Case History - A North Sea Low Gas Saturation DHI Failure

Presented here is a case history of a failed DFI prospect (Dunvegan) from the U.K. sector of the North Sea in which the presence of low gas saturation can be demonstrated using real-time gas readings, LWD and wireline log data as well as direct fluid sampling. In this case, prior to drilling the seismic data indicated class III and class II AVO behavior that when calibrated using nearby wells was thought to represent a sand saturated with gas overlying oil. The proposed oil leg (class II AVO) of the prospect was targeted but the well encountered only low saturation gas. No examples of low gas saturation had been encountered in any of the wells in the area previously and no risk of low gas saturation was applied during pre-drill risking.