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Reflection-refraction Tomography and Complex Salt Structure - A Case Study from Offshore North GabonNormal access

Authors: J. Chaloner, P. Esestime, B. Cox, H. Nicholls and L. Letki
Event name: Second EAGE/PESGB Workshop on Velocities
Session: High Contrast Media
Publication date: 04 April 2019
DOI: 10.3997/2214-4609.201900052
Organisations: EAGE
Language: English
Info: Extended abstract, PDF ( 6.57Mb )
Price: € 20

elocity model building in basins with complex salt structure typically relies on a heavily interpretation-driven process. An industry-standard workflow would involve several rounds of top salt and base salt horizon interpretation, combined with several migrations to test the scenarios using different flood velocities. For very large surveys in areas with extensive salt bodies, the time and expense required for such an involved workflow can be prohibitive, particularly in the early stages of exploration. We show that an alternative approach relying on the careful application of refraction and reflection high resolution tomography can be used to resolve sufficient details in the velocity model to characterise the salt structure, allowing a more accurate interpretation with a reduced number of interpretation phases. This is illustrated using examples from offshore North Gabon, where the use of a data-driven approach to derive the starting point for an initial one-pass manual interpretation of the salt bodies was key to enabling the rapid turnaround of the model building. A traditional approach with multiple interpretation passes would have been impractical in the available time-frame, given the large area (approximately 5500 sq km) and multiple complex salt bodies.

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