Modeling and simulation analysis of an oil tubing coupling detector based on the LVDT method

Automated drilling is one of the oil industry’s most important innovation targets. Tubing coupling detection is a crucial key component in the automation process of workover operations, by accurately detecting the position of a tubing coupling in real time, this brings convenience for operating stuff to control or provides preconditions for automatic control.  In this paper, a tubing coupling detector that is designed based on linear variable displacement transformer (LVDT) principles has been proposed to meet the requirement of accurately detecting and identifying the position of the tubing coupling during workover operations. The tubing coupling contains 3 coils that are wound on a tube or inner layer pipe and an outer casing, wherein a tubing string and a tubing coupling can penetrate through. The middle coil or primary coil is excited by an alternating voltage and the other two coils (secondary coils) detects the induced electromotive force as the tubing string passes by, the difference in the resultant electromotive force from the two secondary coils can aid in determining the position of the tubing coupling. Ansys Maxwell software is used to analyse the feasibility of this tubing coupling detection detector by analysing the induced output voltage in the secondary coils (detection coils). The simulation results shows that the proposed coupling detection device can be used to detect the position of the tubing coupling position.