济阳坳陷超压结构差异性及其控制因素

Overpressure structure dissimilarity and its controlling factors in the Jiyang Depression

济阳坳陷作为我国东部渤海湾盆地内重要的富烃坳陷之一,内部具有复杂多样的压力环境。通过对济阳坳陷内各凹陷的实测地层压力统计、泥岩超压测井响应以及超压剖面发育特征的研究,将东营凹陷、车镇凹陷、沾化凹陷和惠民凹陷的超压系统划分为3种:单-强超压系统、复合超压系统与单-弱超压系统。单-强超压系统分布在东营凹陷与车镇凹陷,纵向上发育沙河街组三段-四段一个超压系统,超压幅度大,压力系数可达1.8以上。复合超压系统分布在沾化凹陷,纵向上发育沙一段、沙三段和沙四段3个超压带,且相互独立。单-弱超压系统分布在惠民凹陷,发育沙三段一个超压系统,超压的幅度相对较弱,压力系数不超过1.4。超压结构的差异性与烃源岩发育层系、热演化程度、压力封闭层分布以及断裂活动密切相关。烃源岩分布与演化控制了超压的形成和分布,压力封闭层控制着超压顶底界面,深大断裂控制了超压系统内外横向边界。

Jiyang depression,one of the important petroliferous depressions in Bohai Bay Basin of eastern China,has the most complex and diverse pressure systems. Based on statistics of the measured pressures,log responses of mudstone overpressures and characteristics of over-pressure profiles of many sags in Jiyang depression,we divide the overpressure systems in Dongying,Chezhen,Zhanhua and Huinin sags into three types,namely the single high overpressure system,the compound overpressure system and the single low overpressure system. The single overpressure system distributes laterally in Dongying and Chezhan sags and occurs vertically as one overpressure zone in overpressure Es^3-Es^4,with a relatively large overpressure amplitude and a pressure coefficient over 1. 8. The compound overpressure system distributes laterally in Chezhen sag and occurs vertically as three separate overpressure zones in Es^1,Es^3 and Es^4 respectively. The single low overpressure system distributes laterally in Huimin sag and occurs vertically as only one overpressure zone in Es^3 with a comparatively small overpressure amplitude and a pressure coefficient less than 1. 4. The dissimilarities of the overpressure structures in different sags are closely related to the sequences and the thermal maturities of source rocks,the distribution of pressure sealing layers,and the fault activities,in the sags. The distribution and thermal evolution of source rocks control the formation and distribution of the overpressure system. The pressure sealing layers control the top and bottom boundaries of an overpressure system. The deep-rooted faults control both the inside and outside horizontal boundaries.