ABSTRACT

Hydrate formation and wax deposition in submarine pipelines hinder the transportation of oil and gas. Pigging operation is an important means to ensure pipeline flow assurance. In this paper, the idea of coiled tubing (CT) intervening in hydrate and wax removal of underwater pipeline is put forward, and the feasibility of this method is discussed from the point of view of the ultimate extension capacity of coiled tubing. To this end, theoretical analyses and experimental tests are performed on the mechanical behaviour of coiled tubing in submarine pipelines. The present paper mainly analyses the axial force transfer characteristic of coiled tubing with different sizes and the contact force coefficient values of coiled tubing with fixed and loaded end conditions under different boundary conditions. Besides, the effects of CT size and friction coefficient on the reachable depth of hydrate or wax plugs removal are also studied and the obtained maximum depth of the CT inlet is compared with the total length of the five-segment centreline of the South China Sea submarine pipelines. The results show that CT can further achieve more plug removal as the reduction of friction coefficient, while the depth of plug removal reduces with the decrease of CT size. CTs only with limited sizes can be used to complete the plug removal process in submarine pipelines.

摘要

海底管道中的水合物形成和蜡沉积阻碍了石油和天然气的运输。清管作业是保证管道畅通的重要手段。本文提出了连续油管（CT）干预水下管道水合物脱蜡的思路，并从连续油管极限延伸能力的角度讨论了该方法的可行性。为此，对海底管道连续油管的力学行为进行了理论分析和实验测试。本文主要分析了不同尺寸连续油管的轴向力传递特性以及不同边界条件下连续油管固定端和负载端条件下的接触力系数值。除了，还研究了 CT 尺寸和摩擦系数对水合物或蜡塞去除可达深度的影响，并将 CT 进口的最大深度与南海海底管道五段中心线的总长度进行了比较。结果表明，随着摩擦系数的降低，CT可以进一步实现更多的除塞，而随着CT尺寸的减小，除塞深度也减小。只能使用有限尺寸的 CT 来完成海底管道中的塞子去除过程。结果表明，随着摩擦系数的降低，CT可以进一步实现更多的除塞，而随着CT尺寸的减小，除塞深度也减小。只能使用有限尺寸的 CT 来完成海底管道中的塞子去除过程。结果表明，随着摩擦系数的降低，CT可以进一步实现更多的除塞，而随着CT尺寸的减小，除塞深度也减小。只能使用有限尺寸的 CT 来完成海底管道中的塞子去除过程。