Before Maersk acquired the 12/30-1 licence (P2277) in 2015, the area was explored by Echo Exploration in a joint venture with Premier Oil. The relinquishment report of their P1920 licence provides a good summary of the so-called Badger prospect that was identified as the main target in the licence. It is assumed here that the Finzean prospect currently being drilled is the same as the previously mapped Badger structure, although this has not been confirmed by the operator.
The Badger prospect was thought to hold around 38 MMbbl of P50 recoverable oil, with an upside of (P10) 104 MMbbl.
The prospect is located in the Inner Moray Firth, which is part of the Upper Jurassic rift system. The area is part of the ESE-WNW trending Smith Bank half graben structure that dips to the north. The Smith Bank Graben, which in itself is dissected by numerous faults, is bounded to the south by an intra-basinal high called the West Bank High or Buckie Ridge.
The Badger prospect that was mapped by Echo Exploration is at the southern and updip margin of the Smith Bank Graben. The main reservoir is thought to be the Lower Cretaceous Hauterivian-Barremian deep-water channelised Coracle sandstone, but the slightly older Punt sandstone may be a target too.
Just north of 12/30-2, well 12/30-1 was drilled in 1974 as a stratigraphic test of the Mesozoic succession in the area. Very minor hydrocarbon indications were encountered in Lower Cretaceous and Permian sands in this well, which was abandoned as dry.
Trapping
The Badger prospect relies on a combination of structural and stratigraphical trapping. To the east and north, structural dip and downthrown fault closure respectively can be considered fairly robust. However, in the south, up-thrown fault closure is required against the Buckie Ridge, and stratigraphic trapping is the only way to make the prospect work in a western direction. The stratigraphic trapping was already regarded as the biggest exploration risk by Echo Exploration.
However, based on unexpected success in fields such as Buzzard, which also exhibits a stratigraphic trap configuration, this prospect should definitely not be discarded.
One more aspect related to this prospect that may be fairly important is charge. The Kimmeridge Clay is mature to the south of the Ross fault, but hydrocarbon migration may preferentially have taken place through the sands on the Buckie Ridge rather than the Smith Bank Basin in the north. This would leave the prospect in a migration shadow.
HENK KOMBRINK
