台北凹陷地下水动力特征及其对油气运移和聚集的影响

吐哈盆地台北凹陷现今为重力水流盆地。台北凹陷可划分为胜北洼陷和丘东 -小草湖洼陷两个地下水流系统。区域地下水流向自北向南,北部山前构造带为地下水补给区,南部中央断裂带北缘为地下水排泄区。垂向上,地下水的连通性较好。台北凹陷自侏罗纪以来,经历了三个不同的地下水动力演化阶段。早期 (早侏罗世 -晚侏罗世 )为压实水流阶段,该阶段导致区内较大规模的油气藏均分布在生烃洼陷周围,有效烃源岩展布范围之内;中期 (早白垩世 -第三纪中新世 )为压实水流 -重力水流阶段,该阶段对早期形成的油气藏进行改造和调整,并在压实水流与重力水流的混合带形成油气藏;晚期 (第三纪上新世至今 )为重力水流阶段,它导致沿区域地下水流运移方向,油水界面、油气藏充满度和含油气层段均发生明显的变化。

Hydrodynamic Characteristics and Its Effect on Oil-Gas Migration and Accumulation in Taibei Depression,Tu-Ha Basin

The regional groundwater flow in Taibei depression of Tu-Ha basin is the gravity-induced cross-formational groundwater flow. There are two gravity-induced cross-formational groundwater flow systems in Taibei depression. One is in Shengbei sag and the other is in Qiudong and Xiaocaohu sags. The groundwater in the groundwater systems flows from north to south. The recharge area of the groundwater is in the Bogeda mountainous terrain north Taibei depression and the drainage is in the north border of the central faulted zone in Taibei depression. There is vertically good hydraulic connection among the different formation waters. Since the Jurassic period,there have been three different stages of the groundwater hydrodynamic evolution. The early stage (Jurassic period) is the stage of the compacted groundwater flow,in which the compacted flow caused the large-scale oil-gas reservoir to distribute within effective source rocks around the sags of the generating hydrocarbon. In the middle stage(Cretaceous Period-Miocene Epoch),the groundwater flow is the compacted and gravity-induced flow and it had adjusted the reservoir formed in the early stage of hydrodynamic evolution. The groundwater caused oil and gas to accumulate in the mixed zone of the compacted and gravity-induced groundwater flows. In the late stage(Pliocene Epoch to now),the ground water flow is driven by topography and it had the interface of oil/water,theoil saturation of reservoir and the oil-gas-bearing formation and location changed significantly along regional groundwater flow.