Design and Application of a Mechanical Double-Positioning Block Casing Collar Locator

Due to the problems of pre-bending and force-induced length change occurring in the course of running in hole with coiled tubing,it is not possible to satisfy the requirements of coiled tubing fracturing technology for high-precision positioning of the target layer.For this reason,a casing collar locator with mechanical double positioning blocks was designed.After analyzing the advantages/disadvantages of existing casing collar locator,the structure of casing collar locator with mechanical double positioning blocks was determined.The team analyzed the stress change on the locator in five cases while running it in the hole,considering the working principle of the locator,i.e.achieving the precise positioning of the target zone by means of two mechanical fluctuations generated by the positioning blocks passing through casing collar,in conjunction with hook load variation and logging data.ADAMS software was used to numerically simulate the dynamics of this locator,and analyze the influences of the positioning block angle,spring stiffness and positioning block height difference on the mechanical fluctuations of this locator.The simulation analysis found that the positioning block angle and spring stiffness were proportional to the mechanical fluctuation value,and the height difference of locating block has little influence on the mechanical fluctuations.According to the simulation results,the positioning block angle of 65° and the spring stiffness of 220 N/mm were selected,by which a test prototype was manufactured and applied in the well X of Tahe Oilfield.The application results showed that the locator could detect and distinguish among the disturbance fluctuations caused by vibration,solid particles and the mechanical fluctuations that were generated by passing through casing collar,so as to avoid misjudgment.The research suggested that the designed casing collar locator with mechanical double positioning blocks had high positioning precision and could effectively solve the problems of inaccurate positioning on the target layer while running coiled tubing in the hole.