Mapping Bedrock Topography With Seismic Refraction At An Oil And Gas Field: A Comparison Of Engineering And Petroleum Exploration Methods At A Site In The Wind River Basin Of Wyoming.

“Weathered-layer” corrections to seismic-reflection travel times for deep hydrocarbon exploration are often made<br>using shallow refracted arrivals on the reflection records. There has been recent interest in using these “refractionstatics”<br>solutions to provide depth-to-bedrock maps for environmental or engineering applications as a by-product of<br>the deep seismic survey. We show that the depth to bedrock and bedrock velocities produced by automatic<br>refraction-statics processing of a three-dimensional seismic survey of a gas field in Wyoming differ significantly<br>from those determined from an engineering survey. Manual reprocessing of the refraction statics produced some<br>improvement, but is still inferior to refraction data taken for the specific purpose of determining depth to bedrock.<br>Automatic refraction statics provide adequate travel-time adjustments to reflection records due to a shallow lowvelocity<br>layer, but such solutions should not be taken to represent explicit depth to bedrock.