祁连山冻土区木里煤田侏罗系烃源岩地球化学特征

摘要：为了查明祁连山冻土区木里煤田天然气水合物的气源，从QH 1、QH 2、QH 3井采集侏罗系样品44块，在常规的岩石热解和有机碳分析的基础上，进行GC MS分析和显微组分镜下鉴定。样品TOC在14%~166%之间，Ro为071%~079%；泥岩TI大于40，煤小于0。正构烷烃呈前峰型分布，主峰碳为C17-C19，Pr/Ph普遍大于11；三环萜烷以C19TT-C20TT为主峰，C24Te对C26TT有绝对优势；甾烷系列C27-C28-C29甾烷呈反“L”形分布；藿烷系列C31升藿烷占优势，C34、C35升藿烷含量低且G/C30H低，大部分小于02。结果表明，该区侏罗系烃源岩基本处于成熟阶段，有机质为Ⅱ2型-Ⅲ型，主要来自陆相高等植物输入，为河湖沼泽相沉积。有机质丰度较高，属中等-好烃源岩。综合分析认为，研究区侏罗系烃源岩处于成熟度阶段但未到主生气期，不是研究区水合物主力气源岩。

Geochemical Characteristics of Jurassic Source Rocks in the Muli Coal Field,Qilian Mountain Permafrost

Abstract:In order to find out the gas source of gas hydrates in Muli coal field of Qilian Mountain permafrost, forty four Jurassic samples were collected from drilling holes of QH 1,QH 2 and QH 3 for geochemical analysis. On the basis of GC MS experiment and microscopical maceral identification of organic matters, the results show that the ranges of TOC and Ro of samples are 14%-166% and 071%~079%, respectively; mudstones TI is greater than 40, and coals TI is less than 0;the peak of normal alkanes appears in the first and the main peak of carbon distribution is C17-C19,while Pr/ Ph is generally greater than 11; tricyclic terpenes has the main peak with C19TT-C20TT, and C24Te has absolute advantage to C26TT; the distribution of C27-C28-C29 sterane series shows as a reverse “L”; C31 homohopane is an important component in hopane series and the content of C34-C35 homohopane is low, and G/C30H is low and mostly less than 02. The results reveal that the Jurassic source rocks stay in a mature stage;organic matters mainly belong to Ⅱ2-Ⅲ type, which are mainly from higher plants;the sedimentary environment belongs to swamp facies; the organic matter abundance is relatively high, indicating to be medium good source rocks.It can be drawn a conclusion that Jurassic source rocks in the study area are keeping in an oil generating stage and not the main gas source rocks.