断层滑移条件下页岩气井套管变形影响因素分析

Analysis of Influencing Factors of Shale Gas Well Casing Deformation Based on Fault Slip

目前,中国四川盆地页岩气区水平井多级压裂过程中的套管变形问题日益突出,导致桥塞无法顺利下入,丢段现象突出,严重影响页岩气的高效开发。研究表明,断层滑移剪切套管是造成套管变形失效的主要因素之一,而断层滑移对套管变形量的影响规律有待进一步理清。为研究上述问题,建立了断层界面滑移下的井筒变形数值模型,分析了断层滑移条件下套管变形量及相关影响因素。结果表明:地层滑移量与套管变形量间基本呈线性正关系;断层夹角即滑移界面与井筒的夹角对套管变形量影响明显,当夹角为90°时套管变形量最大;低弹性模量水泥环对套管的保护更为有利;通过优选与井眼相配合的套管尺寸有利于缓解套管变形问题。断层滑移条件下套管变形量的计算模型对于中国页岩气井套管变形问题的缓解可以奠定理论基础。

The casing deformation problem in the multi-stage fracturing process of horizontal wells in the Sichuan basin shale gas field becomes increasingly prominent.The fracturing tool cannot be placed in the specified position when the casing deformation occurs.The fracturing operation aslo cannot be completed smoothly as designed.The efficient development of shale gas is affected by casing deformation.The fault slip and shear casing are considered by scholars to be one of the main factors causing casing deformation,and the law of the influence of fault slip on casing deformation needs to be further clarified.In order to study the above problems,a numerical model of wellbore deformation under fault interface slip was established,and casing deformation under fault slip conditions and related influencing factors were analyzed.The results show that the relationship between formation slippage and casing deformation is basically linearly positive.The included angle of the fault,that is,the angle between the slip interface and the wellbore,has a significant effect on casing deformation.When the angle is 90°,the deformation of the casing reaches the maximum value.The low elastic modulus cement ring is more beneficial to the protection of the casing.By optimizing the casing size matched with the wellbore,it is helpful to alleviate the casing deformation problem.The calculation model of casing deformation under fault slipping can lay a theoretical foundation for the prevention of casing deformation in shale gas wells in China.