Azimuth ambiguity elimination for borehole imaging using 3D borehole RIM scheme

A key technical challenge facing borehole acoustic reflection imaging is the uncertainty concerning the azimuth (Le. the direction about the axis of the borehole) from which a reflected event arrives. In generating images of formation boundaries near the borehole this is referred to as azimuthal ambiguity. The phenomenon is comparable to the 3D out-of-plane effects encountered in imaging of 2D surface data. Systems with multiple receivers (e.g., the sonic scanner tool developed by Schlumberger) acquire sufficient information to uniquely image reflected wave energy at its correct azimuth. However, a full use of this information requires the wave data to be analyzed in the context of 3D, two-way elastic wave propagation and a suitable anisotropic medium. Here we summarize the development of a 3D anisotropic reverse time migration imaging scheme to sonic data, and demonstrate that within this imaging formulation azimuthal ambiguity is resolved for data from both monopole and dipole sources. (C) 2019 Elsevier B.V. All rights reserved.