Numerical simulation study of the sonic detection and imaging methods for fish top in downhole environments

To address the difficulty and low efficiency of fishing and docking fractured drill tools in deep and ultra-deep wells, a line-array scanning method using acoustic transducers was employed to generate images of the fish top. Based on borehole acoustic theory, a casing-fish annulus space model was established. The acoustic wave propagation characteristics and one-dimensional linear array receiving properties were studied, with reflection echoes serving as the evaluation index. Key parameters such as sound source frequency, detection distance, fish wall thickness, and array spacing were analyzed in detail. Effective strategies to enhance sound wave transmission distance and image quality were discussed. Acoustic imaging results for a Ø244.5 mm casing and Ø127.0 mm drill pipe indicated that the horizontal section image error relative to the true center of the fish was 11.7%, while the error between the image center and the true center of the fish top was 2%. For inclined sections, The image of the fish revealed the inclined orientation. The findings indicated that acoustic imaging of the fish top was achieved using fewer acoustic transducers, providing a novel solution for enhancing fishing efficiency and serving as a valuable reference for future research on downhole tools and systems.