控制东营凹陷烃源岩排烃的几个关键因素

Key factors of controlling the hydrocarbon expulsion of the source rock in Dongying Sag

通过东营凹陷钻井取心的观察及不同结构烃源岩地质地球化学特征的比较,从内因、外因两个方面对烃源岩排烃的控制因素进行了分析,并且就烃源岩岩性结构对排烃及成藏的控制作用进行了初步研究.认为内因为有机质类型、丰度及成熟度,反映烃源岩中生烃母质的特征,东营凹陷大量样品测试结果显示烃源岩的生烃潜量、排烃量与有机质丰度呈良好的线性关系;外部因素包括源岩的结构、源岩内有效的运移通道、压力的分布及外部的构造运动等各种地质作用及内、外部环境.研究结果表明,东营凹陷主力烃源岩沙四上及沙三下段具有多种岩性结构形式,其中沙四上及沙三下下部主要发育纹层状泥页岩,油气以远距离侧向运移为主;沙三下上部及沙三中主要发育块状泥岩,油气以垂向运移为主.不同的排烃方式造成了油气分布的差异,沙四型原油分布于凹陷外围,沙三型原油分布于凹陷内围,混合型原油分布于中间地带.

The factors of controlling the hydrocarbon expulsion of the source rock in Dongying Sag are analyzed from internal cause and external cause through the observation of drilling cores and the comparison of the geologic and geochemical characteristics of the source rocks with different structure.The controlling effect of the lithologic structure of the source rocks on the hydrocarbon expulsion of them and the hydrocarbon accumulation is studied.It is held that the internal controlling factors are the type,abundance and maturation of organic matters,which reflect the characters of the hydrocarbon generation material in the source rocks.The testing results of a lot of samples in the sag show that there are linear relationships between the potential hydrocarbon generation amount and the hydrocarbon expulsion of the source rock and the abundance of the organic matters.The external controlling factors include the effective migration pathways and the pressure distribution in the source rocks,some geologic effects such as structure motion and external environment.The research results in this paper show that,there are many lithologic structures in the upper fourth member and the lower third member of Shajiehe Formation,which are chief source rocks in the sag.Lamellar shale is mainly developed in the upper fourth member and the lower part of the lower third member,and the hydrocarbon migration here is mainly lateral in a long distance.Massive shale is mainly developed in the upper part of the lower third member and the middle third member,and the hydrocarbon migration here is mainly vertical.The different hydrocarbon expulsion forms cause the difference in hydrocarbon distribution:the hydrocarbon of the fourth member distributes in the periphery of the sag,the hydrocarbon of the third member distributes in the central part of the sag,and the mixed hydrocarbon of them distributes in the intermediate zone of the two regions.