Joint PP-PS inversion at Pikes Peak oilfield, Saskatchewan

Hongbo Zhang and Gary F. Margrave

ABSTRACT

The method of simultaneous PP-PS inversion has recently been developed and tested on the 3D Blackfoot seismic data set. This paper shows the application of this method on 3C-2D seismic data from Pikes Peak oilfield. The inversion was accomplished with a newly installed inversion module in ProMAX. After careful prestack processing, five limited-offset stacked sections for each of the vertical and radial components were created, migrated, and correlated. The inversion module assumes that the data have been trace-equalized and, to restore the average AVO behaviour, it requires the input of scalar RMS amplitude estimates for each offset. These were obtained by creating elastic synthetic seismograms for P-P and P-S from well control and calculating the RMS amplitudes for each offset. Then the ten data sets, together with the RMS amplitude values and a background velocity model, were input into the joint PP-PS AVO inversion module in ProMAX. The weighted stacking requires estimation of the P-P and P-S incidence angles at each depth level and this is done by raytracing through the background velocity model. Four attributes were determined: fractional P-wave impedance ΔI/I , fractional S-wave impedance ΔJ/J , Δ(λρ)/λρ , and Δ(λ/μ) (λ/μ). Good correlation of these parameters from seismic inversion and those calculated from well logs shows that simultaneous PP-PS AVO inversion can be used to indicate anomalous lithology and pore-fluid changes in the subsurface. Therefore it should be helpful in detecting hydrocarbons using 2D multicomponent seismic data.

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