A Method for Ranging and Positioning Casing with High-Intensity Magnets: Simulations and Experimental Studies

Abstract

Summary Wellbores in the upper vertical section of cluster wells are typically positioned close together, resulting in a high possibility of wellbore collision accidents. In the drilling process, accurately determining the distance and bearing of the casings of adjacent production wells is key to controlling the wellbore trajectory to avoid collision accidents. In this study, a method is proposed that uses a high-intensity magnet to magnetize a close-range casing and subsequently measures the axial forces on the magnet to determine the casing distance and positioning. Based on the theoretical analysis of the magnet’s force, the boundary finite element method is used to numerically analyze the influence of the casing position on the magnet. The force on the magnet decreases exponentially with the increase in casing distance and decreases nonlinearly and rapidly as the angle increases. A method to determine the position of a casing by analyzing the forces on two adjacent magnets is proposed. Based on the fitting of the simulation results, a mathematical model that calculates the casing distance and azimuth is established. A simple experimental device was designed to verify the reliability of the numerical simulations and casing ranging and positioning of the models. The maximal calculation error of the casing distance is determined at 5 mm, and the angle error is less than 2°. Moreover, the actual measured distance is less than 1 m. The angle between the axes of the high-intensity magnets has an important influence on the distance measurement range. The following steps are suggested to improve the detection range of the casing: Improve the remanence of the high-intensity magnet; extend the length of the force arm of the force measuring mechanism; apply a high-resolution torque sensor; and set a smaller angle between the axes of the high-intensity magnets. The proposed method can achieve high-efficiency measurements and calculations of the casing distance and bearing based on a simple measurement structure and low-cost manufacturing. It also has the potential to be applied to multiple short-range casing ranging and positioning scenarios.