江汉平原震旦系储层古水动力场演化及其与油气运聚的关系

Relation between palaeohydrodynamic field evolution and hydrocarbon migration and accumulation of Sinian reservoirs in Jianghan Plain

根据江汉平原构造运动的多期性、沉积与剥蚀作用和水动力条件,把震旦系储层地下径流演化过程划分为加里东期(Ⅰ)、海西—早印支期(Ⅱ)、晚印支—早燕山期(Ⅲ)、晚燕山—喜马拉雅期(Ⅳ)4个水文地质旋回,恢复和重建了古水动力场。根据储层水动力场态势以及地下水径流汇聚特点,提出了有利于油气聚集的水动力学模式:低势圈闭型、低势半圈闭型、势梯度陡变型与台缘型和流势马鞍型。对储层古水动力场的剖析表明,震旦系储层在第Ⅰ—第Ⅱ水文地质旋回时期的地下水动力特征具有明显的继承性;在第Ⅲ水文地质旋回时期,伴随着构造运动,震旦系储层地下水动力场开始发生变化;在第Ⅳ水文地质旋回时期,反转、拉张、滑脱、褶皱等构造变动导致震旦系储层地下水动力场发生了巨大变化,在区域性分水岭两侧出现了有利于油气储存的区块。

According to the multiphase tectonic activity,deposition,denudation and hydrodynamic condition of Jianghan Plain,the evolution progress ofgroundwater flow in Sinian reservoirs has been divided into four hydrogeologic cycles: Caledonian cycle( Ⅰ ),Hercynian-Early Indo Chineseepoch cycle( Ⅱ ) ,Late Indo Chinese epoch-Early Yanshan cycle( Ⅲ ),Late Yanshan-Himalayan cycle( Ⅳ ) ,and the palaeohydrodynamicfield was rebuilt. According to the situation of the palaeohydrodynamic field and the collective characters of the groundwater flow,the hydro-dynamic models favorable to oil and gas accumulation were built. These models include low-potential trapped,low-potential half trapped,suddenly changed potential gradient,plateau-edge and saddle shaped fluid potential types. Ancient hydrodynamic field of reservoir analysisshows that:the groundwater dynamics has clear successor of Sinian reservoirs in section Ⅰ-Ⅱ hydrogeological cycle periods. In section Ⅲhydrogeological cycle period,accompanied by tectonic movement,the groundwater hydrodynamic field of Sinian reservoir began to mutate. Insection Ⅳ hydrogeological cycle period,inversion,extension,detachment,folding,and some other tectonic disturbances led to tremendouschanges in the groundwater hydrodynamic field of the Sinian reservoirs,and the zones at both sides of the regional watershed are favorable tooil and gas reservoir.