饶阳凹陷洼槽区地层压力特征及成因机制

根据地层压力实测数据和地层压力模拟计算,对饶阳凹陷洼槽区的地层压力分布特征及其成因机制进行研究。结果表明:饶阳凹陷洼槽区古近系普遍发育超压;纵向上,存在东营组、沙一段和沙三段三套超压层系;可划分为单超压结构和双超压结构,其中双超压结构可细分为上强下弱、上弱下强和上下均势3种类型;平面上,超压中心与洼槽沉积中心相吻合,河间和留西洼槽超压幅度最大;从沙三段到沙一段,南部洼槽区超压规模明显减小,北部洼槽区超压规模略增,超压中心具有从南到北的迁移性;东营组超压成因机制主要为欠压实作用,沙一段和沙三段的超压成因机制为生烃作用与欠压实作用的混合增压机制;由于欠压实与生烃两者对超压的贡献比例差异,造就了研究区多种超压结构并存的现状,并影响了油气的空间分布。

Characteristics and genetic mechanism of formation pressure in sags of Raoyang Depression

Using pressure data and simulation results of fluid pressure, this study analyzed the distribution of abnormal pressure and the contribution of disequilibrium compaction and hydrocarbon generation to overpressure in Raoyang Depression. The results show that overpressure is widely developed in Raoyang Depression, but the scale of overpressure varies significantly in different sags. Vertically, overpressure exists in Paleogene, including E_d, Es_1and Es₃. There are four types of overpressure structures in Paleogene, including the single pressure structure and three double overpressure structures:the upper pressure stronger than lower, lower pressure stronger than upper, and upper pressure equally close to the lower pressure. In plane, overpressure center is corresponding to the depositional center in four sags, of which Hejian and Liuxi sags developed the strongest overpressure. Overpressure centers migrate through time from Es₃ Formation to Es₁ Formation, and the overpressure scale is significantly reduced in the southern sags, while slightly increased in the northern sags. For Dongying Formation, disequilibrium compaction is the main mechanism generating overpressure, whereas for Es₁ and Es₃ Formations, both disequilibrium compaction and hydrocarbon generation are the main mechanisms. The different contribution ratio of the disequilibrium compaction and hydrocarbon generation to overpressure leads to various structures of overpressure that coexist and affect the distribution of hydrocarbons.