3-D Imaging Method for Directional Borehole Radar Combining Migration and Radon Transform

Abstract

In engineering investigation and energy exploration, accurately characterizing the spatial distribution of geological bodies is essential for ensuring construction safety and efficient resource utilization. As an important branch of borehole radar, directional borehole radar (DBR) enables 3-D reconstruction of geological targets under single-borehole conditions. However, existing 3-D imaging algorithms for DBR are mainly designed for simple targets, and their performance remains limited in complex environments, which restricts further development and application of this technology. To address this issue, we propose a 3-D imaging method that combines migration and the Radon transform and introduces the concept of transform-domain direction of arrival (DOA) estimation. The method first applies migration to separate overlapping diffraction waves and then employs the Radon transform to further process residual overlapping wavefields. Subsequently, the DOA estimation is performed: point targets such as cavities are processed in the migration domain, while planar targets such as fractures and faults are processed in the Radon domain, thereby obtaining accurate azimuth information and achieving 3-D reconstruction under complex multitarget conditions. Numerical simulations and field data demonstrate that the proposed method improves DOA estimation accuracy, enhances multitarget imaging performance, and strengthens the capability of DBR in complex subsurface environments, providing a powerful tool for high-resolution geophysical exploration.