VSP interpretation from Joffre, Alberta

Qi Zhang, Zandong Sun, R. James Brown, Robert R. Stewart

The Joffre 3C-3D seismic survey was conducted to try to differentiate a dolomitized vuggy porosity Nisku reservoir from regions plugged by a later-stage anhydrite. Conventional P-wave images had not been successful. A suite of VSP data (near-offset, offset, and walkaway) including P-P and P-SV data has been processed. Compared with surface 3D P-SV seismic data of good quality, P-SV VSP data provide much higher resolution and better images of all horizons. It is evident that the lateral variation of the Nisku dolomite reservoir due to the anhydrite seal can be seen on the P-SV VSP map, and that this is not clear on surface 3-D P-P, P-SV (converted-wave) images, nor on the VSP P-P image.