Azimuthal AVO Analysis on High-density ISS®, OBC data, Trinidad & Tobago

In this study we analyse Amplitude Versus Offset (AVO) on different azimuth sectors from a high-density full-azimuth OBC dataset acquired in the Columbus Basin of Trinidad & Tobago. The OBC acquisition covers an area of approximately 1000 km2 of some of the most prolific acreage in the region where some of BP’s major gas fields are located. In some parts of the study area shallow gas is present, often concentrated in shallow stacked sands and creating imaging challenges. The azimuthal AVO analysis is performed on migrated Offset Vector Tiles (OVT) containing up to 1080 traces at each image point and covering azimuth ranges from 0 to 360 degrees and offset ranges from 180 m to 10 km. Reflections with travel paths passing through the shallow gas often lead to lower signal-to-noise OVTs and larger NRMSE values. Azimuth sectors containing such reflections provide a different AVO response than that predicted from well-logs and from observations of azimuth sectors where the data avoided the shallow gas. Here we characterize the variations in azimuthal AVO at different locations, analyse the major factors contributing to these variations, as well as suggest possible solutions for compensating or correcting for these AVO azimuthal variations.