流固耦合作用下注水井井壁稳定性研究

注水开发油田在生产过程中，渗流场会对油藏地应力场产生影响，在井壁附近产生应力集中。研究了注水过程中流固耦合作用下套管损坏的力学机理，在传统的Biot 方程的基础上，考虑介质渗透性能随应力的变化，建立了注采过程中流体渗流与固体弹塑性变形的非线性耦合数学模型，采用全耦合的有限元法对所建立的模型进行求解。通过对大庆油田南二区某注水井注水开发过程的数值模拟，分析了注水对储层孔隙压力、井壁围岩应力场和变形场的影响，并对比了不同注采情况下储层孔隙压力和井壁应力随时间的变化关系。研究表明，油藏注水开采过程中，油藏流固耦合作用对地层特别是井壁附近围岩的应力和变形影响很大。研究结果为合理建立油藏注水开发的流固耦合计算模型，合理控制注采压差，预防和减少该地区地层变形、套管损坏等提供了依据。

Borehole stability study of water injection wells in fluid-solid coupling

During the production process of water injection oilfield, in-situ stress field is influenced by seepage field, leading to stress concentration near the borehole.This paper studies the mechanical mechanism of casing damage in fluid-solid coupling during water injection.Based on conventional Biot equation, considering the medium permeability change with ground stress, the paper develops a nonlinear coupling mathematical model for fluid seepage and solid elastic-plastic deformation during injection-production process.The model is solved with full-coupled finite element method.In addition, through numerical simulation for injecting process of a water injection well in Nan'er zone of Daqing Oilfield, the paper analyzes the effect of water injection on pore pressure, the stress field and deformation field of the rock around the borehole.Relationship of reservoir pore pressure and borehole stress with time is also contrasted under different injection-production conditions.Simulation results show that fluid-solid coupling in water injection reservoirs has great influence on stress field and deformation field of borehole rock.The results are very helpful to develop fluidsolid coupling mathematical model during water injection development, control optimum injection-production pressure difference and prevent or mitigate the casing damage in oil field.