海上油气井服役过程中隔水导管旋转原因分析

海上生产井在服役过程中井口发生旋转会对采油树、井口管汇以及油气生产带来严重的安全隐患和作业风险。针对海上某油田在服役多年后井口发生的旋转现象，从最外层隔水导管受力情况分析出发，对钻完井作业过程和生产过程中的各个阶段影响因素进行了分析，建立了钻井隔水导管在海流作用下产生扭矩的力学模型；考虑到油气井长期服役后隔水导管外侧会附着大量海生物现象，附着的海生物在海流作用下会对隔水导管产生更大的扭力，从而引起隔水导管的旋转。通过理论分析和有限元计算，建立了不同海生物附着条件下隔水导管旋转力的计算模型。利用建立的钻井隔水导管旋转力计算模型进行案例分析，进一步验证了理论模型的正确性和准确性。研究结果能够为海上隔水导管扣型设计、隔水导管连接方式和油气井服役过程中井口维护提供理论依据。

Cause analysis on the rotation of riser during the operation of offshore oil and gas wells

The rotation of well in the service process of offshore production wells will bring potential safety hazard and serious operation risk to production tree, well manifold and oil & gas production. The rotation of well in a certain offshore oilfield which had been in service for many years was taken as the research object. Firstly, the influential factors in each stage of drilling and production process were analyzed with the stress analysis on the outer riser as the beginning point, and the mechanical model for the torque of the riser under the action of the ocean current was established. Then, considering that marine organisms will attach to the outside of the riser after long-term service of oil and gas wells and the attachment of marine organisms will produce greater torsion under the action of the ocean current, resulting in the rotation of the riser, the model for calculating the rotation force of the riser under different attachment conditions of marine organism was established by means of theoretical analysis and finite element calculation. Finally, the calculation model was used for case study to verify the correctness and accuracy of the theoretical model. The research results can provide theoretical basis for the buckle type design of offshore riser, the connection mode of riser and the well maintenance in the service process of oil and gas wells.