Nikaitchuq North plan
Eni proposes two extended reach wells from Spy Island starting next winter
Eni US Operating Co. has filed a plan of operations amendment with Alaska’s Division of Oil and Gas proposing the drilling of two extended reach exploration wells from Spy Island into the Nikaitchuq North prospect, in the federal outer continental shelf of the Beaufort Sea. The prospect lies immediately north of the operating Nikaitchuq field, which is in state waters of the Beaufort. The drilling would take place from an existing Nikaitchuq field pad on Spy Island, a man-made gravel island about three miles off Oliktok Point.
The surface locations of the two wells, the NN01 and NN02 wells, would be adjacent the existing row of production wells on the Spy Island drill site, Eni’s plan amendment says. Two strings of conductor pipe, well houses and new well containment structures will be needed for the wells, with the wells being drilled along S-shaped trajectories into the target rocks. Eni plans to drill the wells to vertical depths of 8,000 feet in federal blocks OCSY-1757 block 6423 and OCS-Y-1754 block 6374. The extreme extended reach of the wells will result in measured depths of about 34,000 feet, the plan says.
Further drillingEni told the division that, depending on the initial results of the drilling, the company may take further action, starting with bypass drilling for rock coring. From either well, following an analysis of well logs and core data, the company may later drill a 1,000-foot horizontal sidetrack well for production testing. The production testing would involve the flowback of oil to surface test equipment on the Spy Island pad.
The drilling of the NN01 well is scheduled to start at the beginning of December this year, potentially continuing until the beginning of March. Eni may then drill the second well, the NN02 well, during the summer of 2018. Depending on results, Eni may conduct the horizontal sidetrack drilling during the winter of 2018-19.
Eni will presumably require an especially powerful drilling rig for the extreme extended reach drilling involved in its Nikaitchuq North project. The company’s plan anticipates the use of the Doyon Rig 15, or a similar rig.
The company is in the process of seeking approval from the federal Bureau of Ocean Energy Management for an exploration plan involving the proposed wells. The project will require a drilling permit from the Alaska Oil and Gas Conservation Commission.
At the end of February the federal Bureau of Safety and Environmental Enforcement approved the formation of the Harrison Bay Block 6423 unit, a unit encompassing 13 federal leases that include the Nikaitchuq North prospect.
Schrader Bluff formationThe producing oil reservoir in the Nikaitchuq field under state waters of the Beaufort Sea lies in the upper Cretaceous OA sands of the Schrader Bluff formation, although Eni has also been considering development in another sand unit, the Schrader Bluff N sands. The Schrader Bluff formation is known to extend a long way out into the Beaufort Sea continental shelf. The formation lies within the Brookian sequence, the youngest and shallowest of the major North Slope petroleum bearing rock sequences.
Development of the Schrader Bluff in the Nikaitchuq field has been challenging because of the compartmentalized nature of the sands and the relatively viscous oil. Eni has been using a combination of horizontal injection and production wells, with both electric submersible pumps and water injection boosting oil production. The company has been threading horizontal, multilateral sidetrack wells through the sand bodies.
On the continental shelf the Brookian typically lies on top of older rocks that have been faulted into large blocks. The Brookian sands are though to thicken in the more downthrown rock sections between the faults.