Combining deblending with multi-level source deghosting
A. J. C. Stijn Berkhout, Gerrit Blacquière · 2014
A marine source that generates both a direct signal and a ghost signal - caused by the strong surface reflectivity - represents a blended source array. The two unblended source wavefields involved in this blending process correspond to the source at the actual location below the water level and to the corresponding ghost source at the mirrored location above the water level, the blending codes being +1 and −1 respectively. As a consequence, deghosting becomes deblending (echo deblending) and it can be carried out with a deblending algorithm. In this paper we present an iterative deblending algorithm that properly includes the angle-dependence of the ghost: it is a full wavefield solution. The output of the echo-deblending algorithm consists of two ghost-free shot records: one with the source at the actual location below the water level and one with the ghost source at the mirrored location above the water level. Optionally, the solution with a virtual source location at the water level is obtained as well. With our multi-level DSA (distributed source array) concept, where the wavefield is generated by a blend of narrow-band sources at different depths, notch-free seismic data is acquired. However, the ghost still causes attenuation at the high angles. The echo-deblending algorithm mitigates this effect while at the same time it produces a full-bandwidth result at the water level.