Optimal supra-salt model building in the central Gulf of Mexico using full-waveform inversion and multiparameter anisotropic tomography

摘要

Building an accurate supra-salt sediment velocity model is critical for salt interpretation, subsalt imaging and image-to-well tie. By combining well data and multiple-azimuth seismic data in a joint inversion, tilted transverse isotropy tomography is able to invert for Vp, epsilon, and delta simultaneously, improving gather flatness and well marker tie at the same time. However, reflection tomography is less effective in shale body areas where a lack of reflectivity is one of the main culprits. It also has some difficulty in areas where carbonate rafts are present, which have much higher velocity than surrounding sediments. Full-waveform inversion is able to use refracted waves and diving waves other than reflections; therefore, it can complement reflection tomography in the challenging areas where reflection tomography has difficulties to resolve. The combined work flow was successfully implemented on a large project in the central US Gulf of Mexico where the water depth varies from few hundred feet to several thousand feet, with the known presence of massive shale bodies and carbonate rafts.