流线数值模拟中的无效网格处理方法

Treatment Method of Immobile Grid in Streamline Numerical Simulation

对于砂体横向连续性差,呈透镜状,局部区域为局部断层影响的水动力滞留区或泥岩的油区进行数值模拟时必然涉及到不可流动区域的处理,不可流动区域网格化后变为不可流动网格,又称无效网格或死网格。不可流动区域的存在会影响流线数值模拟的压力场计算以及流线追踪过程,导致流线数值模拟失败,因此无效网格的研究对流线数值模拟计算具有重要意义。无效网格的处理方法主要有三种:直接计算法、镜像反映法及网格设置法,还有流线追踪、流线饱和度模型中涉及到的无效网格处理方法。通过实例计算分析,证明了无效网格处理方法的有效性。网格设置法具有良好的规律性,计算简便;直接计算法的方程系数矩阵规律复杂;镜像反映法要不断对无效网格重新赋值,影响计算速度。当模拟区存在不可流动区域时,无效网格处理方法能有效地解决流线数值模拟过程中出现的问题。

For oildoms with poor lateral continuity of sand body shown as a lentoid in lateral distribution,hydrodynamic retention area caused by fault or shale in local area,it is necessary to treat non-flowable areas in numerical simulation.The non-flowable areas will become non-flowable grids,also known as immobile grids or dead grids after be gridded.Presence of non-flowable areas can affect pressure filed calculation and streamline tracing process in streamline numerical simulation,which will lead to failure of such simulation.So it is important to study the dead grids.Introduced are such three methods for treating non-flowable grids in differential process as direct calculation method,'mirror image' method and grid setting method.The grid setting method has such advantages as good regularity and simple calculation and better than the others.Example calculation and analysis results show that such method is effective.In the case of non-flowable areas existing in simulation area,the grid setting method can solve problems effectively occurring in streamline numerical simulation.