The Formation Mechanism And Distribution Rule Of Yitong Basement Reservoirs

In Yitong basin Chang37well reveals102meter gas bearing layers in the granitebasement at Qijia bury hill, and the gas bearing layer lay in several layers300-500m bellowtop of basement. The gas discovery unveils the basement exploration in Yitong basin, and onthis background the study is made. The researches of the study include basement lithology,igneous rocks periods, reserve layer characteristics, and analyzes basement hydrocarbonaccumulation mechanismThe study make substantial basement lithology, age and reserve layer sample andanalysis works.90wells lithology and relating data was arranged. Field works were alsotaken in the basin margin, supplementing core samples, In total36wells and12fieldbasement sample was taken, and tested34basement zircon ageing.Through studies on basement lithology, reserve layers, and hydrocarbon accumulation,makes following results and conclusions:(1)92%of Yitong basin is composed of granite,6%-7%is morphrous rock(marble,),sedimentary rock ia about1%, and with few tuff(2) In Chaluhe and Luxiang granites are formed in Yanshan period, while in Moliqinbasement are intruded in Haixi, Yinzhi and Yanshan periods, Marble in moliqin are formed inCarboniferous.(3)Granite basements at Moliqin Jianshan bury hill and Chaluhe Qijia bury hill areintruded in sille shapes, while in southeast margin and Wuxing basements are intruded inbatholith shapes.(4)In Yitong basin bellow basement sille it is Carboniferous and Permian carbonate.Compression causes diapirism, making nearby sille uplift and developing substantial fissures,while top sille develop few fissure and maintains its density. This forms favorable reservecaps.(5)Bury hills in Yitong basin have3types: cover bury hill, dirpiring uplift hill and faultblock. Dirpiring uplift hill forms hydrocarbon play composition: bellow reserve layer, abovedense granite cap, lateral source rock, which is the most favorable type of exploration hills inthe future.