渤海湾盆地东营凹陷沙河街组四段膏盐层及地层压力分布特征

Distribution characteristics of evaporates and formation pressure of the fourth member of the Shahejie Formation in the Dongying Sag,the Bohai Bay Basin

刘晖 操应长 姜在兴 王升兰 王艳忠 徐磊

Liu Hui Cao Yingchang Jiang Zaixing Wang Shenglan Wang Yanzhong Xu Lei

渤海湾盆地东营凹陷古近系沙河街组四段垂向上发育3套膏盐岩,膏盐韵律层具有明显的蒸发成因的沉积序列。膏岩层在平面上呈环状分布,从湖盆中心向盆地边缘依次沉积盐岩-石膏-泥膏岩-碳酸盐岩-泥灰岩-碎屑岩。在声波时差计算地层压力系数和实测压力统计的基础上研究发现,古近系地层压力在垂向上表现为浅层正常压力系统和深层超压系统的"双层结构"。平面上,异常压力的分布范围与膏盐岩的分布具有较好的对应关系。膏盐岩地层的压力封闭和物性封闭的双重封闭机制是东营凹陷沙河街组四段地层超压形成的重要控制因素之一。

Three sets of gypsolyte-salt rocks occur vertically in E(the fourth member of the Shahejie Formation) of the Dongying Sag,the Bohai Bay Basin.The gypsolyte-salt rhythmic units show apparent depositional sequence of evaporation in genesis.On plane view,the gypsolyte-salt rocks are in ring-like distribution,and salt rock,gypsolyte,argillaceous gypsolyte,carbonate,marl,and clastic rock occur successively from the center to the border of the basin.Studies based on formation pressure coefficient calculation through interval transit times and statistics of the measured pressures show that the Paleogene presents vertically a "double layer structure" with normal pressure at the upper part and abnormal high pressure at the lower part.On plane view,the distribution of the abnormal pressure matches well with that of the gypsolyt-salt-rocks.It is suggested that the gypsolyte-salt-double seal mechanism of pressure seal and physical property seal is one of the key elements controlling the formation of the abnormal pressure in E in Dongying depression.

10.11743/ogg20090306