东营、沾化凹陷压力结构差异及其影响因素

Difference in Pressure Structure of Dongying Sag and Zhanhua Sag and Its Control Factors

根据东营、沾化凹陷的实测地层压力的统计、泥岩声波时差测井响应以及超压剖面发育特征的研究,将东营、沾化2个凹陷的超压划分为单一强超压和复合超压2种超压系统。单一强超压系统分布在东营凹陷,纵向上发育1个超压系统(沙三—沙四段),超压系统发育规模大、分布范围广、超压幅度强,压力系数可达2.0。复合超压系统分布在沾化凹陷,纵向上发育3个超压系统,上超压系统位于沙一段,超压幅度较弱,最大压力系数不超过1.4;中超压系统位于沙三段,超压幅度较强,压力系数可达到1.8;下超压系统位于沙四下亚段,超压幅度也较强。压力结构的差异性与烃源岩的发育层系、热演化的程度、压力封闭层的分布以及断裂活动密切相关。

Dongying sag and Zhanhua sag are two important hydrocarbon-rich sags in Jiyang depression, there is over-pressure phenom- enon in them, but their pressure structures are different. The study of the statistics of formation pressure measurement data, the acoustic logging response of mudstone and the characteristics of over-pressure sections shows there are two types of over-pressure systems in two sags：single strong over-pressure system and compound over-pressure. Vertically,there is one single strong over-pressure system in the Es3-ES4 of Dongying sag,which is of large development scale,wide distribution and large overpressure strength,whose pressure coeffi- cient can reach to 2.0. There are three over-pressure systems in Zhanhua sag. The upper one is in Es1 , its highest pressure coefficient can be as large as 1.4 ; the middle one is in Es3 ,it has a strong over-pressure amplitude, and its highest pressure coefficient can be as large as 1.8 ; the lower one is in Es4, it has also a strong over-pressure amplitude. The difference in pressure structure of different sags is controlled by the strata and thermal evolution degree of source rock ,the distribution of sealed pressure layers and the activity of faults.