The Source Kitchen And Hydrocarbon Generation Of Source Rocks In Wuliyasitai Sag,Erlian Basin

Wuliyasitai Sag is unique in terms of tectonic features,type of source rocks and oil properties compared to other hydrocarbon-rich sags in Erlian Basin,which is mainly characterized of thick strata?more than 4500m?,relatively poor type of source rocks?dominated by organic facies D/E?and light oil.Refined source rocks analysis by 8wells logging geochemical evaluation indicated that the sag is dominated by organic facies D/E,and organic facies C source rock only develop in some wells of K₁bt₁.Source rocks of the sag mainly develop between the K₁bt₁ and K₁ba,they also locate above or below the maximum lake flooding surface and migrate to gentle slope.The vitrinite reflectance of source rocks range from 0.5%to 1.0%,and the threshold depth of hydrocarbon generation is from 1900 to 2000m.The source kitchen can be quantitatively characterized by combining with thermal history parameters of the sag,the hydrocarbon expulsion center is located in the middle sub-sag,and the hydrocarbon expelled intensity can reach 1.2?1.8 mmt/Km².The type of hydrocarbon is mainly oil at present,and oil accumulate in the middle slope zone,the total oil expelled is 130 mmt.There are significantly different hydrocarbon generation features between organic facies D/E and typical organic facies C source rock?dominated by laminated and texture algae?,organic facies D/E source rock is with a high oil window temperature,and the expelled oil is light,whereas organic facies C source rock can expel low mature oil at early stage and light oil can be discharged at mature period.The API data of oil which have been found range from 35°to 45°,classified as light oil,meanwhile the oil is characterized of high wax and low sulfur content compared to other sags in Erlian Basin,the physical properties of discovered oil correspond to the theoretical characteristic of expelled oil from organic facies D/E source rock at this stage.