First Broadband, Full Azimuth Marine Seismic Survey in Malaysia: Deployment of Two Cutting Edge Acquisition Techniques

Abstract

Summary PETRONAS recently conducted the world’s first 3D broadband full azimuth marine seismic survey by an operator in East Malaysia. The survey seamlessly deployed two of the most cutting edge acquisition technologies concurrently i.e. the circular shooting technique for extending the azimuth sampling and the constant gradient slant cable towing technique to extend the bandwidth sampling. The legacy narrow azimuth 3D streamer data, acquired in the year 2001, suffers from poor imaging in the zone of interest. Though there were two successful wells with hydrocarbon discovery in the areas which have good seismic data quality, the area in between these wells is characterized by poor quality seismic data not amenable for interpretation and delineation of the reservoir. This poor data zone is understood to be caused by the inadequate illumination of the target horizon and low energy penetration through the monotonous shale in the overburden. Prior to the data acquisition, a survey design and modeling study was performed to select the optimum acquisition technique. A 3D earth model was created using the surface seismic and borehole data. 3D illumination ray tracing was performed at the target horizon using different acquisition geometries such as conventional narrow azimuth, multi azimuth and full azimuth circular shooting. A pilot broadband circular shooting survey was conducted over a subset of the study area based on the parameters derived from the survey design and modeling study. The time imaging processing result shows significant improvement in the seismic image at the target interval as well as the shallow level as compared to the legacy data. The extension of azimuth sampling and broader bandwidth enabled by the slant streamer circular shooting acquisition technique provides a superior image compared to the conventional narrow azimuth, flat streamer legacy data. These advanced acquisition techniques have the potential to offer solutions for other areas with similar imaging challenges in South-East Asia.