3D common image gathers from Reverse time migration

Abstract

Wide azimuth acquisition (WAZ), together with reverse time migration (RTM), have greatly improved our capability to image the complex structures. To further take advantage of the advanced imaging techniques, we require RTM to output 3D common image gathers (CIGs) for different reflection angles and subsurface azimuth angles. In this paper, we introduce a straightforward method for computing 3D CIGs using the wavefields generated in RTM. We derive the RTM imaging condition for 3D CIGs based on true amplitude migration theory. The method adapts to both isotropic and VTI/TTI anisotropic migrations. The 3D CIGs retain the rich azimuth and reflection angle information carried in WAZ data. They can be used to build velocity models, invert anisotropy parameters and to analyze reservoir attributes. In the numerical section, we demonstrate our method using high resolution 3D CIGs on a synthetic dataset as well as on a WAZ dataset in the Gulf of Mexico.