塔里木盆地喀什凹陷烃源岩地球化学特征和油源对比

塔里木盆地喀什凹陷油气成藏条件优越,有很好的勘探前景,但除阿克莫木气田外,并无其他突破,一个重要原因是对主力烃源岩层认识不清。通过对喀什凹陷9个野外剖面系统采样和地球化学分析,认为下石炭统和中-下侏罗统为喀什凹陷的主要烃源岩层系,其中下石炭统Ⅱ型海相泥岩和泥灰岩为中等-好烃源岩,分布广泛,厚度大,现今处于高成熟阶段,以生干气为主;中侏罗统杨叶组Ⅱ型湖相泥岩和下侏罗统康苏组Ⅲ型沼泽相泥岩较次,中-下侏罗统烃源岩处于成熟阶段,以生油和轻质油为主。油源对比分析结果表明,黑孜苇油苗、克拉托油砂和阿克1井油源均来自于石炭系,研究认为石炭系为喀什凹陷的主力烃源岩层;中-下侏罗统烃源岩生烃潜力有限且分布范围局限,对油气成藏贡献较小。 

Geochemical characteristics of source rocks and oil-source correlation in the Kashi Sag,Tarim Basin

The Kashi Sag in Tarim Basin shows good hydrocarbon exploration prospects with superior accumulation conditions. However, the only discovery is the Akmomu gas field. One important reason is that there is no clear understanding of hydrocarbon source rocks. Through systematic sampling and geochemical analysis of 9 profiles in the Kashi Sag, we concluded that the Lower Carboniferous and Lower-Middle Jurassic are the main hydrocarbon source rocks in the Kashi Sag. The Lower Carboniferous marine mudstones and marlstones are medium-good hydrocarbon source rocks with type Ⅱ organic matter that are widely distributed with large thickness. They are highly mature and mainly produce dry gas. Lacustrine mudstones of organic matter type Ⅱ in the Middle Jurassic Yangye Formation and swamp facies mudstones of organic matter type Ⅲ in the Lower Jurassic Kangsu Formation are lower quality potential sources. They are mature and mainly produce oil and light oil. Oil-source correlation indicated that the source rocks of Heiziwei oil seepage, Kelatuo oil sand and well Ake1 natural gas is Carboniferous, which is the main source rock sequence in the sag. The Lower-Middle Jurassic source rocks have restricted hydrocarbon generation potential and are distributed locally and were less important for hydrocarbon accumulation.