Multicomponent OBC (4C) imaging over Pamberi, offshore Trinidad

Abstract

Results from the P-P and P-Sv prestack time migration of a 2.5D four-component (4C) OBC seismic swath test acquired in 2004 over the Pamberi area in Block Lower Reverse L offshore Trinidad, are presented. The 4C swath acquisition consisted of twelve 100-m spaced source lines, shot into two parallel 15-km OBC receiver lines, separated by 400 m. A description of the processing applied to the recorded multicomponent (4C) seismic data, through curved-ray anisotropic Kirchhoff prestack time migration for both the compressional P-wave and mode-converted PSv-wave, is provided. Mode-converted shear-wave data acquired from 4C surveys allow for imaging where conventional seismic data are perturbed due to the presence of shallow gas and/or fluid in the pore spaces of the rock. Furthermore, mode-converted shear waves propagate with a different raypath than that of the compressional wave, thereby providing an alternative illumination of the subsurface target. As both the compressional P-wave and mode-converted S-wave record independent measurements of the same subsurface, more reliable rock properties can be uniquely determined, allowing for improved reservoir characterization and lithology prediction. A conventional streamer 3D survey was acquired over the Pamberi area in 2003, but failed to image or resolve adequately the target reflectors comprising the reservoir under the main growth fault. Therefore, the purpose of the 4C swath test was to evaluate the potential of long-offset multicomponent technology for resolving stratigraphic interpretation in complex areas with challenging geology. The processed images from both the compressional wave and mode converted shear waves are shown to illustrate the improvement in resolution at the reservoir prospect level which were not clearly evident on the previous conventional towed streamer 3D data volume.