有效烃源岩的识别方法

IDENTIFICATION METHODS FOR EFFICIENT SOURCE ROCKS

有效烃源岩的识别和评价是含油气系统和油气成藏研究的基础。以往常用有机碳含量下限 (0 .5 % )作为烃源岩是否有效的判识标志。东营凹陷沙河街组厚达 10 0 0～ 15 0 0m的暗色泥岩的有机碳含量大于 0 .5 % ,因此长期以来人们把其作为有效烃源岩。对东营凹陷进行精细的油源对比发现 ,其有效烃源岩绝未达到 10 0 0m之厚 ,对油气藏真正有贡献的主要为沙四上和沙三下亚段有机碳含量在 1.5 %以上的烃源岩 ,它们控制了东营凹陷各亿吨级大油田的形成。因此 ,有效烃源岩下限标准的确立 ,应以研究区的实际情况而定 ,可首先通过油源对比确立有效烃源岩层段 ,然后运用测井方法删除非烃源岩夹层 ,并获取烃源岩的各项评价参数 ,从而完成有效烃源岩的识别和评价工作。

For a long time, the source rocks from 1?000 to 1?500 meters in thickness were thought to be the efficient source rock in Donying depression, because the content of organic carbon in the dark mudstones is over 0.5 percent, which has been the reasonable mark for identifying the efficient source rock. But the precise oil source comparison shows that the thickness of the source rocks is impossible up to 1?000 meters or more. The source rocks containing organic carbon of 1.5 percent in the upper Sha 4 and the lower Sha 3 subsections mainly attributed to hydrocarbon reservoirs and controlled the formation of millions tons of oil gas fields in Dongying depression. Therefore, the minimum organic carbon content of the efficient source rocks should be determined according to the actual condition in that area. Firstly, the efficient source rock layers may be identified with the oil source comparison method. Then the evaluation standard of the efficient source rocks can be obtained with the combination of sedimentary and geochemistry characteristics of the different layers. The rid of intermediate layer in the non source rock and kinds of parameters about source rocks can be achieved by using logging method. Finally, the identification and evaluation of the efficient source rocks may be finished.