Petroleum Geological Characteristics And Prospective Analysis Of Aoligai Faulted Depression In East Gebi Basin In Mongolia

East Gebi basin of Mongolia is close to Erlian basin,Hai-Ta basin and Yin,e basin of China,they have the similar geological background and reservoir condition.? district located in middle and south of Mongolia,administration subjected South Gebi province,Aoligai fault depression is at northeast of ? district,spread direction is NNE,total area is 2000km2.Previously,the Zuunbayan and TsagaanELS oilfield were discovered in East Gebi basin,several years ago,Tamuchage in northeast of basin and Dongsheng contract area were prospected for petroleum and discovered a large scale of oi1&gas reserves,it shows that there are abundant oil&gas resource in East Gebi basin.But only three wells were drilled in Aoligai fault depression,and a little research work was done for this area by previous person,so the object of this paper is doing detailed analysis and study for petroleum geological characteristics,finding out the favorable area,the study result can guide the explore and development direction in the future.By means of the study for the characteristic of the source bed,reservoir and cap cover,the dark mudstone is recognized as a major kind of the source rocks in study area.Two set of source rocks is lower Zongbayin formation and Chagan formation,from the study of organic content,upper and lower section of lower Zongbayin formation is good source rock;middle section of lower Zongbayin formation is medium source rocks,Chagan formation 1s medium-good source rocks.Through the organic geochemical study of the source rocks,the organic type is good;the lower section of lower Zongbayin is best,?1 type.Upper section of lower Zongbayin and Chagan formation is medium,?2-?1 type,middle section of lower Zongbayin is worst,?2-?type.From the study for orgnic evolvement of source rock,the mature window is around 1400m,the mature source formation is below the bottom of middle section of lower Zongbayin formation.In a word,there are two set of maturate source rocks in Aoligai fault depression,Zongbayin formation and Chagan formation,source rock of both formation is thick,and organic matter type is good,have the good hydrocarbon bearing potential.The resource prospect is considerable,estimated total volume of oil&gas resource of Aoligai fault depression is 1.68 hundred million.The major reservoir in study area is middle and lower section of lower Zongbayin formation and Chagan formation,the type is clastic rock,deposited space type is cavity,based on its physical properties study,it belongs to medium porosity and low permeability.The cap cover is majorly lower Chagan formation.Two main types of the source-reservoir-cap assemblage are recognized,self-accumulating and top source-bottom reservoir.Combined the drilling experience in this area,especially oi1&gas showing,reservoir and cap cover assembly,the paper sum up the reservoir bearing condition and collecting rules.