Estimating impedance from PP and PS seismic data at the Ross Lake oilfield, Saskatchewan

Chuandong (Richard) Xu, Robert R. Stewart

A 3C-3D surface seismic data was acquired over Husky Energy Inc.'s Ross Lake heavy-oil field in southwestern Saskatchewan. In a previous interpretation, a Vp/Vs map between the Index Horizon Above Cantuar Marker (IHACM) and the RushLake horizon was calculated by combining PP and PS traveltime-thickness maps. In this paper, the impedance inversions are performed on the poststack PP and PS data using STRATA and ProMC. Dividing the average of the inverted P-impedance over an 8-ms horizon-based time window by the average of the inverted S-impedance over the same window, we map the Vp/Vs with higher vertical resolution. The Vp/Vs value derived from impedance inversion is generally lower than the Vp/Vs derived from the time-thickness ratios. The impedance Vp/Vs and traveltime Vp/Vs values show promising anomalies.