Vector-acoustic reverse time migration of Volve ocean-bottom cable data set without up/down decomposed wavefields

Abstract

Methods for wavefield injection are commonly used to extrapolate seismic data in reverse time migration (RTM). Injecting a single component of the acoustic field, for example, pressure, leads to ambiguity in the direction of propagation. Each recorded wavefront is propagated both upward and downward, and spurious (or ghost) reflectors are created alongside real reflectors in the subsurface image. Thus, wavefield separation based on the combination of pressure and particle velocity data is generally performed prior to imaging to extract only the upgoing field from multicomponent seabed or towed marine seismic recordings. By instead combining vector-acoustic (VA) data with monopole- and dipole-type propagators in the extrapolation of shot or receiver gathers, we show that wavefield separation (or deghosting) can instead be performed “on-the-fly” at limited additional cost. This strategy was successfully applied to a line of a North Sea ocean-bottom cable data set, acquired over the Volve field. We then evaluate additional advantages over standard RTM with decomposed fields such as improved handling of the directivity information contained in the acquired VA data for clearer shallow sections and better focused space-lag common image gathers, and imaging of the downgoing component without the need for additional finite-difference modeling via mirror migration. Finally, we prove the robustness of our method with respect to sparse and irregular receiver sampling.