V P /V S from prestack multicomponent seismic data and automatic PS to PP time mapping

Osareni C. Ogiesoba and Robert R. Stewart

ABSTRACT

This paper discusses the development and application of a prestack method that scans for the average vertical velocity ratio (V P /V S ) value, generally referred to as γ 0 , and the stacking velocities of multicomponent seismic data using a converted-wave (PS) nonhyperbolic traveltime equation. The procedure entails computing semblance as a function of two variables namely, the PS stacking velocity V PS , and γ 0 , with respect to the PS zero-offset time t ps0 . The results are displayed in 2D plots. We tested the procedure using numerical data sets and real data sets from the Blackfoot Field in Southern Alberta. We observed that the γ 0 values from the scanning method agree reasonably well with the γ 0 values from the well log of Well 09-08 located at the CDP location at which the analysis was performed. In addition, when these γ 0 estimates are used for PS-PP time mapping, the time difference between the computed and actual PP time at the target level is found to be 10 ms; being an error of less than 3%.

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