Uncertainty analysis for hydraulic cylinder pressure calculation of orienter in coiled tubing drilling

Orienter working pressure for coiled tubing drilling (CTD) is associated with the randomness of torque. Thus, a new method for orienter pressure design was built based on uncertainty analysis theory. The Monte-Carlo method was applied to simulate the distribution of torque parameters. The distribution types and functions of torque were obtained. Based on the functional relationship between the hydraulic cylinder working pressure and the friction torque, the probability distribution of working pressure was obtained with the probability theory. The control variable method was adopted to analyze the range of the hydraulic cylinder working pressure. Results show that working pressure is not a single value but an interval with cumulative probability change. The higher the confidence level, the narrower the pressure range, conversely, the wider the pressure range. The larger the mean square deviation, the wider the pressure range. With this new method, working pressure range of the orienter is obtained from 3.93 to 11.71 MPa, Uncertainty analysis method can overcome the disadvantages of traditional method and provide more accurate references for hydraulic cylinder design of orienter in CTD.