Dipole Shear Imaging behind casing: Extending the Borehole Acoustic Imaging envelope to Brown-fields

The potential for imaging bed boundaries and fractures using the borehole acoustic reflection survey (BARS) technique is well documented. Traditionally, this type of imaging has been conducted with a monopole source and imaging the reflected P and the mode-converted transmission waves (Pto S and S to P). Recently the BARS methodology has been applied to shear data from a dipole source. Much of the published work is in an open-hole environment. In our case study a BARS image was acquired in a layered carbonate reservoir in a horizontal well behind casing. The objective was to acquire a base image prior to a planned hydraulic fracturing job for comparison with the post-fracturing image. Both, monopole and dipole data were used to do the imaging. Data acquired shows that the BARS technique overcame uncertainties associated with; arrival of the casing modes, cement conditions, attenuation of the reflected signal at the casing/cement/formation interfaces and provided reliable results behind casing up to a distance of 100 ft away from the well.