层序地层地球化学及其在油气勘探中的作用

层序地层地球化学主要研究基于层序地层格架下的烃源层空间分布特征和源岩有机质的地球化学性质随层序、体系域的变化规律。以大民屯凹陷为实例的研究结果表明,层序地层地球化学研究在油气勘探中具有4个方面的主要作用:(1)预测未钻井或未取心地区烃源层空间分布特征和源岩有机质地球化学性质;(2)通过细化烃源岩评价单元,提高资源量计算中烃源岩体积估算和有机质性质评价的精度;(3)为基于层序地层格架的油气成藏系统研究提供“油气源”和“资源量”的要素;(4)可以作为盆地沉积充填分析的线索,并对已建立的层序地层格架进行检验和校正。层序地层地球化学研究不仅对中国东部老油田隐蔽油气藏的勘探工作具有重要的意义,对勘探程度低、钻井少、源岩取心少的西部含油气盆地中的烃源岩评价工作更为有效。

Sequence stratigraphic geochemistry and its application to hydrocarbon exploration

Sequence stratigraphic geochemistry principally studies the distribution and geochemical characteristics of source rocks in different sequences or systems tracts under a sequence stratigraphic framework. A research in Damintun depression, northeast China shows that sequence stratigraphic geochemistry has the following important significance in hydrocarbon exploration: (1) predicting the distribution of source beds and geochemical characteristics of organic matter in areas without drilling wells or source rock cores, (2) increasing the precision of volumes estimation of source rocks and geochemical appraisement of organic matter in resources assessment, (3) determining the “hydrocarbon origination” and “resources quantity” for petroleum system under a sequence stratigraphic framework, and (4) studying the sedimentary filling histories and testing the sequence stratigraphic framework previously constructed. Apart from in lacustrine basins in eastern China, sequence stratigraphic geochemistry is of especially important significance in source rock evaluation in some basins of western China, where only a few wells were drilled, and insufficient source rock cores are available.