ConocoPhillips Alaska is getting ready to put the Narwhal accumulation in the Colville River unit online and has applied to the state and Arctic Slope Regional Corp. for approval of the Narwhal participating area. A PA defines the area within a unit from which specific production comes.
The proposed PA is in the southeast corner of the CRU, where ConocoPhillips drilled the Putu 2 and Putu 2A wells, adjacent to Pikka, where Oil Search and Repsol are working to develop the Nanushuk. Narwhal is a Brookian Nanushuk sand, ConocoPhillips said in its PA application.
Existing PAs at the Colville River unit, which came online in 2000, include Alpine, Fiord, Nanuq and Qannik.
In its application, filed Nov. 12, the company said it plans to begin sustained production from the Narwhal PA as early as this December, pending approval of the PA application.
Putu 2, Putu 2A
ConocoPhillips said prior exploration activities in the area include the Putu 2 and Putu 2A, drilled in the first quarter of 2018. The Putu 2 reached total depth in the Narwhal. “A total of 751 gross feet of Narwhal was drilled,” the company said.
Putu 2 and Putu 2A met the initial well commitments required for the CRU fifth expansion area.
Putu 2A was fracture stimulated and had a test peak of 2,900 barrels of oil per day.
ConocoPhillips said Putu 2 and Putu 2A were the first wells drilled in the Colville River unit “to find significant Narwhal thickness and reservoir quality.”
Based on the Putu wells, the company announced the Narwhal discovery, estimated to contain between 100 million and 350 million barrels of oil equivalent. Willow and Narwhal are different sediment deposits within the Nanushuk formation, with Willow being older.
In the fourth quarter of 2018 and the first quarter of 2019 ConocoPhillips drilled the CD4-595PH and CD4-595 wells. The CD4-595PH reached total depth in the Narwhal, penetrating 675 feet of gross Narwhal; the well was not tested.
The CD4-595 horizontal well was sidetracked from the CD4-595PH and was fracture stimulated flow tested, peaking at 3,000 bpd with 26 degree API gravity oil; a subsequent flow test peaked at 4,700 bpd and stabilized at 2,500 bpd.
The CD4-594PH1 and horizontal sidetrack CD4-594 injector were drilled in the fourth quarter of 2019.
The CD4-594PH1 found 430 feet of gross Narwhal; it was not tested.
The CD4-594 horizontal, a sidetrack from the CD4-594PH1, was flow tested at 2,500 bpd and then converted to injection.
ConocoPhillips said the Narwhal “has been penetrated in the intermediate hole section of several wells as part of exploration and development of deeper reservoir targets at CD4,” with gross thickness in those penetrations from 30 to 45 feet. The Narwhal was not tested in those penetrations.
Plan of development
ConocoPhillips said the Narwhal, which the company described as a Brookian Nanushuk sand, will initially be developed from CD4, an Alpine satellite pad some 4 miles southwest of the Alpine Central Processing Facility.
CD4 was constructed in 2005 for Alpine, Nanuq and Kuparuk development and is being extended beginning in the 2021-22 winter season to add additional Narwhal well slots (see story in Sept. 5 issue of Petroleum News).
The company said the CD4-595 and CD4-594 appraisal wells were drilled in 2018 and 2019 “in the Narwhal reservoir to better understand the reservoir and to test the technical feasibility of extended reach drilling at shallow depth,” with initial test production in 2019 and 2020.
Sustained Narwhal production is expected to begin in December from CD4-595.
The company said initial plans call for drilling up to 12 Narwhal wells from CD4 in addition to the two existing wells, with two Narwhal horizontal producers and two Narwhal horizontal injectors possible within two years of commencement of sustain production. But any of those wells could be moved to the 2022-23 schedule “as rig optimization/utilization dictates.”
Narwhal production will go to the Alpine processing facility and sales-quality crude will be transported to the trans-Alaska oil pipeline via the Alpine Oil Pipeline and Kuparuk Oil Pipeline.
EWAG
ConocoPhillips said Narwhal will be developed using an enriched water alternating gas process.
The Alaska Oil and Gas Conservation Commission approved a pilot enhanced recovery injection project in the Narwhal reservoir in December 2019 (see story in Jan. 5, 2020, issue of Petroleum News).
ConocoPhillips told the commission in its application that Narwhal is expected to be developed as a line drive water alternating gas flood with horizontal producers and injectors.
In its order approving the pilot the commission said that since the Narwhal reservoir is still in the appraisal stage, a formal pool has not been defined.
“The Narwhal Reservoir sands are broadly age equivalent to the Nanushuk Group,” AOGCC said, and noted that ConocoPhillips’ proposed a definition of the reservoir as the accumulation of oil common to and correlating with the accumulation found in the Qugruk 3 well from 4,192 to 5,152 feet measured depth.
Since the reservoir is still being appraised no in place or recoverable reserves information is available, the commission said, but “Modeling indicates recoveries of less than 5% without injection support and approximately 30% under waterflood.”
CD4, CD8
ConocoPhillips said Narwhal development would continue from CD4 and a future pad, referred to as CD8, targeting Narwhal in the fifth CRU expansion area.
“The current basis of design development concept for CD8 includes a new gravel pad connected by road back to CD4, with associated production and injection piping connected back to ACF,” with 20 to 40 wells in the current concept, depending on expanded knowledge of the reservoir and learnings from 2020-22 Narwhal production.
The company said production from CD8 could begin as early as 2028.
