渤海湾盆地庙西中南洼围区原油成因类型及分布主控因素

通过原油生物标志化合物参数聚类分析，在对比沙河街组不同层系烃源岩地化特征的基础上，分析了渤海海域庙西中南洼已发现原油的成因类型、来源及其分布规律。结果表明，研究区目前已发现的原油主要有Ⅰ型、Ⅱ型和Ⅲ型3种成因类型，其中：Ⅰ型原油来源于沙三段烃源岩，主要分布在垦利6-4区和蓬莱25区，其进一步可分为Ⅰ₁和Ⅰ₂两个亚类，分别对应中高熟沙三型原油和中低熟沙三型原油；Ⅱ型原油来源于沙三段和沙四段烃源岩，主要分布在蓬莱31区；Ⅲ型原油主要来源于沙四段烃源岩，可能有少量的沙三段烃源岩贡献，主要分布在渤中36区。原油地化特征及分布规律指示研究区为近源成藏特征。综合烃源岩分布特征及断层活动性分析认为蓬莱25区和垦利6-4区原油类型主要受烃源岩控制，而蓬莱31区和渤中36区原油类型和分布受断裂和烃源岩联合控制。

Genetic Types and Main Controlling Factors of Crude Oil Distribution in South-Central Miaoxi Depression of Bohai Bay Basin

Based on the cluster analysis of crude oil biomarker parameters and the comparison of geochemical characteristics of source rocks of different strata in the Shahejie Formation, the genetic types, sources, and distribution of the crude oil discovered in the South-Central Miaoxi depression of Bohai Sea were analyzed. The results show that there are three main genetic types of crude oil. Type Ⅰ comes from the Third Member of Shahejie Formation(Es₃), and mainly distributed in Kenli 6-4 and Penglai 25 areas. It can be further divided into two sub-categories, Ⅰ₁ and Ⅰ₂, which correspond to high-maturity Es₃ crude oil and low-maturity Es₃ crude oil. Type Ⅱ mainly comes from the source rocks of Es₃ and Es₄, and mainly distributed in Penglai 31 area. Type Ⅲ mainly comes from the source rocks of Es₄ with a small amount of source rocks of Es₃, and mainly distributed in Bozhong 36 area. The geochemical characteristics and distribution regularity of crude oil indicate that the study area is characterized by near-source reservoir formation. Based on the analysis of distribution characteristics of source rocks and fault activity, it is considered that the types and distribution of crude oil in Penglai 25 and Kenli 6-4 areas are mainly controlled by source rocks, while the types and distribution of crude oil in Penglai 31 and Bozhong 36 areas are controlled by both faults and source rocks.