沾化凹陷古近系地层压力分布特征及其控制因素

Distribution characteristics and its controlling factors of Paleogene formation pressure in Zhanhua sag,Jiyang depression

根据实测与计算的压力数据,对沾化凹陷古近系地层压力的分布特征进行分析,并结合构造、沉积及成岩特征研究压力分布的控制因素。结果表明:古近系纵向上发育东三段-沙一段、沙三中-下、沙四段3个异常压力系统,它们为沙二-沙三上、沙四顶部降压带所分隔;横向上存在多个与沉积洼陷中心对应的压力体系,地层压力、剩余压力和压力系数从体系中心向外降低;地层压力分布受构造、沉积和成岩作用的控制,其中构造格局通过控制沉积中心决定了压力体系中心位置,断裂卸压作用分隔压力体系;沉积间断形成的卸压带将纵向上分隔为3个异常压力体系,沉积物性决定异常压力产生深度,沉积速率大于220 m/Ma时欠压实异常压力产生,欠压实产生的异常压力与沉积速率成正比;生烃作用的影响导致异常压力层段和横向分布与烃源岩分布相一致,而蒙-伊等矿物转化对特定深度的异常压力有贡献。

According to the tested and calculated formation pressure data, the distribution pattern of Paleogene formation pressure in Zhanhua sag was investigated. Combining with tectonic, sedimentary and diagenesis information, the controlling factors of formation pressure distribution pattern were researched. The results show that there are vertically three abnormal high pressure systems named as Ed3-ES1 , Es3^ z-x, Es4 systems from the top to down, and the three pressure systems are parted by two pressure-falling zones of Es2-Es3^s and upper Es4. Horizontally, the pressure field is divided by faults and uplifts into many pressure centers （sub-field） which are consistent with sedimentary centers. The formation pressure, surplus pressure and pressure coefficient reduce from center to margin. The distribution pattern of formation pressure is controlled by tectonic, sedimentary and diagenesis processes. The tectonic pattern determines the station of formation pressure centers, and the pres- sure system is divided by faults pressure-falling action. The property of sedimentary materials determines the depth of abnormal pressure, which is related with deposition velocity. With the deposition velocity exceeding 220 m/Ma, the abnormal high pressure could appear. The abnormal pressure produced by incompaction is direct ratio to deposition velocity. Contribution of hydrocarbon generation to the abnormal high pressure results in the distribution consistent of abnormal pressure with source rocks. Translation of some minerals such as montmorillonite and illite could induce abnormal pressure in specifically depth.