Analysis Of Coiled Tubing Running Length Considering Residual Bending And Research On Vibration Drag Reduction Method

The initial residual bending of coiled tubing before entering the well increases the friction in the process of running in and limits the operation of coiled tubing.In order to solve this problem,theoretical analysis of coiled tubing with residual bending and vibration drag reduction are carried out.First of all,the process of coiled tubing running in and running out is analyzed,and the reason for the residual bending of coiled tubing before entering the well is obtained,and it is proved by calculation that there is residual bending of coiled tubing before entering the well;The coiled tubing running in test and field measurement are carried out,and the actual measured residual bending radius of 2-inch QT-900 series coiled tubing is 6433.33 mm,it is verified that the coiled tubing has residual bending before entering the well.Secondly,the residual bending is introduced into the total potential energy formula to deduce,a new calculation model of coiled tubing running length is established,and the influence of residual bending on the running length of coiled tubing is analyzed.The results show that the residual bending can significantly reduce the maximum running in length of coiled tubing.When the residual bending radius is 6463 mm,the theoretical value of the maximum running in length of horizontal section of coiled tubing with residual bending is 1658 m,which is 29% less than that without residual bending.According to the field test data of a well in Mahu,Xinjiang Oilfield,when the running length of the coiled tubing in the horizontal section is 1604 m,the spiral locking occurs,with an error of 3.26% compared with the theoretical value deduced by the formula.Finally,aiming at the problem of coiled tubing spiral locking,the power joint of the hydraulic oscillation drag reducer of coiled tubing is designed,and the unsteady numerical simulation is carried out,the mechanism of vibration drag reduction is analyzed,the fluid structure coupling modal analysis and the single factor analysis of pulse pressure are carried out.The results show that the pulse pressure produced by the periodic wall attached deflection of the main jet in the oscillating cavity acts on the oscillating short section,which causes the axial vibration of the pipe string.The greater the vibration speed of the pipe string,the better the drag reduction effect;The pulse pressure causes the larger strain in the oscillating cavity of the power joint,which should be treated with nitriding and carburizing to extend the service life,and the rationality of the structural design is verified;With the increase of the inlet velocity,the pulse pressure amplitude shows an increasing trend;With the increase of the angle between the walls,the pulse pressure amplitude shows a trend of first increasing and then decreasing.When the angle between the walls is 27.5°,the maximum pulse pressure amplitude is 0.14 MPa;With the increase of the diameter of the feedback channel,the pulse pressure amplitude decreases first and then increases.When the diameter of the feedback channel is 12 mm,the minimum pulse pressure amplitude is0.02 MPa.In order to improve the effect of drag reduction,we can increase the inlet velocity,and use the power joint with the angle of 27.5° and the diameter of feedback channel 16 mm to generate more pulse pressure.