Energy Flow Domain Reverse-Time Migration for Borehole Radar

A modified 2-D reverse-time migration algorithm in the energy flow domain, called EF-RTM, is proposed for short impulse borehole radar (BHR) imaging. The key of the approach is based on Poynting's theorem, which allows decomposition of the energy flux density (EFD) derived from the source and receiver wave fields in different wave-propagation directions. Then, imaging conditions, for example, zero-lag cross correlation (prestack migration) and zero-time imaging principle (poststack migration), are applied to the decomposed EFD-field components to obtain the migrated sections. The characteristics of the resulting images can be optionally combined or separately used for better BHR data imaging, interpretation, and analysis. In this paper, the EF-RTM algorithm is validated by numerical modeling and real field data and compared with the conventional RTM algorithm. All the results show that this new EF-RTM method is superior to the conventional RTM method: it inherits the high precision of RTM with additional imaging advantages, such as natural wave-field decomposition in different directions, improved migrated cross-range resolution, a better focus of the target's shape, and migration noise reduction.