基于三维模型的开窗侧钻水泥环胶结强度分析

Analysis of Cementing Strength of Sidetracking Cement Sheath Based on 3D Model

在老井开窗侧钻过程中,钻头会破坏原有套管和水泥环结构,同时开窗位置附近的第一、第二胶结面胶结强度也会变化,胶结强度的下降将直接影响开窗侧钻的安全进行。为了保证开窗侧钻的安全进行,以开窗侧钻老井为研究对象,采用有限元方法建立了套管-水泥环-地层三维模型,分析了开窗侧钻过程中水泥环胶结强度变化情况。计算结果显示:开窗侧钻后第一胶结面的失效区域为开窗侧钻点上方1.60 m到下方4.00 m,其中开窗侧钻点上方0.20 m到1.65 m下方之间的胶结面环向完全失效;水泥环的失效区域为开窗侧钻点上方1.80 m到下方3.95 m,第二胶结面的失效区域为开窗侧钻点上方1.90 m到下方4.10 m。通过对轴向和环向胶结强度的分析可以得到开窗侧钻过程中胶结面的胶结强度变化规律,从而使新套管悬挂位置更加经济和安全。

During sidetracking in old wells,the drill bit may destroy existing casings and cement sheaths,and meanwhile,the cementing strength of the first and second cementing surfaces near the window will be decreased,which will affect the safety of sidetracking directly.In order to ensure the practice safety,taking a sidetracking old well as the study object,a 3 D model of casing-cement sheath-formation was established by use of the finite element method to analyze the variation of cementing strength of cement sheaths during sidetracking.The calculation results show that,after sidetracking,the failure area for the first cementing surface is from 1.60 m above the sidetracking point to 4.00 m below the sidetracking point,in which the cementing surface between 0.20 m above the sidetracking point and 1.65 m below the sidetracking point fails completely in circumferential direction.The failure area for cement sheaths ranges from 1.80 m above the sidetracking point to 3.95 m below the sidetracking point,and the failure area for the second cementing surface ranges from 1.90 m above the sidetracking point to 4.10 m below the sidetracking point.