Abstract: In the process of converting depleted oil and gas reservoirs into storage facilities, identifying and plugging complex old wells is a crucial step. Traditionally, magnetic guidance technology has been employed for locating old wells containing ferromagnetic columns. However, for open-hole wells without magnetic beacons, underground positioning often relies on imprecise well history data, leading to significant errors. Acoustic remote sensing technology, by analyzing the characteristics of acoustic wave reflections, theoretically possesses the capability to precisely locate open-hole wells through detecting and identifying abnormal geological bodies near the wellbore. This study systematically analyzed the feasibility of this technology in open-hole well detection and underground positioning operations from three aspects: acoustic field characteristics, reflection imaging features of open-hole wells, and processing and positioning of acoustic remote sensing data. We initially utilized a spatial fourth-order time second-order finite difference method (FDTD) on staggered grids to solve the elastic wave equation, simulating the propagation behavior of sound waves around the wellbore under different geological conditions. Subsequently, based on the acoustic wave reflection characteristics under actual working conditions and combined with numerical simulation results, we analyzed the reflection imaging features of open-hole wells. Finally, through processing measured data, we verified the detection range and accuracy of the acoustic remote sensing technology in practical applications. Experimental results indicate that the acoustic remote sensing technology is unaffected by external factors and can effectively locate open-hole wells at depths of 3 000 m underground, determining their exact spatial positions within formations. The detection range reaches 4~16 m, Positioning error less than ±0.5 m, suitable for abandoned well location under complex geological conditions. This study demonstrates that acoustic remote sensing technology not only overcomes the limitations of traditional positioning methods but also significantly improves the positioning accuracy of open-hole wells, playing a crucial role in the conversion of depleted oil and gas reservoirs into natural gas storage facilities. The application of this technology not only enhances the efficiency of safely plugging abandoned wells but also reduces risks caused by positioning errors. In the future, we will further optimize algorithms, expand detection ranges, and improve positioning accuracy to meet broader engineering needs.

Key words: acoustic remote detection, barehole well, numerical simulation, magnetic detection technology, underground positioning