Multi Azimuth Survey Design for a Complex Carbonate Reservoir in Offshore Spain

Wide azimuth seismic surveys are needed in areas where conventional narrow azimuth streamer seismic data is insufficient for cost effective field development. Wide azimuth surveys are required in areas with illumination challenges or/and critical anisotropy or/and fracturing systems. Carbonate reservoirs may have a rapid spatial variation of their rock properties and lateral structural heterogeneities. They are difficult to characterize and have associated a high risk in structural interpretation. Objective of seismic data acquisition is not only to reduce the uncertainty of the final structural model but as well to determine the properties of the complex carbonate reservoir such as fracturing systems and their spatial distribution. Ray Tracing Modeling showed that there were not illumination issues. Anisotropy with associated velocity field changes on direction will cause small changes in the travel times to horizons. If the anisotropic effects are not considered, structural image may be degraded or there will be uncertainty in the position of the structural evens. However, the changes in travel times only will produce small variations in total illumination.