Depth-Domain Pre-Stack 4D Seismic Inversion in Complex Geology
C. Gerea, J. Beckwith, E. Bergounioux, C. Rivera and C. Agut
Event name: 81st EAGE Conference and Exhibition 2019
Session: Time-Lapse Processing
Publication date: 03 June 2019
Info: Extended abstract, PDF ( 840.48Kb )
Price: € 20
Present industry 4D workflows normally use the co-processing and imaging of baseline and monitor surveys with the same depth-interval velocity model. Standard practice is to re-align the migrated offset or angle stacks vintages with dynamic 1-D Warping and extract amplitude differences for 4D interpretation. A weakness is that in complex geology dominated by laterally-variant anisotropic overburden and steep-dipping reservoirs in proximity of salt or sub-salt, the production-related 4D changes are not accurately described and compensated for during the generation of post-stack 4D attributes. The relationship between dynamic warping time-shifts and velocity changes relies on a 1D assumption of wave propagation. This leads to major uncertainty and errors in magnitude, shape and spatial location of inverted 4D velocity perturbations that could severely affect the interpretation. We challenge this prevailing dogma, and motivated to integrate rigorous physics we investigate 4D velocity-change inversions in pre-stack domain where the production-related time-shifts and amplitude effects should better differentiate towards robust assessment of overburden structural deformation and pressure/saturation reservoir changes. We demonstrate it with realistic 3D elastic synthetic and field data examples, and emphasize the importance of tailored 4D processing and inversion workflows to mitigate risk and improve reservoir management decisions.