定量评价盆地的烃源岩生烃潜力是油气勘探中首先要解决的问题。银根—额济纳旗盆地天草凹陷发育多套烃源岩，但究竟哪一套地层是主要烃源岩尚不清楚，也未见对其烃源岩生烃潜力评价的报道。以天草凹陷天2井暗色泥岩为研究对象，采用多项有机质丰度、类型和成熟度指标定量或定性刻画了暗色泥岩的生烃潜力特征，结果揭示：下白垩统巴音戈壁组下段烃源岩有机质丰度最高，热演化处于成熟阶段，有机质类型为Ⅱ2—Ⅲ型，应为天草凹陷的主力烃源岩；下白垩统苏红图组有机质丰度较高，有机质类型为Ⅱ2型，但其烃源岩成熟度不高，为天草凹陷的次要烃源岩；石炭系和侏罗系烃源岩虽有机碳含量高，但生烃潜量值低，有机质类型为Ⅲ型，现今R O>3.0%，处于过成熟阶段，属枯竭的烃源岩。
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The quantitative evaluation of hydrocarbon generating potential of source rocks in the basin is the key problem which should be solved in the oil and gas exploration. Tiancao sag develops many sets of source rocks, but the main source rock is still unclear, and the report about the evaluation of source rock has not been seen. This research takes the dark color mudstone of the Tian 2 well as the dissection object, and takes advantage of many parameters such as organic matter abundance, the type and maturity of organic matter to describe quantitively or qualitatively the hydrocarbon generating potential characteristics of the dark color mudstone. Results indicate that the source rock's organic matter abundance of the lower segment in Lower Crataceous Bayingebi Formation is the highest and the thermal evolution is at the mature stage, the organic matter type isⅡ2—Ⅲ, so it should be the main hydrocarbon source rock of Tiancao sag; The organic matter abundance of Lower Crataceous Suhongtu Formation is higher, whose organic matter type isⅡ2, while its hydrocarbon source rock maturity is not high, therefore, it is the secondary hydrocarbon source rock of Tiancao sag. Although the total organic carbon content of Carboniferous and Jurassic is high, the hydrocarbon generating potential is low and the organic matter type is only Ⅲ, nowadays R O>3.0%, so it is at the overmature stage and belongs to the depletive source rock.
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