Abstract

Pikka field is located in the Colville foreland basin on the North Slope of Alaska. This prolific petroleum producing province contains several giant fields, including North America’s largest oil field, Prudhoe Bay field. Although the area was considered past its prime for exploration, in 2013 a joint exploration venture consisting of Armstrong Energy, LLC, Repsol, and GMT Exploration announced a major discovery in the Qugruk 3 well where approximately 250 ft (76 m) of net pay was encountered in the Cretaceous Nanushuk Formation, a little explored interval that is stratigraphically younger than the historically productive zones. Subsequent appraisal of the discovery has delineated a large, hydrocarbon-charged, stratigraphic trap that includes what is now the Pikka Unit. In 2017, the Horseshoe 1 and 1A wells were drilled 22 mi (35.4 km) south of the discovery well and confirmed giant status for Pikka field. The Pikka discovery established the Nanushuk as a new play and refocused the industry’s attention on exploration on the North Slope.

The Nanushuk Formation represents the topset and upper foreset segments of a series of prograding clinothems that were deposited in a foreland basin during the Lower Cretaceous. Sandstone reservoirs at Pikka field are found in two individual clinothem sequences informally named the Nanushuk 3 and Nanushuk 2 zones that were deposited on a subaqueous shelf and shelf-edge delta. Net pay thickness is variable with less than 50 ft (15 m) present on the shelf part of the reservoir and up to 250 ft (76 m) in the expanded section outboard, or seaward, of the underlying shelf edge. Porosity ranges up to 29% (20% average) with permeability up to 690 md (47 md average). Oil gravity ranges from 23° to 32.5° API depending on elevation within the hydrocarbon column. To date, 740 ft (226 m) of hydrocarbon column has been proven. Preliminary estimates indicate an original oil in place (OOIP) volume for the total field area of 9.7 to 14.8 billion barrels of oil (BO) with a range of 1.9–4.4 billion BO recoverable. Most of the reserves occur in the expanded section of the Nanushuk 3 zone. The Qannik oil pool within the Colville River Unit currently produces from Nanushuk 2 equivalent shelf sandstones and appears to be part of the overall accumulation.

The Pikka Unit portion of the field will be developed using a phased project concept that is focused on initial delivery of an 80,000 BOPD single drill site development. FEED will start in early 2021 with first oil planned for 2025. Additional drill sites and expansion of the processing facilities will be added in the future as warranted. ConocoPhillips is currently developing their portion of Pikka field from existing infrastructure within the Colville River Unit. Independent reserve auditor, Ryder Scott, has certified gross 2C contingent recoverable oil resources of 767.6 million barrels for the Pikka Unit portion of the field (Oil Search Press Release, 2021).