All migration methods, including Reverse Time Migration (RTM), need a way to preserve prestack information for reflection tomography and performing quality control for velocity model building, improving structural imaging via illumination weighting, post-migration reprocessing (PMR) and estimation of rock properties via AVA. There are several methods to preserve prestack information in RTM and the creation of angle gathers is the most common. Local plane-wave decomposition methods are considered the most reliable and accurate but are more expensive than other methods. The cost of creating high quality angle gathers means that it is not done frequently enough. Here we propose an efficient method to output sparse angle gathers from RTM based on plane-wave decomposition. The sparse angle gathers have several (six to ten) reflection angle bins with each bin about 5° to 15° wide. We ensure computational efficiency by outputting sparse angle bins and by avoiding wavenumber-domain convolution. The method first decomposes source and receiver wavefields based on propagation directions, and then cross-correlates the decomposed wavefields. The more finely we decompose the wavefields, the higher the computational cost. With sparse angle gathers, some applications may be restricted, such as velocity model updating. However, some other applications become more practical, such as velocity model QC and selective stacking, which are demonstrated here with synthetic and real data examples.
Presentation Date: Tuesday, October 13, 2020
Session Start Time: 1:50 PM
Presentation Time: 3:30 PM
Location: Poster Station 2
Presentation Type: Poster