ConocoPhillips wants to drill on the blocks in the Chukchi Sea that the company leased in 2008. If everything goes according to plan, one or two wells will be drilled on the Devil’s Paw prospect about 128 km (80 miles) offshore Wainwright, Alaska, during the open-water season in summer 2014.

“In drilling terms, a jackup is ideal for the Chukchi Sea with water depths of 40 m to 42 m (132 ft to 139 ft),” Randall Shafer, ConocoPhillips, said during a presentation (Offshore Technology Conference Paper No. 23745) on “Use of Jackup Drilling Units in Arctic Seas with Potential Ice Incursions During Open-Water Season” at the 2012 Arctic Technology Conference in Houston Dec. 4, 2012.

After looking at semisubmersibles, drillships, and jackups, the company chose a jackup based on higher variable deck load and deck area, a fixed riser to the seabed, surface and seabed BOP controls, and availability.

The initial wells will be drilled in the Chukchi Sea on blocks awarded to ConocoPhillips during Lease Sale 193.

Based on US National Ice Center data from 1996 to 2007, the average open-water season was about 100 days from July through October. Open water for the purpose of evaluating modular offshore drilling units is defined as no ice within 45 km (25 nautical miles) of the proposed well location, Shafer noted.

Ice-alert and ice-management systems are keys to safe operations. All of these systems are designed around the amount of time it takes to secure the well. “It takes us 24 hours to secure a well and jack down the rig. That varies with the depth of the well,” he added. “However, we don’t expect any ice incursions into our area at all. Over the last three years, we haven’t had any ice incursions.”

An added level of safety is provided by a specially designed prepositioned capping device (PCD), which consists of two blind/shear rams and is installed on the wellhead on the seabed. In the unlikely event of loss of primary and secondary control from the surface BOP, the PCD can be activated to regain control of the well either from the drilling rig or a nearby vessel. The PCD system is separate from the rig’s BOP and power source.

ConocoPhillips has been running virtual drilling exercises for three consecutive years timed to the open-water seasons. By July 27, 2012, the ice was 45 km away. In the virtual drilling program, “we spudded the well on July 30 and completed it by Sept. 2,” Shafer explained. “We suspended operations during the drilling as a test and still completed the well. We then moved the rig into the second position and drilled that well too. We moved the rig off location on Oct. 1.”

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