透镜状砂岩油藏成藏过程数值模拟 ——以东营凹陷牛35-B砂体为例

为了对透镜状砂岩油藏的成藏机理进行深入研究,利用可压缩多孔介质油水两相渗流的基本原理,对东营凹陷牛35-B砂岩油藏的成藏过程进行了二维数值模拟。模拟考虑了砂体区地层沉积(剥蚀)、地层厚度变化、岩石孔渗条件变化、流体物性变化、毛管压力、相对渗透率、油气生成等一系列过程和参数。模拟再现了石油在砂体中聚集的过程,模拟得到的最终含油饱和度及其分布与现实情况基本吻合。模拟和分析结果表明,围岩和砂体的毛管压力差异是驱动石油在类似牛35-B这样的透镜状砂岩油藏中聚集的根本动力,而这一驱动力是由于围岩和砂体物性上的差异以及石油生成两种因素结合在一起而形成的。

Numerical simulation of oil-trapping process of lenticular sand reservoir ——a case from Niu 35-B sand reservoir of Dongying depression

In order to thoroughly study the oil accumulation mechanism of lenticular sand reservoirs,the oil-trapping process of Niu 35-B sand reservoir of Dongying depression was numerically simulated on 2-D condition based on the theory of two-phase fluid flow in compactable porous media.The various related processes including sedimentation/denudation,variations of strata thickness,porosity and permeability of rock,physical properties of fluids,and the parameters such as capillary pressure,relative permeability and oil generation were considered in the simulation.The oil accumulation process in the reservoir reappears in simulation,and the simulated oil saturation and distribution agree well with the real situation.The results show that the fundamental driven force for oil accumulating in lenticular sand reservoir as Niu 35-B is the capillary pressure difference built up between the source rock and reservoir,and the driven force forms from the combination of the difference of the physical properties between source rock and reservoir and the oil generation.