东营凹陷沙河街组湖相烃源岩的组合特征

Combination Characteristics of Lake Facies Source Rock in the Shahejie Formation, Dongying Depression

古近系沙河街组是东营凹陷最重要的成藏组合。在前人研究基础上 ,系统采集该组 6 0 0余块烃源岩样品和 30个油田 186个原油样品 ,分别进行了多项有机地球化学测试。结合其沉积序列和地球化学分析结果 ,将沙河街组烃源岩划分为咸水湖相 (沙四段上部 )、半咸水深湖相 (沙三段下部 )和淡水湖相 -三角洲 (沙三段中部 )三种成因类型 ,它们分别对应欠充填、平衡充填和过充填的湖泊类型 ,代表了陆相断陷盆地烃源岩三种最基本的成因模式 ;并发现沙河街组烃源岩存在强烈的非均质性 ,尤其在平衡充填过程中表现更为突出 ,这种非均质性与湖平面的升降变化密切相关 ,据此提出了波动湖相沉积。通过深入的油 -源对比工作 ,确立了咸水湖相和半咸水深湖相烃源岩为东营凹陷的主力源岩。还探讨了有机质的赋存状态和油气运移方式 ,指出咸水湖相烃源岩形成的油气以侧向运移为主 ,形成的油气藏分布在盆地的边缘 ;半咸水深湖相烃源岩形成的油气以垂向运移为主 ,形成的油气藏主要分布在盆地的中心 。

The Paleogene Shahejie Formation (Es) is the most important hydrocarbon accumulation combination in the Dongying depression. On the basis of former researches, the authors collected more than 600 source rock samples and 186 oil samples from 30 oil fields, and carried our organic geochemical testing. According to the combining sedimentary sequences and geochemical analyses, the source rock of the Shahejie Formation can be divided into three genetic models, including saline lake facies (upper Es 4), semi-saline deep lake facies (lower Es 3) and fresh lake facies (middle Es 3), corresponding to under-filled, balance-filled and over-filled lacustrine types respectively. Furthermore, there is intense heterogeneity in the source rock of the Shahejie Formation, particularly in the balance-filling process. This heterogeneity is closely related to the change of lake level. According to this relationship, the authors proposed fluctuating lake-facies sedimentation. Oil-source correlation shows that source rocks from saline and semi-saline lake facies are the main source rock in the Dongying depression. Finally, the authors discussed the occurrence of organic matter and the manner of petroleum migration, and pointed out that oil generating from saline lake facies source rock migrated laterally and accumulated on the margin of the basin, but oil from semi-saline lake facies source rock migrated vertically and accumulated around the center of the basin.