A major find on Alaska’s North Slope has been expanded by exploration drilling this winter.
The Horseshoe exploration well and sidetrack, drilled by operator Armstrong Energy in partnership with Repsol, both found oil in the Nanushuk, Repsol said March 9.
“Repsol and partner Armstrong Energy have made in Alaska the largest U.S. onshore conventional hydrocarbons discovery in 30 years,” Repsol said. It said the Horseshoe 1 and 1A wells “confirm the Nanushuk play as a significant emerging play in Alaska’s North Slope,” extending the play discovered at Pikka by 20 miles.
Repsol said resources currently identified in Repsol and Armstrong blocks in the Nanushuk play amount to some 1.2 billion barrels of recoverable light oil.
“The successive campaigns in the area have added significant new potential to what was previously viewed as a mature basin. Additionally Alaska has significant infrastructure which allows new resources to be developed more efficiently,” Repsol said.
The company said it has been actively exploring in Alaska since 2008 and since 2011 has drilled multiple consecutive discoveries on the North Slope along with partner Armstrong. The base of the acreage position was assembled by Armstrong beginning in 2008 and 2009; the company brought Repsol in as a majority partner in that acreage in 2011. The companies have added to their acreage base in subsequent lease sales and by purchases from other leaseholders.
Repsol: ‘multiple reservoir discoveries’
Repsol operated earlier wells in the exploration program. The company said prior to Horseshoe it was operator on 13 exploration and appraisal wells on the North Slope, which led to “multiple reservoir discoveries” currently included in the Pikka unit.
In August Armstrong transferred a 25 percent working interest in the lease on which Horseshoe is located, and two neighboring leases, to Repsol. The permit for the original well, issued in December, shows the well some 1,500 feet east of the Colville River unit and some 12 miles southwest of Nuiqsut.
The well is on one of a package of leases east of the Meltwater satellite of the Kuparuk River unit which Armstrong Energy acquired from Royale Energy in late 2015.
Earlier this year Armstrong Energy CEO Bill Armstrong said the locations of the Horseshoe wells were determined from a Horseshoe 3-D seismic program.
The Pikka discoveries were made in 2014 and 2015 and development permitting with Armstrong as operator is underway in that area.
Bill Armstrong told Petroleum News in February 2016 that Pikka is possibly a multibillion barrel resource in just two of at least six horizons. Mark Myers, former commission of the Department of Natural Resources, called the original Pikka discovery “amazing.”
Armstrong said last year that peak output from three Pikka pads was estimated at 120,000 bpd, which is the volume Repsol said could come from preliminary development concepts for Pikka, with first production anticipated in 2021.
A draft EIS being prepared by the U.S. Army Corps of Engineers will be released in the middle of this year, the agency said.
Repsol said the Horseshoe 1 discovery well was drilled to a total depth of 6,000 feet and encountered more than 150 feet of net oil pay in several reservoir zones in the Nanushuk section. The Horseshoe 1A sidetrack was drilled to a total depth of 8,215 feet and encountered more than 100 feet of net oil pay in the Nanushuk interval as well, Repsol said.
