oa 3D General Surface Multiple Prediction on Full Azimuth Coil Shooting Survey

Offshore Kalimantan, Indonesia in the Tarakan Basin, seismic illumination has been a problem for interpreters for many years due to its complex geology. During the summer months of 2008 a full azimuth Coil Shooting survey of approximately 536 sqkm was conducted over the Tulip field. Unlike conventional race-track acquisition, in which the vessel traverses a straight line, with Coil Shooting the vessel traverses a circular pre-plot. This geometry fully sampled the full azimuth range to overcome a number of geological issues which resulted in very poor target imaging. With acquiring a true full azimuth survey benefits signal sampling it also acquires a multiple dataset fully sampled in azimuth. Due to the water-bottom shape and reflectivity complexity of the field, the resulting seismic data contained strong and complex surface-related multiples that conceal the underlying primary seismic energy. Due to the crossline rugosity of the water-bottom the downward Reflection Points (DRP) of the multiple travel paths are not in line with the source and receiver points creating 3D multiple effects. It is well known that the effect of azimuth errors on multiples is greater then on primary events. In theory, conventional 3D Surface Related Multiple Elimination (3D SRME) can provide an accurate solution to these types of multiples. However for Coil processing, conventional 3D SRME as typically implemented will not produce an accurate multiple prediction model. Without an effective de-multiple process, the resulting image from data processing can provide limited information. Recently WesternGeco introduced 3D General Surface Multiple Prediction (3D GSMP*) as a solution to attenuation of multiples in this type of environment. 3D GSMP is a practical approach to 3D SRME that can handle the irregularities in real life survey geometries and provide a superior multiple model prediction. It takes care of 3D effects and works in true azimuth. Without 3D GSMP, strong residual multiples obscure the seismic image of Tulip Coil data, making any kind of seismic interpretation extremely difficult. 3D GSMP produced a final image with minimal or no residual multiples. This paper will illustrate the successful use of this approach.