CGGVeritas: Continuous Innovation in Subsalt Imaging (USA)
“If I have seen further it is by standing on the shoulders of giants”, attributed to Sir Isaac Newton, refers to the development of scientific research and understanding. This sentiment is equally applicable to the technology-driven seismic industry, and the discipline of subsalt imaging in particular. The latest imaging technologies build on a rich heritage of pioneering technology with CGGVeritas consistently at the forefront.
The Gulf of Mexico, with its rich hydrocarbon rewards and complex geological structures, has been a traditional testing ground for seismic imaging techniques. It has witnessed an astonishingly rapid evolution in migration algorithms, velocity model building techniques and marine acquisition methods.
Depth migration technology has evolved from the post-stack depth migration used in the late 1990s through to the latest Reverse Time Migration (RTM) techniques. The clarity of RTM is now available prestack in the form of RTM 3D gathers, which retain the rich azimuth and reflection angle information inherent in wide-azimuth data, giving improved modeling results through better tomography, anisotropy inversion and true-amplitude reservoir attribute analysis.
No less vital to the final images are the velocity model building tools and methods. High-density and multi-layer tomography, along with Full Waveform Inversion (FWI), are currently state-of-the-art. Initially, both velocity model building and migration were isotropic only, but they now incorporate greater complexities of anisotropy to more accurately represent the real geological properties.
Historically, the internal structure of salt bodies has been ignored, which can compromise the base salt and subsalt imaging. In areas with suitable geology, such as Santos Basin, reflection tomography updates can now be made to salt velocities. Where tomography is not an option, if picks from intra-salt reflections are too sparse or erratic, “dirty salt” iterative reflectivity inversion can be used for modeling salt heterogeneities.
Likewise, variations in the near-surface would often be ignored. Spatial anomalies can cause amplitude shadow zones and wavelet distortion in deeper events. The introduction of Q tomography allows the modeling of these effects, with Q-enabled migration able to compensate and output data with the correct phase, amplitude and resolution. The latest velocity modeling techniques, such as FWI, derive increasingly detailed velocity models of the near surface, which provide stunning benefits when studying deeper targets.
Let us not forget the impact of acquisition on our ability to derive clearer images. CGGVeritas began the advance into wide-azimuth marine acquisition in 2004 with a survey for BP over their Mad Dog field. Subsequent wide-azimuth, multi-azimuth, full-azimuth and similar multi-vessel strategies provide better sampling of the seismic wavefield, to derive ever more accurate understanding of reservoirs. StagSeis is our next-generation full-azimuth solution, taking the concept of wide-azimuth marine acquisition to the next level.
Driven by the development of wide-azimuth acquisition, true-3D, anisotropic tools and algorithms were designed to realize the full potential of that wide-azimuth date. They utilize all of the additional azimuthal information to provide improved noise and multiple suppression, azimuth-dependent velocities for flatter gathers and multi-dimensional interpolation and regularization.
Commitment to R&D
Research and development is vital to CGGVeritas and the quality and range of services we offer our clients. We invest 5% of overall revenue back into R&D which equates to a global annual budget in the region of $150m. In addition to our own research and development teams, we also participate in many industry partnerships and support academic consortia around the world.
Yu Zhang, Deputy Global Research Manager with CGGVeritas, was this year awarded the SEG Virgil Kauffman Gold Medal for his contribution to RTM subsalt imaging. According to the Medal citation, “Yu exemplifies for all of us an outstanding drive and ability to apply powerful and innovative mathematics to the real-world complications of actual seismic data”. This is clear recognition of the value of cutting-edge research that has kept CGGVeritas at the forefront of the seismic industry.
The flurry of advances in seismic imaging continues unabated throughout 2012. Much of CGGVeritas’ ongoing research is being presented in the SEG technical sessions where Yu Zhang is presenting one of his latest projects, “compensating for source and receiver ghost effects in reverse time migration”. Other papers demonstrating our capacity for innovation discuss tilted orthorhombic imaging, FWI, multi-layer tomography and the use of RTM in multiple prediction.
Press Release, November 08, 2012