_ This article, written by JPT Technology Editor Chris Carpenter, contains highlights of paper IPTC 24791, “Beyond RTM: Rapid High-Frequency Wave Imaging Gathers Output up to Nyquist Frequency To Improve Imaging and Resolution of Complex Geology—A Case Study of Examples From OBC and Marine Data Sets, ” by Elia Gubbala and Jagat Deo, Seismic Image Processing, and Chris Kent, PGNiG, et al. The paper has not been peer-reviewed. Copyright 2025 International Petroleum Technology Conference. _ This paper describes the implementation of one-way wave equation in slowness domain outputting gathers up to Nyquist frequency, which can be used to generate high-resolution seismic sections; the gathers can be used for amplitude-vs. -offset (AVO) studies. The implications of the methodology are presented with example data sets such as marine, ocean-bottom cable (OBC), and land 3D seismic. Introduction Reverse time migration (RTM) has long been used for solving complex imaging when ray-based methods fail because of complexity in subsurface imaging. RTM has delivered major success during the past few decades but has limitations. The model input to RTM, because of the two-way full elastic method, must be highly precise. RTM computing times also increase quadrature with frequency. In this paper, the authors aim to present the best way to implement the extended guided-wave one-way wave equation to produce image gathers up to Nyquist frequency, which can be used for high-resolution enhancements and AVO. Method The guided-wave-equation imaging used here is an implementation of the shot-based one-way wave-equation method in pseudoacoustic approximation using the phase shift plus interpolation scheme. It supports isotropic and anisotropic subsurface models and allows migration of the input shot gather data and output, both gathers and the stack. The input shot data is split into receiver patches around a central offset (and azimuth), and migration is executed. Each partial result is stored and sorted into its corresponding offset class. This method has by far the least implementation risk and provides surface-offset and surface-azimuth gathers. A depth variable (local) step size (dz) is introduced by linking the maximally allowed input-data time sampling consistent with the Nyquist sampling theorem with a reasonable bulk velocity at the current depth level. A reasonable bulk velocity could be the average or the minimal velocity at a given layer. In this way, in regions where the velocity is slow, the dz is small enough to sample the data correctly, but, for regions where the velocity is higher (under an unconformity), the dz is larger, with no compromise. To provide support for tilted-transverse-isotropy (TTI) media, a method described in the literature for a constant TTI medium in a single depth step has been adapted. The TTI kinematics for nonconstant, spatially varying models are designed to keep modest run times. This imaging code supports offset gathers, topography for land seismic, and TTI models while preserving aspects of high-performance computing to further enhance image quality compared with other ray-based and wave-based depth migrations.
Chris Carpenter (Sun,) studied this question.