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The AAPG/Datapages Combined Publications Database

Wyoming Geological Association


Resources of Southwestern Wyoming; Field Conference Guidebook, 1995
Pages 77-88

Three-Dimensional Depth Imaging of Seismic Data, with Examples from the Overthrust Belt of Southwestern Wyoming

Alvin K. Benson


Seismic data from the Overthrust Belt of southwestern Wyoming should typically be depth imaged in Previous Hit3-DNext Hit. A simplified thrust model is studied to illustrate (a) the complications produced by rapid lateral velocity changes, velocity pull-up, etc., and (b) the necessity of using a depth imaging process versus time imaging plus conversion to depth in complex geological areas. Two case studies from southwestern Wyoming are examined todemonstrate new methods that provide improved images of seismic data. For both cases, stacking velocities were initially used to derive interval velocities for modeling, but this led to incorrect, contradictory geology. Subsequently, velocity information from available well logs helped produce much-improved depth models for the depth imaging process. When a grid of data is available, the imaging is typically done in Previous Hit3-DNext Hit.

In the second case study, a 2-D depth-imaged section leaves unexplained, crossing events due to seismic energy coming from out-of-the-plane. Subsequently, a two-pass, Previous Hit3-DNext Hit depth image was produced, which provides the "best" depth image, and the final interpretation, as confirmed by drilling, is much closer to reality. The objective of depth imaging, and when the data are available, Previous Hit3-DTop depth imaging, is to produce as accurate a picture of the actual geology of the earth as possible in areas of complicated geological structures.

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