9C-2D seismic data analysis: Olds, Alberta

Grace Y. C. Yang, Robert R. Stewart

This paper discusses procedures to interpret nine-component, 2-D seismic data. These procedures are used to differentiate productive dolomite from non-productive limestone and estimate the trends of permeability.

P-wave and S-wave vibrators were used in this study over a 10.3 km line. Three-component receivers recorded each source orientation. The P-P wave data are excellent, the P-SV data is very good. SH-SH data are somewhat noisier. The other sections are marginal.

The analysis technique employed measures the traveltime, the amplitudes and the velocity ratio of the shear ( S) and compressional (P)-wave directly from stacked seismic sections. At each surface position along this seismic line, the ratio of the shear to compressional traveltime and Poisson's ratio near the target horizon are calculated and plotted as a function of shot points. There is a strong correlation between the observed lateral variation in the measured S and P wave travel time, their ratio, and Poisson's ratio with known facies changes in the geological cross section.

This study indicates that it is possible to separate the low permeability bedded facies from the high permeability stramotoporoid using the analysis of traveltime of a given interval among the various component seismic data. The plots of the P- and S- wave velocity, such as Vp/Vs ,Vs/Vsv or Vs/VsH versus shot points show that this seismic line can be separated into three different regions of various Vp/Vs values: The average Vp/Vs value of 1.73 on the east and average value of 1.65 on the west coincide with the higher permeability facies whereas the low average value of 1.50 in the middle corresponds to the low permeability bedded facies. The plots of Poisson's ratio also show similar separations. These results refines the geological model (base on cores) and improve our knowledge of the distribution of permeability and porosity trend in the area.