塔里木盆地富满地区吐木休克组烃源岩有机地球化学特征及其油气勘探意义

Organic geochemical characters of source rock and significance for exploration of the Tumuxiuke Formation in Fuman area,Tarim Basin

塔里木盆地富满地区吐木休克组烃源岩作为近期勘探新发现的烃源岩层,具有良好的油气勘探前景,因此亟需对其进一步开展烃源岩地球化学评价,以便更好地指导勘探。通过总有机碳含量、岩石热解测定以及饱和烃、芳烃色谱-质谱(GC-MS)等分析方法对富满地区吐木休克组黑色泥岩及灰色泥岩岩屑样品进行了定性和定量表征。研究结果表明,吐木休克组烃源岩有机质丰度高,均值为3.4%,氢指数(HI)最高可达到590 mg/g,干酪根类型以Ⅱ型干酪根为主,为一套好-极好的优质烃源岩。从分子地球化学特征来看,烃源岩形成于弱还原偏咸水的海相沉积环境中,以低等水生藻类作为主要成烃生物。基于热解峰温T_(max)及饱和烃生物标志化合物和芳香烃热成熟度参数,吐木休克组烃源岩总体处于低成熟-中等成熟阶段,具有良好的生烃潜力。富满地区东南部区域作为环满坳陷西部斜坡区,可能分布有更厚、更优的吐木休克组烃源岩,且烃源岩可能已达到更高的热演化程度,其对奥陶系油气资源的贡献不可忽视。

[Objective]As a newly discovered source rock in the Fuman area of the Tarim Basin,the source rock of the Tumuxiuke Formation has good petroleum exploration prospects,and the geochemical evaluation of the source rock is conducive to guiding exploration.[Methods]The qualitative and quantitative characterization of drill cuttings from the Tumuxiuke Formation in the Fuman area was carried out by means of total organic carbon(TOC)content,Rock-Eval pyrolysis,and GC-MS analysis of saturated and aromatic hydrocarbons.[Results]The results show that the source rock of the Tumuxiuke Formation is a good to excellentsource rock,with an average TOC content of 3.4%.The highest hydrogen index(HI)is 590 mg/g,and the kerogen type is mainly type II.According to the molecular geochemical characteristics,the source rock was formed in a marine sedimentary environment with weakly reducing brackish water,with aquatic algae as the primary hydrocarbon-generating organisms.Based on the peak temperature(T_(max))of Rock-Eval,saturated hydrocarbon biomarker compounds,and aromatic hydrocarbon thermal maturity parameters,the source rock of the Tumuxiuke Formation is generally in the mature-medium mature evolution stage and has good hydrocarbon generation potential.[Conclusion]As the sedimentary center of the Huanman Depression,the southern Fuman area may have thicker and higher-quality Tumuxiuke source rock with a greater degree of thermal evolution,whose contribution to the oil and gas resources in the Ordovician cannot be ignored.