Understanding refracted wave paths for Brazilian pre-salt target-oriented imaging

Abstract

Refracted seismic waves recorded on Ocean Bottom Nodes (OBN) from all azimuths benefit from high Signal-to-Noise Ratio (SNR) and may provide important information about deepwater reservoirs, especially those below massive salt bodies. For target-oriented imaging, refracted wave paths can help understand accurately how the geometry of acquisition illuminates the target region, thereby supporting cost-effective survey designs. To this end, we study two techniques: (i) wave paths calculated by a Reverse Time Migration (RTM) algorithm for refracted wave events selected in synthetic seismograms; (ii) ray tracing using the eikonal equation. We discuss illumination examples for two models: a 3D velocity model typical of the Brazilian pre-salt fields and a simplified multilayered 2D approximation. We show that wave paths can map a given source-receiver pair into illuminated regions for selected refracted first arrivals. For the pre-salt refractions we can establish an offset range for successful reservoir imaging. Presentation Date: Wednesday, October 14, 2020 Session Start Time: 9:20 AM Presentation Time: 11:00 AM Location: Poster Station 8 Presentation Type: Poster