The first deepwater well in Norway and its implications for the Upper Cretaceous Play, Vøring Basin

Abstract

Well 6707/10-1 in the Nyk High licence PL218 was the first exploration well to be drilled in the deepwater Vøring Basin. It targetted a prominent tilted fault block trap with a pronounced flatspot conforming to structure. The pre-drill evaluation highlighted gas-over-water, with the gas–water contact (GWC) at the flatspot, as the most likely case. Given the water depth of 1274 m and the remote location of PL218 this case was not commercially attractive. However, seismic attributes indicated the possibility of an oil leg below the flatspot and this gave the necessary encouragement for drilling the well. The presence of an oil-prone source rock, and more importantly, its maturation relative to trap formation, were seen as the main pre-drill risks. The well found an excellent quality Santonian to Early Campanian age reservoir of more than 1000 m thickness and a 156 m thick column of dry thermogenic gas. Poor oil shows were recorded on core chips and small amounts of heavier hydrocarbons were extracted from the core. This is seen as an important finding of the well, although the concern over the timing of maturation and migration relative to trap formation still remains. Reservoir presence is considered low risk for future wells in areas where the distinct seismic character can be tied to the Nyk High well. The sandy nature of the Santonian to Lower Campanian section does, however, also mean that traps relying on fault seal (e.g. hanging wall traps) are high risk and that the possibility for stacked pools is reduced compared to the pre-drill view. The flatspot does not match the current free-water level and is interpreted to represent an earlier, deeper gas–water contact. The reason why the contact moved up is not yet fully understood and may be a result of either late fault reactivations or gas compression during the Plio-Pleistocene burial. Late fault movement is a general concern in the Vøring Basin, with faults in some areas cutting up to seabed. If the contact moved up because of gas compression, it has the implication that gas charge to the trap, and Nyk High area, had ceased in the Plio-Pleistocene.