连续油管的工作能力计算

Computation of the Operation Ability of Coiled Tubing

连续油管的刚度小 ,在承受纵向压力载荷时易发生正弦形、螺旋形弯曲 (失稳 ) ,因而难以承受有效的压力载荷 .讨论了连续油管在受压缩载荷时发生正弦和螺旋形弯曲的条件 ;建立了任意井眼轨迹时连续油管受力模型 ,提出了起升、下放作业时的力边界条件 ,从而可以确定连续油管的作业能力 .它包括是否可以下达预定井底并以期望的作业力进行作业 ,确定连续油管各点的受力大小和方向以判断该作业是否安全 .如果靠简单下放连续油管在井底不能实现预定作业力 ,则应使用加力器并在连续油管内部打压 ,采用迭代法求解 .同时 ,给出了简单下放和下放打压的计算实例 。

The stiffness of coiled tubing (CT) is poor. When it bears longitudinal compressive load, coiled tubing is easy to bend into sine curve or helical curve, which is called as destabilization. The destabilizing conditions of coiled tubing are discussed. The mechanical model of the coiled tubing in the hole of arbitray track is established, and its boundary conditions in trip out and trip in operations are presented. According to these, it can be determined whether the coiled tubing can reach to the expected position in wellbore and exert the force designed for completing the desired work, and the magnitude and direction of the forces borne by the coiled tubing are also calculated to determine whether its well service operation is safe. If the forces designed for the operation can not be obtained only by the weight of the coiled tubing, a power pusher and a pump are required in order to supply high pressure liquid into CT. The numerical solution in this case can be obtained by iteration method. Two examples are given in the two cases, and the calculated results are identical with the measured ones.