--> --> Abstract: In-Situ Shear-Wave Velocity Measurements and Their Impact on Amplitude-vs.-Offset Modeling, Sacramento Basin, California, by W. Tolmachoff; #90992 (1993).

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TOLMACHOFF, WAYNE, Dekalb Energy, Bakersfield, CA

ABSTRACT: In-Situ Shear-Wave Velocity Measurements and Their Impact on Amplitude-vs.-Offset Modeling, Sacramento Basin, California

With the arrival of amplitude-vs.-offset modeling programs, this information can be used as a quantitative predictor of

hydrocarbons. To reduce the number of assumptions made by these programs, it is important to have the relationship between shear-wave and compressional-wave velocities defined. Although there are measured laboratory velocities for rocks and limited in-situ measurements in wells, extrapolation of this information to a specific project may not be accurate enough to yield the desired modeling results. To solve this problem, a consortium of seven energy companies used Schlumberger's DSI tool to measure shear-wave velocities in a Sacramento basin gas well. The cross-plot of Vs vs. Vp for these measurements shows a significant difference from previously defined relationships. The impact of this difference is that Poisson's ratio does not vary as much as earlier thought for this area. The rezulting models show gradual changes in amplitude with offset.

AAPG Search and Discovery Article #90992©1993 AAPG Pacific Section Meeting, Long Beach, California, May 5-7, 1993.