疏松砂岩油藏水平井管外地层塑性挤压充填模拟

Numerical simulation of plastic compaction packing outside casing in horizontal wells in unconsolidated sandstone reservoirs

针对水平井管外地层砾石充填问题,将水平井近井地层分为弹性区、压实区和填充区,根据Mohr-Coulomb准则以及平面应变轴对称问题的基本理论,建立疏松砂岩地层高压挤注条件下的水平井管外地层塑性挤压充填模拟数学模型。模拟分析结果表明:由于沿水平井井身轨迹的岩石力学参数及地应力的非均质性,管外地层塑性挤压充填剖面也表现出较强的非均匀性;岩石强度相对较低的井段,最终挤压破坏的半径相对较大;井底施工压力较高时,水平段管外塑性挤压破坏程度沿井身轨迹的变化差异比低施工压力时更加明显;随着井底压力增高,泊松比对充填扩张率的影响可以忽略,岩石内摩擦角、内聚力和弹性模量对充填扩张率影响均较大。

For the gravel packing outside-casing in horizontal wells,the region near the wellbore can be divided into three sections,in terms of rock mechanics,namely elastic deformation,plastic compaction and gravel pack.A systematic model for high pressure plastic compaction packing was developed to predict packing area size around horizontal wells in unconsolidated sandstone reservoirs,which was based on Mohr-Coulomb rock failure law and axial symmetry plane strain theory.The numerical simulation results show that,due to the formation heterogeneity and variations of rock properties,the size and profile of the plastic compaction packing area changes greatly along the wellbore trajectory.The radius of compacting failure area increases with the rock strength decreasing.High bottomhole injection pressure can induce more serious rock failure than that of low injection pressure.As the injection pressure increases,the effect of the Poisson ratio on extension ratio of the packing can be ignored,but the influence of other factors,such as internal fraction angel,cohesive strength and elastic modulus,needs to be considered.