Badger23 Aug 2018 12:26
giving dip closure. To the north it is bounded by an east to west downthrown fault that bisects the Coracle channel. Smaller faults can be seen cutting the channel in 13/26. In the south, the sand fairway appears to be limited by an up-thrown W-E fault that bounds the main West Bank High. The channel system continues to the west and north such that the channel margin forms the stratigraphic trapping limit just to the west of the block boundary. The crest of the structure is at 3,400 ft tvdss and the hydrocarbon column is limited by the WUT of -4,372fttvdss in 12/30-1 giving an area of ca. 6,500 acres in the Coracle Sandstone.
Reservoir: Lower Cretaceous sandstone has been encountered in four key wells: 12/30-1, 13/26b-3, 13/27-2 and 13/28-8 where significant net sand is present. Of these 12/30-1 and 13/28-8 have identified a Coracle aged channel sand system. In all cases the reservoir is of high quality with porosities from 25% to 30% and the net Coracle sand in 12/30-1 is 78 feet. The Punt sand is more widely spread and is 300 feet thick and more in these key wells. Permeability in both reservoirs is typically hundreds of millidarcies to darcies.
Seal: The top seal for the Lower Cretaceous Sandstones are the thick mudstones of the overlying Valhall Formation. Laterally, the Coracle and Punt turbidite sands are replaced by claystones of equivalent age. The principle risk on Badger is the up dip seal which requires a stratigraphic pinch out of the sand. It is interpreted that the Coracle channel sand flows eastwards and southwards, crossing the main basin bounding fault into 12/30 and following the axis of subsidence along the north side into 13/26 where an accumulative facies is apparent on the seismic. The channel margin therefore forms the up dip seal to the west. Up thrown fault seal is required to the south and there is some risk here of breach against late Jurassic sands.
Hydrocarbon type, Source maturity and migration: The source rock is the Kimmeridge Clay Formation that is mature on the south side of the Ross fault. Migration to the west is focused upon the West Bank High through Late Jurassic Burns sands and the Punt system itself. The expected hydrocarbon type is not certain; in the 13/26a-2 Dee discovery the Punt contains gas that was tested at 22.3mmcfpd but there is oil in the Punt system at Hobby Field further to the west. Because Badger is located on the northern side of the West Bank High an oil case is proposed since dry gas in the Lower Cretaceous is not the norm in this area.
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