Simultaneous time imaging, velocity estimation, andmultiple suppression using local event slopes

摘要

Starting with the double-square-root equation we deriveexpressions for a velocity-independent prestack time migrationand for the associated migration velocity. We then usethat velocity to identify multiples and suppress them as partof the imaging step.To describe our algorithm,workflow, andproducts, we use the terms velocity-independent and oriented.While velocity-independent imaging does not require aninput migration velocity, it does require input p-values alsocalled local event slopes measured in both the shot and receiverdomains. There are many possible methods of calculatingthese required input p-values, perhaps the simplest is tocompute the ratio of instantaneous spatial frequency to instantaneoustemporal frequency. Using a synthetic data setrich in multiples, we test the oriented algorithm and generatemigrated prestack gathers, the oriented migration velocityfield, and stacked migrations.We use oriented migration velocitiesfor prestack multiple suppression.Without this multiplesuppression step, the velocity-independent migration isinferior to a conventional Kirchhoff migration because theoriented migration will flatten primaries and multiples alikein the common image domain.With this multiple suppressionstep, the velocity-independent are very similar to aKirchhoffmigration generated using the known migration velocity ofthis test data set.