Page 52: of Offshore Engineer Magazine (Sep/Oct 2013)

51 53

Geology & Geophysics

Figure 2. The initial velocity model is smooth and does not show geologic detail.

Figure 3. After FWI update, the velocity model shows high-resolution features and conforms to structures, with velocity contrast across faults. pre-stack depth migration (PSDM) Graham Conroy for their support with velocity model building work with stack response is also improved after the inversion engine. We appreciate the both ray-based tomography and full the inversion, see main image Map 1. input from Tony Huang, Kyle Huang, waveform inversion. Zhu holds a

Further, beam migrations show that Qiaofeng Wu, Yunfeng Li and Kristin B.Sc. in physics from the University of the gather fatness is mostly improved Johnston. Science and Technology of China and and the detailed velocities result in a Ph.D. in physics from the University more consistent curvature across the Authors of Houston. orthogonal azimuths. The improve- Sabaresan Mothi has worked for ment from the gathers is subtle because CGG for six years. Mothi earned an

FURTHER READING the starting velocity model had two MS degree in electrical engineering iterations of refection tomography. from Texas A&M University and a MS

These results clearly show the image degree in computational and applied Bi, H., and Mothi, S., 2012, improvement that additional offsets mathematics from Rice University. Application of FWI to Resolve Gas and azimuths bring to the inversion by Cloud Velocity Anomaly in Deep Water illuminating more subsurface angles Katherine Schwarz has worked for Gulf of Mexico. EAGE 74th EAGE and deeper sections. This approach CGG for four years. She is a senior seis- Conference, W014.

produces interpretive models that bet- mic imager with experience in TTI and ter characterize the different geological orthorhombic depth migration in the Tarantola, A., 1984, Inversion of sections. Gulf of Mexico and on land. Schwarz seismic refection data in the acous- earned a PhD in physics from the tic approximation. Geophysics, 49,

Acknowledgements University of California at Berkeley. 1259–1266.

The authors thank CGG for permission Huifeng Zhu has worked for CGG for to publish these results and acknowl- three years and is currently an imaging A complete list of references is avail- edge Yu Zhang, Andrew Ratcliffe, and project coordinator. He has performed able from the authors.

OE | September 2013 oedigital.com 54 052_OE0913_G&G1_CGG.indd 54 8/18/13 8:25 PM