Discovery of the Jansz-Io field in 2000 established the presence of the Jurassic W. Spectabilis fairway in the deep-water Exmouth Plateau, North Carnarvon Basin. In conjunction with the regionally prolific Triassic Mungaroo gas play, this assisted in exciting record bid levels during the 2006 Gazettal of offsetting acreage, with the award of WA-390-P to Hess for a work commitment of 3,135 km2 3D seismic data and 16 exploration wells. In the first phase of exploration the 3D acquisition was completed and four wells positioned using 2D data were drilled in 2007.

Three of these, Glencoe–1, Briseis–1 and Nimblefoot–1, were discoveries in the post-Callovian interval, with Briseis–1 encountering additional gas pay in the Triassic Mungaroo Formation. The W. Spectabilis sandstones encountered in Glencoe–1 were analogous to those encountered in the Jansz–1 discovery well, 75 km to the northeast.

These are interpreted to have been deposited in a shallow marine environment with accommodation space controlled primarily by the relict topography of the Triassic fault blocks. In contrast, Nimblefoot–1 and Briseis–1 both encountered gas pay in deep-water sandstones of Berriasian age.

These are interpreted to be delta-front turbidites sourced from the Barrow delta to the south, analogous to the Scarborough gas field, but in fault-bounded traps in which fragments of the hanging wall systems have been preserved in the degraded footwalls of major faults. Both play types are characterised by classic seismic amplitude and AVO anomalies.