A 50-50 joint venture of South Australian explorer Strike Energy Ltd. and Scotland-based independent Warrego Energy Ltd. has made a natural gas discovery with the West Erregulla-2 well in the onshore Perth basin about 1,000 m above its primary target.
The gas was found within a 74-m section of the Wagina Sandstone from 4,106 m to 4,180 m. There is potential for further Wagina reservoir which Strike, as operator of the JV, says means that the Basal Wagina which is the formal secondary target for the well has yet to be encountered.
The company said the sudden influx of overpressured gas into the well while drilling through the Wagina exceeded expectations and required mud-weight changes to reestablish stable well conditions. The increased mud weight, however, made attempts to gather reservoir pressures and samples unsuccessful.
Credible logging results were obtained from one 2½-m section at the top of the Wagina section that indicated a 14.2% porosity. This upper section coincided with a large drilling break, clean porous sands, and high-pressure gas flows over the 6-m section 4,111-4,117 m. The gas was recovered to surface and diverted to flare.
West Erregulla-2 is drilling on towards the basal Wagina and has yet to encounter water wet sands.
The well’s primary target of Kingia and High Cliff sands are expected in the final (production) hole section which will be drilled to a nominal total depth of 5,200 m.
West Erregulla-2 is being drilled in permit EP 469 and is targeting analogous Permian-age gas sands of similar size and structure to the Waitsia gas discovery 16 km northwest.
The West Erregulla prospect also lies 9 km east of Beharra Springs gas field where the Permian Wagina Sand is the main reservoir.
The first well, West Erregulla-1, was drilled in 1990 by Barrack Energy and found a net gas pay of 26 m but flowed only minor gas to surface. That well was located 11 km west of the original Erregulla-1 and Erregulla-2 wells drilled by West Australian Petroleum in the mid-1960-70s which had a minor oil flow to surface.
Warrego Energy was awarded 100% of permit EP 469 in 2010. Two subsequent partners withdrew in 2016 and Warrego farmed out a 50% interest and operatorship of the permit to Strike Energy in June 2018 in a deal where Strike would drill and complete one well (West Erregulla-2) and complete geological and geophysical work up to a maximum of $11 million (Aus.).
The commercial potential of a gas discovery in West Erregulla is enhanced by its proximity to the Dampier-Bunbury gas trunk line about 10 km west.