First Break - Volume 42, Issue 5, 2024

Multi-component data recorded during Ocean-Bottom Seismic (OBS) surveys captures both PP and PS events. PP and PS images provide complementary information about reservoir properties. The quality of both these types of images depends on the accuracy of the P-wave and S-wave velocity models, VP and VS, respectively. In this paper, focusing on data from a shallow water OBS survey in the Central North Sea, we show, first, how a high-resolution 65 Hz VP model, obtained using Time-Lag FWI, can improve the imaging from the shallow to the deep. Similar improvements are then shown for PS data using a 30 Hz VS model obtained from PS reflection-FWI. The most remarkable achievement is the flattening of the undulating chalk and top reservoir surfaces on both the VP and VS FWI Images, obtained from PP and PS data, respectively, which was confirmed by drilling observations. These derived VP and VS FWI Images reduce the uncertainty in reservoir characterisation.

The Bay of Bengal contains the world’s largest deep marine fan and yet remains almost entirely unexplored for petroleum. Evaluation of more than 12,600 line km of 2D seismic, gravity and magnetics data acquired by TGS and their partners SLB in 2023 (Figure 1), alongside historic well data, has provided a regional framework for understanding the evolution of the whole geological history of the basin and insight into the extensive petroleum potential of this highly frontier region. In this paper, we will present high-resolution seismic imaging, characterising the facies and reservoir architecture within the fan and illustrating the extensive petroleum potential of the Bengal Fan, from shelf and slope to the deep water domain.