东营凹陷湖相盆地类型演化与烃源岩发育

对东营凹陷沙三段中、下亚段和沙四段上亚段3套主力烃源层的地层层序、岩性组合、微观结构特征和有机质丰度进行了分析,研究了湖相盆地类型与烃源岩发育的关系.东营凹陷在沙四段上亚段和沙三段下亚段沉积时期为均衡补偿盆地,受气候的影响显著,因而这两个层段岩性组合易于变化、非均质性强,表现为由纹层理发育的泥页岩与块状泥岩形成的不等厚互层沉积,有机质丰度整体较高,且频率分布曲线上呈现双峰形特征.相应地,在微观尺度上,固体颗粒有机质赋存方式以“富集有机质”为主.沙三段中亚段沉积时期,表现为过补偿盆地,受气候影响较小,烃源岩非均质性不明显,“富集有机质”含量低,有机质丰度低于前两个层段,且其频率分布呈现单峰形特征.分析结果表明,沙四段上亚段和沙三段下亚段是东营凹陷优质烃源岩形成的主要时期.

Evolution of lake-basin types and occurrence of hydrocarbon source rocks in Dongying Depression

The stratigraphic sequences,lithological association,microscopic textures and organic matter of the Shahejie Formation in Dongy-ing Depression were analyzed.The impacts of lake-basin types on the occurrence of hydrocarbon source rocks were investigated.The aggradational sequence expression indicates that the lake-basin sediments in the Upper Es⁴₂-3 and the Lower Es³₂-3 sections are the balanced-filled type.Under the strong influences of climate,these two sections show great heterogeneities and high abundance of organic matter with double peak in the frequency distribution curve.The enriched solid organic matter was the main composition in microscopic scale.The Middle Es³₂-3 section had progradational sequence expression of over-filled basin characteristics.Accordingly,the influence of the climate was not so strong,and this section show less change in rock types,and hydrocarbon source rocks have lower organic abundance with a single peak in the frequency distribution curve.There only existed a little“enriched solid organic matter”.The study results indicate that the Upper Es⁴₂-₃ and the Lower Es³₂-3 sections are the favorable period for generating excellent hydrocarbon source rocks in Dongying Depression.