Burial History Of The Kongquehe Region In Tarim Basin

Appropriate method was changed to calculate the main stratadenudation of the late period of Ordovician, Silurian, Carboniferous,Jurassic through analyze structual evolution of Kongquehe block andsummarize calculation of strata denudation and principle and methodof burial history. On such a basis, the 23 well's burial history ofKongquehe block were rebuilt and burial curves were analyzed,moreover,the paper analyzed the different type of burial history ofKongquehe block and the relation between the burial history andhydrocarbon-generating period of soure rocks in combination withpalaeogeotemperature in the region.In a conclusion, the burial history can be divided into three sortsas follows:First sort: The model of marginal uplift bury andhydrocarbon-generating evolutionThere are two series of source rocks, i. e Cambrian-lowerOrdovician and Jurassic. According to analysis of structual evolutionof Kongquehe area, The eastern Tarim and Qunke region in the marginof sag area are palaeotopography of Caledonian, Kuerle nose-uplift ispalaeouplift. The region was uplifted strongly, and the stratum waserosed to the large extent, the erosional thickness is about2500m.Ordovician is the main matured period of source rocks in upliftarea, the matured geotemperature of the source rocks of Cambrian andlower Ordovician changes from 60 ℃in upper and middleOrdovician to 130℃in the late period of Ordovician, the temperaturehas evoluted to a large extent in a shorter period. In lateOrdovician ,the strong uplift ended source rocks'evolution in marginaluplift area, the state went on untill Cretaceous,and remain uplift at alltimes, the uplift area subsided again in Cenozoic. At present, themaximum buried depth in the eastern Tarim lower swell is equal to thelate Ordovician's, the burial depth of Cambrian's source rocks is5000-6000m, but at the time, the temperature gradient in Tarim basinis lower, only lies in between 90℃and 120℃, and has no ability togenerate hydrocarbon secondly; The burial temperature of theCambrian's source rocks on Shaya uplift lies in between 120℃and150℃. As the palaeogeotemperature in late Tertiary exceeded themaximum palaeogeotemperature in late Ordovician, the source rocksin Cambrian-lower Ordovician may generate hydrocarbon secondly inlate Tertiary. At present, the source rocks in Jurassic reaches the hydrocarbon-generating temperature just now. Second sort: The model of successive subsiding hydrocarbon-generating evolution on the margin of depress. The model is mainly discovered on the west and north margin ofCaohu sag. There are three series of source rocks of Cambrian-lowerOrdovician, Carboniferous and Jurassic. Its sedimentary velocity anderosion in middle and upper Ordovician is lower than the deeper partsof sag,the depth of the source rocks of Cambrian-lower Ordovician isin between 3000m to 5000m, thermal temperature is 120℃~160℃。Sediment is slow during late Palaeozoic and Cenozoic. thesedimentary depth is 8000~10000m, the temperature is 180℃~230℃.hydrocarbon-generating action is successive, and the source rocks liesin high –matured state. The source rocks of Carboniferous reached hydrocarbon-generating temperature and enter threshold of hydrocarbon-generationin middle Cretaceous, however, they are still in low-matured at thepresent time. The source rocks of Jurassic reached hydrocarbon-generatingtemperature in late Tertiary, but are still in low-matured at the presenttime. Third sort: The model of hydrocarbon-generating evolution indeep sag There are two series of source rocks in some regions includingthe south of Caohu sag, Manbei sag, Yingjisu sag, in addition, thesource rocks of Carboniferous has been discovered in Caohu sag.Thesedimentary velocity in middle and late Ordovician-Silurian was thelargest, the depth reached maximum palaeoburial depth in the lateSilurian. The depth is 8000m~12000m from the west to the east. thesource rocks of Cambrian-lower Ordovician reached thehydrocarbon-generating temperature in late period of early Ordovicianand the hydrocarbon-deading temperature exceeding 240℃in Silurian,hydrocarbon-generating action stoped.The sags uplifted and eroded toa large extent in late Silurian, the erosion thickness was1300m~3000m.The burial depth is equal to maximum burial depth ofSilurian's.There are quite a little petroleum uncracked, and have hope...