To address the challenges associated with difficult casing running,limited annular space,and poor cementing quality in the completion of ultra-deep wells,the extreme line casing offers an effective solution over conve...To address the challenges associated with difficult casing running,limited annular space,and poor cementing quality in the completion of ultra-deep wells,the extreme line casing offers an effective solution over conventional casings.However,due to its smaller size,the joint strength of extreme line casing is reduced,which may cause failure when running in the hole.To address this issue,this study focuses on the CST-ZTΦ139.7 mm×7.72 mm extreme line casing and employs the elastic-plastic mechanics to establish a comprehensive analysis of the casing joint,taking into account the influence of geometric and material nonlinearities.A finite element model is developed to analyze the forces and deformations of the extreme line casing joint under axial tension and external collapse load.The model investigates the stress distribution of each thread tooth subjected to various tensile forces and external pressures.Additionally,the tensile strength and crushing strength of the extreme line casing joint are determined through both analytical and experimental approaches.The findings reveal that,under axial tensile load,the bearing surface of each thread tooth experiences uneven stress,with relatively high equivalent stress at the root of each thread tooth.The end thread teeth are valuable spots for failure.It is observed that the critical fracture axial load of thread decreases linearly with the increase of thread tooth sequence.Under external pressure,the circumferential stress is highest at the small end of the external thread,leading to yield deformation.The tensile strength of the joint obtained from the finite element model exhibits a relative error of less than 7%compared to the analytical and experimental values,proving the reliability of the finite element model.The tensile strength of the joint is 3091.9 k N.Moreover,in terms of anti-collapse capability,the joints demonstrate higher resistance to collapse compared to the casing body,which is consistent with the test results where the pipe body experiences collapse and failure while the joints remain intact during the experiment.The failure load of the casing body under external collapse pressure is 87.4 MPa.The present study provides a basic understanding of the mechanical strengths of extreme line casing joint.展开更多
水平井造斜段套管受弯曲、剪切和挤压等载荷共同作用,受力条件复杂多变,常发生错断或挤毁等安全事故。为此,根据水平井造斜段套管井眼轨迹的几何特性,考虑弯曲、剪切和挤压联合作用,建立造斜段套管力学模型,应用拉梅厚壁筒理论和第四强...水平井造斜段套管受弯曲、剪切和挤压等载荷共同作用,受力条件复杂多变,常发生错断或挤毁等安全事故。为此,根据水平井造斜段套管井眼轨迹的几何特性,考虑弯曲、剪切和挤压联合作用,建立造斜段套管力学模型,应用拉梅厚壁筒理论和第四强度理论,导出水平井造斜段套管抗挤强度公式。应用公式计算了不同井眼曲率、不同壁厚2种套管的抗挤强度,并进行了ANSYS有限元验证。分析结果表明:每25 m井眼曲率由3.75°增加到15.00°,P110套管的抗挤强度下降约53%,TP140套管的抗挤强度下降约28%;每25 m井眼曲率为3.75°时,φ139.7mm×12.7 mm P110套管的抗挤强度为89.8 MPa,比φ139.7 mm×10.54 mm P110套管大27%。随着井眼曲率的增加,弯曲套管的抗挤强度降低明显。研究结果可为提高水平井造斜段套管的安全性提供参考。展开更多
基金financially supported by National Natural Science foundation of China(Grant No.52104006)Science and Technology Cooperation Project of the CNPC-SWPU Innovation Alliance(Grant No.2020CX040202)。
文摘To address the challenges associated with difficult casing running,limited annular space,and poor cementing quality in the completion of ultra-deep wells,the extreme line casing offers an effective solution over conventional casings.However,due to its smaller size,the joint strength of extreme line casing is reduced,which may cause failure when running in the hole.To address this issue,this study focuses on the CST-ZTΦ139.7 mm×7.72 mm extreme line casing and employs the elastic-plastic mechanics to establish a comprehensive analysis of the casing joint,taking into account the influence of geometric and material nonlinearities.A finite element model is developed to analyze the forces and deformations of the extreme line casing joint under axial tension and external collapse load.The model investigates the stress distribution of each thread tooth subjected to various tensile forces and external pressures.Additionally,the tensile strength and crushing strength of the extreme line casing joint are determined through both analytical and experimental approaches.The findings reveal that,under axial tensile load,the bearing surface of each thread tooth experiences uneven stress,with relatively high equivalent stress at the root of each thread tooth.The end thread teeth are valuable spots for failure.It is observed that the critical fracture axial load of thread decreases linearly with the increase of thread tooth sequence.Under external pressure,the circumferential stress is highest at the small end of the external thread,leading to yield deformation.The tensile strength of the joint obtained from the finite element model exhibits a relative error of less than 7%compared to the analytical and experimental values,proving the reliability of the finite element model.The tensile strength of the joint is 3091.9 k N.Moreover,in terms of anti-collapse capability,the joints demonstrate higher resistance to collapse compared to the casing body,which is consistent with the test results where the pipe body experiences collapse and failure while the joints remain intact during the experiment.The failure load of the casing body under external collapse pressure is 87.4 MPa.The present study provides a basic understanding of the mechanical strengths of extreme line casing joint.
文摘水平井造斜段套管受弯曲、剪切和挤压等载荷共同作用,受力条件复杂多变,常发生错断或挤毁等安全事故。为此,根据水平井造斜段套管井眼轨迹的几何特性,考虑弯曲、剪切和挤压联合作用,建立造斜段套管力学模型,应用拉梅厚壁筒理论和第四强度理论,导出水平井造斜段套管抗挤强度公式。应用公式计算了不同井眼曲率、不同壁厚2种套管的抗挤强度,并进行了ANSYS有限元验证。分析结果表明:每25 m井眼曲率由3.75°增加到15.00°,P110套管的抗挤强度下降约53%,TP140套管的抗挤强度下降约28%;每25 m井眼曲率为3.75°时,φ139.7mm×12.7 mm P110套管的抗挤强度为89.8 MPa,比φ139.7 mm×10.54 mm P110套管大27%。随着井眼曲率的增加,弯曲套管的抗挤强度降低明显。研究结果可为提高水平井造斜段套管的安全性提供参考。
