Shallow diffraction imaging in a cross-well configuration

In this study, a new approach to shallow voids imaging is presented. Using a specifically designed cross-well SH-waves survey, we show that diffracted S waves from voids are clearly discernible and can be used for imaging. Such imaging requires an application of a model-based, automatic muting function whose goal is to prevent migration of the direct waves into the image. We apply such a function and migrate the data to the depth imaging offset domain, where the gathers' flatness is measured. These migrated gathers are sensitive to both imaging location and used velocity model, whose quality can be estimated. We demonstrate the applicability and limitations of this method for void imaging on both synthetic data and a field example we conducted.