Analysis of Mesozoic Hydrocarbon Source Rocks in the Tuonamuzangbu area,Qiangtang Basin,Tibet

The Tuonamuzangbu area is situated between the Qiangbei depression and central uplift zone,Qiangtang basin,Tibet,where the hydrocarbon source rocks are mainly limestone and mudstone of sections 1-4 of the Suowa Group 1,upper Jurassic.The hydrocarbon source rocks in this region are thick with relatively low content of total organic carbon(TOC).Their chloroform asphalt A and total hydrocarbon content are also relatively low,organic matter type is medium,and thermal evolution degree is of intermediate-high maturity.The hydrocarbon source rocks have a double-peak distribution of carbon numbers C25 and C27,and are dominated by heavy carbon superiority with low r-wax alkane content.Comprehensive evaluation considers that for the Suowa Group,carbonate of section 3 of and mudstone of section 4 are the better hydrocarbon source rocks,carbonate of sections 3 and 2 is intermediate hydrocarbon source rocks,mudstone and the carbonate of section 1 are poor hydrocarbon source rocks.