Zhao, Yang (Aramco Services Company: Aramco Research Center-Houston) | Zhang, Houzhu (Aramco Services Company: Aramco Research Center-Houston) | Liu, Hongwei (EXPEC Advanced Research Center, Saudi Aramco)
Interferometric virtual source (VS) redatuming crosscorrelates downgoing waves with the corresponding upgoing waves to convert records from surface-source gathers to virtual gathers at the buried receiver locations. It can be viewed as cancellation of common parts of raypaths from surface sources to different buried receivers. A stacking operator, a uniform or simple offset function, is then applied to weight and sum the surface-source array to form the VS. The assumption is that the stacking operator should preserve sources associated with effective cancellations of overlapping raypaths, and suppress ineffective-cancellation sources. However, intricate shallow structure and highly variable weathering layers can severely distort the raypaths in the presence of complex near surface. As a result, sources associated with ineffective-raypath cancellation can produce substantial artifacts, instead of being spatially suppressed by the conventional stacking operator. To address these issues, we propose a data-driven VS method with a diversity stacking theme, where individual source contribution is weighted by certain quality measures. Specifically, we predict the upgoing wavefields using the conventional VS response, and use the quality of these predictions compared with the original upgoing wavefields to approximate the weight of each source for the diversity stacking. Compared with previous methods, the new VS approach provides improved image quality and repeatability based on a pilot field of 13 time-lapse surveys, which reduced a significant repeatability problem across a 17 month survey gap.
Presentation Date: Wednesday, October 17, 2018
Start Time: 1:50:00 PM
Location: Poster Station 6
Presentation Type: Poster