基于摩擦阻力系数的卡瓦闸板对连续油管夹持特性影响分析

针对连续油管作业过程中卡瓦闸板防喷器对其夹持时造成的划伤、缩颈并降低其使用寿命的问题,提出连续油管与卡瓦闸板之间摩擦阻力系数对其相互作用的影响。建立了卡瓦闸板夹持连续油管三维物理模型,基于弹塑性力学理论建立起其计算模型,以Ramberg-Osgood弹塑性模型为基础,采用数值模拟的手段分析了多种工况下不同摩擦阻力系数对连续油管最大Mises应力、轴向位移以及接触应力的影响。研究表明:适当增加摩擦阻力系数有利于减小连续油管上的应力集中,也有助于限制轴向位移避免划伤连续油管和造成卡瓦闸板崩齿,同时提高卡瓦闸板对连续油管的夹持效果。最终以屈服强度为指标,结合连续油管轴向位移量趋势变化给出摩擦阻力系数安全区间为0.4～0.6,旨在为连续油管安全作业提供参考。

Analysis of the Impact of Slip Ram on Coiled Tubing Clamping Characteristics Based on Friction Resistance Coefficient

In view of the scratches, necks and service life reduction caused by blowout preventer with slip ram during coiled tubing operation, the influence of friction coefficient between coiled tubing and slip ram on its interaction is put forward. A three-dimensional physical model of coiled tubing clamped by slip ram is established, and its calculation model is established based on elastic-plastic mechanics theory. Based on Ramberg-Osgood elastic-plastic model, the maximum Mises stress, axial displacement and contact stress of coiled tubing under various working conditions are analyzed by means of numerical simulation. The results show that increasing friction coefficient properly is beneficial to reduce stress concentration on coiled tubing, to limit axial displacement, to avoid scratching coiled tubing and cracking of slip ram, and to improve the clamping effect of slip ram on coiled tubing. Finally, taking yield strength as the index and combining with the trend change of axial displacement of coiled tubing, the safe range of friction coefficient is 0.4-0.6, which aims to provide reference for safe operation of coiled tubing.