Oil Search has applied to the Alaska Division of Oil and Gas to form the Quokka unit in an area where there have been a number of discoveries, most recently Mitquq, drilled in 2020.
Quokka is east of Pikka, and like that unit, the primary focus is the Nanushuk.
The application, signed by Bruce Dingeman, president of Oil Search (Alaska) LLC, was filed on behalf of working interest owners OSA, Repsol E&P USA LLC and Finnex LLC. OSA would be the unit operator.
OSA and Repsol hold the majority of the acreage in the proposed unit, anchored in the north by the Placer unit (acquired by Oil Search and Repsol from ASRC Exploration in 2021), extending south for more than 30 miles and including some 70 state oil and gas leases.
Dingeman said the three WIOs collectively control 100% of working interest in the leases. Acreage includes the Placer leases which are pending assignments from ASRC Exploration, and a number of leases pending assignment from Armstrong Energy and GMT Exploration (jointly owned leases) and from Armstrong Energy.
The majority of the Quokka leases are held 51% of OSA and 49% by Repsol, while Finnex has a 100% interest in four leases.
Wells in proposed unit area
Eleven wells have been drilled in the proposed Quokka unit, Dingeman said: Kookpuk 1 (1967), Cirque 1 (1992), Atlas 1 and 1A (2001), Cirque 4 (2002), Placer 1 (2004), Placer 2 (2004), Cronus 1 (2006), Placer 3 (2016) and Mitquq 1 and ST 1 (2020).
He said four of the wells discovered oil, “collectively identifying producible reservoirs in three different stratigraphic formations - the Kuparuk C (Placer 1, Placer 3), the Alpine C (Mitquq 1), and the Nanushuk 9 (Mitquq 1 and Mitquq 1 ST).”
He said additional wells within the proposed unit area demonstrate the prospectivity of the Nanushuk formation within the proposed unit.
WIOs and their predecessors have also conducted other major exploration activities, Dingeman said, including licensing of various seismic datasets “and extensive work assembling, reprocessing, merging, and improving these datasets.”
OSA is proposing a five-year unit term, beginning Dec. 1, 2021, with the plan of exploration for the unit setting out proposed activity in the initial five-year period, including “seismic processing and interpretation of recently acquired 3D seismic and integration into prior seismic datasets, well-tie analysis, and extensive static and dynamic modeling.”
One appraisal or exploration well is planned in the unit by the second quarter of 2026, according to the unit plan of exploration. It would be drilled to a depth sufficient to test the Nanushuk section (5,500 feet true vertical depth), with exact well location to be determined from results of earlier work done under the exploration plan, “and/or informed by third-party exploration results on adjacent leases.”
Reservoir potential
In an attachment providing information on prior exploration activities and potential hydrocarbon accumulations, OSA said the proposed unit overlies three proven reservoirs - Mitquq NT9 (Nanushuk), Placer Kuparuk C and Alpine C, as well as other potential hydrocarbon accumulations.
OSA said Nanushuk has long been known to host at least one oil reservoir, that at Umiat, and gas reservoirs in the Brooks Range foothills, “but economically viable reservoirs on the crest and flanks of the Barrow Arch region went unrecognized until the relatively minor Qannik field in the Colville River Unit was appraised by numerous wells targeting underlying Jurassic and Cretaceous reservoirs.”
The U.S. Navy Fish Creek test well 1, drilled in 1949, encountered Shublik-sourced heavy oil, 14 degrees API, in the upper Nanushuk above 3,000 feet, “setting the expectation that Nanushuk oils might all be problematically biodegraded.”
OSA said that even after Qannik was developed, piggybacking off the existing developments at Alpine, “hopes for Nanushuk exploration potential remained low until Repsol’s serendipitous discovery of the much thicker and more aerially extensive Pikka Nanushuk accumulation.”
Appraisal of the Pikka-Horseshoe/Narwhal trend, together with ConocoPhillips’ discovery and appraisal of the Willow and West Willow fields, and the 2020 Mitquq and Stirrup discoveries “have changed perspectives on Nanushuk play potential.”
The Mitquq NT9 (Nanushuk) reservoir has a gas cap and oil column, but no known oil-water contract. In Mitquq 1, net pay reaches 218 feet of oil plus 24 feet of gas; the sidetrack found 146 feet of oil and 26 feet of gas.
The Torok formation in the proposed Quokka unit hosts potential hydrocarbon accumulations, “some of which have been penetrated by exploration wells,” OSA said.
ConocoPhillips has established sustained Torok production in the Colville River unit Nanuq-Nanuq participating area, and “variable success” has been achieved at the Oooguruk unit Torok PA and the Kuparuk unit Torok PA.
Kuparuk C is present at Placer, acquired by OSA and Repsol in 2021. OSA said the companies “propose integrating the acreage and its reservoirs into the northernmost part of the Quokka Unit.”
Also present in the proposed unit is the Alpine C oil and gas reservoir, discovered in Mitquq 1 with a 52-foot thick reservoir and 31 feet of net oil pay and 21 feet of gas cap.
