An example of the improvement in source positioning brought about by DSC.
Working Towards Holistic 4D Workflows
DSC - Dynamic Spread Control enables the planning and automated positioning of the vessel, source, and cables for marine seismic acquisition, as well as quality control and quality assurance of the acquisition deliverables. The latest Q-Marine vessel, Western Spirit, is the first vessel to be equipped with the system and a large integrated oil and gas company will utilize DSC this summer (2007) in the North Sea.
REPEAT is the front-end 4D navigation planning module. The navigation plan created by REPEAT is input to the 4D Position Controller, which is at the heart of DSC. The controller dynamically steers the vessel, sources, and cables to match the 4D navigation plan. Post-acquisition results are then fed back to REPEAT for evaluation and verification. A recent E&P article Retracing Our Steps gives an in-depth illustration of this innovative approach.
DSC was tested in the spring of 2007 during a four-vessel, wide-azimuth survey in the Gulf of Mexico. The results showed that with just automated vessel steering it is possible to achieve less than 8 meters of crossline difference between the planned and actual source positions. Utilizing DSC resulted in less than 4 meters of crossline difference.
DSC is part of the process of handling the 4D workflow in a more holistic manner; DSC, together with enhanced 4D processing such as non-rigid matching and 4D inversion through Schlumberger 4D ISIS simultaneous inversion, clearly provides the tools for superior marine 4D survey planning and execution.
While improving the accuracy and effectiveness of 4D surveys is the primary application of
DSC, the technology can also be used to further improve the quality other Q enabled techniques
such as over/under and rich- and wide-azimuth surveys, as well as improving coverage and
reducing infill in 'regular' surveys because the same components and principles can be applied on a 3D survey.
