西藏羌塘盆地托纳木藏布中生界烃源岩分析

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

位于羌北拗陷与中央隆起带之间的托纳木藏布中生界烃源岩发育,其中最重要的为索瓦组-段-四段的灰岩和泥岩。该区烃源岩厚度大,TOC总体来说相对较低、氯仿沥青"A"和总烃含量较低、有机质类型中等、成熟度较高。烃源岩主峰碳为双峰,高分子量长链烃优势明显,γ-蜡烷含量较低。通过系统分认为索瓦组四段碳酸盐岩和三段泥岩质量较优,三段和二段碳酸岩盐中等,二段和一段泥岩与碳酸盐岩较差。

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 Cz7, 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.