Improved Sub-Salt Imaging by Leveraging Advanced Data Acquisition and Reverse-Time Migration

摘要

Reverse-time prestack depth migration (RTM) has over the last couple of decades been established as an accurate and robust depth-imaging tool. Continuous advances in CPU speed and computer technology are helping make RTM more cost efficient. Today, we see it being used as a standard tool in most seismic imaging projects in conjunction with other imaging tools such as one-way wavefield extrapolation migration and Kirchhoff migration. Reverse time migration uses the full two-way wave equation for the wavefield extrapolation steps; hence there is no intrinsic dip limitation with this approach. This allows the method to handle turning waves and multiply reflected prismatic waves. All migration methods benefit from spatially well-sampled input data with a large acquisition aperture. The introduction of wide-azimuth towed streamer (WATS) surveys has helped improve both aspects by offering wide receiver spreads and dense sampling. This ensures a more complete initial boundary condition for wavefield migration schemes, which again leads to improved sub-surface images. Applying RTM to wide azimuth data is a proper match between a state-of-the-art imaging algorithm and state-of-the-art acquisition. Here, we outline some of the challenges of implementing RTM so that it can be applied to exploration-scale datasets and wide-azimuth data in particular. We illustrate the performance of the RTM algorithm through comparisons with Kirchhoff, one-way wavefield migration and beam migration on a wide azimuth field dataset from the Gulf of Mexico.