Block 15/18a, operated by Petro-Canada, lies approximately 210 km north-east of Aberdeen (Figure 1) situated in the Outer Moray Firth. Recent technical work has focused on a complex Tertiary channel within which a prominent seismic anomaly exists. This channel system also contains the Macculloch and Brenda fields further to the southeast (Jones et al.) 2004). The channel system exhibits strong seismic reflection character due to significant contrasts in acoustic properties between the reservoirs (Forties and Balmoral sands) and the shale envelope (principally Sele Formation claystones). It is clear from the number of hydrocarbon bearing intervals penetrated by various wells along this Paleocene fairway, both within the channel and on its margins, that the channel system acts as a migration conduit for both oil and gas.

 

Consequently, within the fairway there exists both strong lithology related anomalies and direct hydrocarbon indicating anomalies (DHIs), some of which underpin key exploration targets in the licence. The high quality seismic attributes serve to reduce pre-drill technical risk and allow assignment of high probabilities of success for individual prospects. However, key commercial risk is assigned to accurately predicting the hydrocarbon phase with different development models affecting the perceived value for oil versus gas. This paper seeks to document an experience with elastic impedance inversion, which is aimed at distinguishing between the complex range of possible lithology and fluid effects.