The Characteristics Of Petroleum Reservoir Of Chang 8 In Xunyi Exploration Area,Southern Of Ordos Basin

Ordos Basin is the second largest sedimentary in China,which has rich oil and gas resources.During the past hundred years of effort,Ordos Basin has made remarkable achievements in oil-gas exploration and exploitation.However,on the whole,in the middle part and north part of the Ordos Basin, oil-gas exploration and exploitation degree is high,and the south part of the Basin is relatively low.In recent years,with the development of economic,the oil-gas exploration and exploitation in south part of the Basin has been placed on the agenda.Research area lies in Weibei uplift,which is in the south of Ordos Basin.The achievements made by predecessors in this area are relativity low in stratum,structure,the condition and key controlling factors of oil-gas accumulation.Thus,strengthening the study on these aspects has great practical significant to the next step of oil-gas exploration and exploitation work.This article study the the tectonic development and evolution of Weibei uplift,which based on field observation and the theory of Sedimentology,Tectonics and petroleum geology.Combined field observation and indoor comprehensive study,we get conclusion of the stratum feature,structural feature and the sedimentary feature in Xunyi area. On that basis,we analyze the source rock condition and reservoir condition by using testing data.And at last,we analyze the condition and key controlling factors of oil-gas accumulation of Chang8 reservoir.The study concludes that:(1)Weibei uplift formed in indosinan period and developed in Yanshan-Xishan period.There are large quantities of faults and folds in Weibei uplift,which has certain effects of the oil-gas accumulation;(2)The Yanchang Formation in the east of Xunyi exploration area are preserved well,but most areas in the west of Xunyi exploration,formation has been denuded above Chang4+5.Overall,the structural framework of Xunyi exploration is higher in the south rather than north and higher in the east rather than west.And in this area,it main develops two underwater distributary channel sand body,of which the provenance comes in southwest direction.(3)The study of reservoir suggests that Chang 8 reservoir lithology is lithic arkose and has the characteristic of low mineral maturity and high textural maturity.(4)By comprehensive assessment with characteristics of sourcerock in Xunyi exploration,it shows that the source rocks have high abundance of organic matter, and the organic types are mainly type Ⅰand typeⅡ,and organics are almost in the stage of maturity.(5)The reservoir type of Chang 8 reservoir in Xunyi exploration are mainly lithologic reservoir and structural-lithological reservoir.The major controlling factors of petroleum are high quality source rocks,effective reservoir sand body and abnormal high pressure.And in this area,oil-gas accumulation models of Chang 8 reservoir is near-source rocks accumulation.