油井开采过程中油层变形的流固耦合分析

THE FULLY COUPLED FLUID-SOLID ANALYSIS FOR THE RESERVOIR ROCK DEFORMATIONS DUE TO OIL WITHDRAWAL

在油气开采过程中 ,随着油气的不断采出 ,必然造成孔隙流体压力的逐渐降低 ,由此导致储层岩石骨架的有效应力增大 ,使得油层产生变形或压实。当油层产生变形或压实时 ,对油气生产将造成不利影响。比如 :使得油藏的渗透率降低 ,继而使油井的产能降低 ,同时 ,油层的变形直接影响着油井和套管的变形与破坏等等。油气开采过程中油层的变形可以描述为三维变形场与三维流体流动场的耦合问题 ,利用可变形多孔介质中流体渗流的流固耦合有限元数值模型 ,对该问题进行了数值模拟 ,获得了几个很有价值的结论 ,可以用来解释一些现场生产实际中出现的问题。

The effective normal stress in a hydrocarbon reservoir will increase as a result of the decline in pore fluid pressure associated with the withdrawal of fluids,thus leading to a compaction or deformation of the reservoir rocks,with a consequent decrease in permeability and production,and a failure of the oil wells and the casings,and sometimes subsidence of the ground surface.The reservoir rock deformation due to fluid tapping can be described by a general 3 D deformation field coupled with a 3 D fluid flow field.A finite element numerical model for a fluid flow in a deforming porous medium is here presented to simulate the response of an oil reservoir subject to fluid withdrawal wherein axisymmetric flow and deformation occur simultaneously.A few useful conclusions are obtained and can be used to explain the practical problems encountered during oil production.