Various strategies for populating the shallow portion of the prestack depth migration (PSDM) velocity model are explored in a carefully-controlled synthetic environment which mimics a real-world Permian Basin unconventional play. Key findings from the synthetic experiments are corroborated by analogous observations on real data, suggesting that the experiments are capturing realistic effects. These synthetic experiments clearly demonstrate that gather flattening improves dramatically with application of the more sophisticated shallow model building approaches. In the case of the most primitive approaches (e.g., migration-from-flat-datum or migration from topography while populating the shallow model with a spatially homogenous "replacement" velocity), the migrated gathers exhibit significant residual moveout, and applying a tomographic velocity update to improve flattening leads to a significant error in event depth location (i.e., "depthing"), a finding that in turn suggests that downstream anisotropic parameter estimation will be compromised unless a more sophisticated shallow model building approach is employed. The concept of differential statics is introduced and is demonstrated to be a useful tool which can provide good gather flattening, accurate event depthing, and also improved lateral continuity of events in the common case where the near-surface velocity estimate from refraction statics analysis is not suitable for verbatim insertion into the shallow PSDM model.
Presentation Date: Tuesday, September 17, 2019
Session Start Time: 1:50 PM
Presentation Start Time: 3:55 PM
Location: 303B
Presentation Type: Oral
