Angle-domain common-image gathers in generalized coordinates

Angle-domain common-image gathers in generalized coordinates

Jeff Shragge

Abstract:

The theory of angle-domain common-image gathers (ADCIGs) is extended to migrations performed in generalized coordinate systems and subsurface offset axes generated by nonlinear wavefield shifts. I develop an expression linking the definition of reflection opening angle to various geometric and nonlinear shifting factors. I demonstrate that, under certain circumstances, generalized coordinate ADCIGs can be calculated directly using Fourier-based offset-to-angle approaches. Cartesian and elliptic coordinate examples are given to validate the theory. A method for eliminating geometric factors from the ADCIG expression using judicious wavefield shifts is derived; however, this approach is not likely computationally advantageous in practice.