Norwest Energy NL, Perth, reported an encouraging early flow rate of 350 Mscfd of gas from Permian Carynginia shale at its Arrowsmith-2 well on EP413 in the Perth basin of Western Australia.
The company recorded the 350 Mscfd rate on several occasions since the well commenced flowback on Feb. 15, an encouraging sign given that a large percentage of the frac fluid remains in the formation, Norwest Energy said.
The Carynginia had only a limited flowback period in the 2012 hydraulic fracture stimulation program due to a tight operational timeline (OGJ Online, Aug. 23, 2012).
The Carynginia is 250 m thick in the vicinity of Arrowsmith-2 and is a primary target. It is the most typical shale formation in the basin and is demonstrated to be laterally extensive. Shale gas potential in the northern Perth basin is estimated at 59 tcf, Norwest Energy noted.
Next to be tested are the Irwin River coal measure and High Cliff tight sandstone intervals, both of Permian age. The three-formation test program is expected to last as long as 4 months.
Arrowsmith-2 was shut-in after Triassic Kockatea shale interval swabbing in early December 2012 to monitor pressure buildup of the fracture stimulated zone and to provide more data for resource estimation. This activity continued until late January 2013 as Norwest awaited equipment to isolate the Kockatea and mill out the plug at the top of the Carynginia.
The Kockatea was considered a secondary target for this program, but the presence of oil cannot be ignored. Independent consultants will conduct further analysis to evaluate any potential the Kockatea may have as an oil producing zone.
Arrowsmith-2, the first unconventional gas well in the northern Perth basin, was drilled in June-July 2011 and intersected 450 m of Kockatea, 250 m of Carynginia, 330 m of Irwin River, and 22 m of High Cliff. Future work is likely to involve 3D seismic and pilot horizontal wells subject to joint venture approval, Norwest Energy said.
In the July-September 2012 stimulation campaign, High Cliff stabilized at 780 Mscfd, Irwin River and Carynginia yielded gas, and Kockatea yielded oil and gas.