潜江凹陷蚌湖地区潜江组超压成因机理

蚌湖向斜带位于潜江凹陷中部,其潜江组普遍发育超压系统.综合超压成因机理的各种分析方法,基于测井曲线特征和烃源岩成熟度特征,从压实不均衡和生烃作用两方面对蚌湖地区的超压成因机理进行了系统分析.研究结果表明,1在超压段泥岩声波时差曲线偏离正常压实线,其拐点深度为2150~3180 m,蚌湖地区储层实测超压顶界面深度约为2200 m,在埋深较浅地区,超压成因以不均衡压实作用为主,在埋深较大地区,超压成因为不均衡压实和生烃共同作用;2超压顶界面埋深与生烃门限表现出较好的一致性,在2200 m深度其镜质体反射率Ro值为0.55%,说明生烃作用对蚌湖地区超压的发育亦具有一定的贡献,由此认为,压实不均衡和生烃增压作用是蚌湖地区超压发育的主要机理.

Qianjiang Formation Overpressure Mechanism in Banghu Area of Qianjiang Depression

Banghu syncline is located in the center of Qianjiang depression,and overpressure distributes widely inthe Qianjiang formation. The overpressure mechanism in the Banghu area is studied by two aspects which are thecompaction disequilibrium and hydrocarbon generation. The result indicates that the Qianjiang formation of Banghuarea shows a compaction disequilibrium situation where mudstone acoustic time curve presents a diverge comparedto the normal line,with the inflexion depth between 2150～3180 m. Meanwhile,the measured top depth of overpressureis under 2200 m. This verifies that the compaction disequilibrium causes the overpressure in the area. On the otherhand,there is a good coherence between the top depth of the overpressure and the hydrocarbon generation fastigium,and the Ro is 1.0% at the depth of 3200 m,which verifies the contribution of the hydrocarbon generation to theoverpressure development. Therefore,it can be concluded that hydrocarbon generation and the compaction disequilibriumare the main mechanism of the overpressure development.