吐哈盆地石炭系—下二叠统烃源岩地球化学特征

Organic geochemistry of Carboniferous and Lower Permian source rocks,Turpan-Hami Basin,NW China

选择吐哈盆地有代表性的石炭系、下二叠统野外露头和探井岩心碳酸盐岩和泥质岩样品,从有机质丰度、类型、成烃热演化等方面分析其有机地球化学特征。分析结果表明,泥质岩的有机质丰度总体高于碳酸盐岩,为较好的烃源岩,而碳酸盐岩有机质丰度总体低,基本为非烃源岩。碳酸盐岩和泥岩的母质类型主要为Ⅲ型,很少部分为Ⅱ2型,碳酸盐岩比泥岩的母质类型稍好。井下烃源岩主要处于成熟—高成熟阶段早期,露头样品成熟度有较大的变化范围,从成熟阶段到高—过成熟阶段均有分布。钻井样品成熟度总体偏低主要与钻井样品埋藏总体不是很深有关,露头样品成熟度较高可能与经历的构造作用及局部较高的地温有关。根据热演化剖面特征推测好的石炭系—下二叠统烃源岩应分布于凹陷较深部位,且对天然气的生成较为有利,火山岩为深部位天然气聚集的较好储集层。

Organic geochemistry characteristics of the carbonate rock and mudstone samples from cores in the exploration well and outcrops in the Carboniferous and Lower Permian, Turpan-Hami Basin are analyzed in terms of organic matter abundance, type, hydrocarbon generation and thermal evolution, etc. The mudstone is higher in organic content than carbonate rock, belonging to relatively good source rock; whereas, the carbonate rock has lower organic content and is basically non-source rock. The matrix types of both carbonate rock and mudstone are grouped into Type III （dominant） and II 2 （less）. The carbonate rock is a bit better than the mudstone in organic types. The source rock of downhole is at the early mature to highly mature stage. The maturity of outcrop samples has a great variation range, from mature to overmature. The lower maturity of well samples is related to the smaller depth of the samples. The higher maturity of outcrop samples may be related to the tectonic movement and high geotemperature. Based on characteristics of thermal evolution, more effective source rocks are distributed and can generate more natural gas in the deeper location of the sag. The igneous rocks are better deep reservoirs in which natural gas accumulates.