大量实验表明:当油藏生产原油时,随着地层中流体压力的降低,油层的孔隙度和渗透率下降,特别是在异常高压油藏中尤为显著。数据表明多孔介质的孔隙度和渗透率随压降的变化规律是指数关系,而实际的油藏介质变形是弹塑性的,即变形在流体压力恢复后,变形不可能完全恢复,因此在开发前期一定要注意保持一定的地层压力。从流体和多孔介质的本构方程出发,建立液体在变形介质油藏中渗流的微分方程。用解析的方法得到了变形介质中的定常流动的精确解;并用数值模拟的方法,研究了无限大油藏、封闭油藏和边水油藏中的不稳定压力,绘制了相应的井底压力曲线。最后分析了封闭变形介质油藏中,定压生产时,油井的产量变化。研究表明:在异常高压的油藏中,必须考虑由介质变形引起的孔隙度和渗透率的影响。
Many experiments show that: when a well produces oil from a reservoir, the porosity and permeability will decrease, as fluid pressure drops, especially for reservoirs with abnormal high pressure. Data show that the change laws of porosity and permeability are exponent of pressure drop. And the media deformation is elasticity-plasticity deformation process, so the pressure must be kept above one certain level in reservoirs with deformable media during the early stage of exploitation. From the constitutive equation of fluid and solid media, the differential equation of percolation is derived. Using numerical computation method , some percolating situations are analyzed, and some typical well testing curves are gotten in a assumed infinity reservoir.water lateral boundary reservoir and sealed boundary reservoir. Finally the well production in deformable reservoir with sealed boundary at constant well-bore pressure is discussed. The results show that the influence of media deformation must be considered in reservoirs with abnormally high pressure.