etc of Chang 8 are comprehensive studied in study area. Finally, the main controlling factors of oil and gas distribution are summarized.Research shows that Chang 8 reservoir group can be divided into 81 and 82. The tectonic setting of Chang 8 is the west-dipping monoclinic and developing with north west to south east nose uplift which is ranked distribution. Chang 8 is delta-front tacies deposition. Overlapping sands of subaqueous distributary channel are the main reservoir. The lithology is mainly light gray — gray fine grained feldspar sandstone. Chang 8 reservoir is low porosity, low permeability ones. The reservoir properties are poor and belong to tight sandstone reservoir. Combining reservoir properties, macroscopic characteristics of the reservoir space, microscopic pore structure characteristics, capillary pressure curve characteristics and thickness and lithology of reservoir in the study area Chang 8 reservoir is divided into class III and IV reservoirs. The analysis of accumulation Conditions in study area were showed that the highest abundance of source rocks is Chang 7 and Chang 9, which is the most important source rocks in the study area. In Chang 8, the widely development of underwater distributary channel sand bodies in delta front is also one of the most favorable accumulation conditions.After comprehensive analysis, the distribution of source rocks, the nose uplift in superface structure of sand body, the thickness and distribution of underwater distributary channel sand bodies are the main controlling factors of reservoirs accumulation. Regional cap of Chang 7,rnudstone and silty mudstone at the top of each sedimentary cycle inside Chang 8 reservoir group are the good capping conditions.