Accurate salt geometry is critical for imaging subsalt structures, but obtaining an accurate geometry is challenging in narrow mini-basins with surrounding salt bodies.
Wavefields undergo strong distortion when they propagate through the top of salt and become more complex due to multiple bounces at the sediment/salt interfaces.
Although RTM is the natural way to image the prismatic (i.e. double-bounce) waves, conventional top-down approaches to imaging the salt surfaces around narrow mini-basin areas are inadequate.
The CGG salt delineation workflow, called Dual Flood RTM, takes advantage of prismatic waves to image salt flanks around narrow mini-basins. The result is an accurate salt geometry and clarity in the subsalt region.
By simultaneous utilisation of two velocity models (sediment and salt), Dual Flood RTM can decrease the total number of iterations needed for overhang imaging.
Data from the Walker Ridge area of the Gulf of Mexico, imaged using sediment flood RTM (top) and Dual Flood RTM (bottom). The Dual Flood better defines the top of salt. The yellow lines indicate a prismatic wave ray path.
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