Northstar Drilling—Delivering the First Arctic Offshore Development

Abstract

Summary Northstar is the first arctic offshore development that is not accessible by road for most of the year and does not have fixed-wing air support. The implications of limited access to a 400×400-ft island are enormous. Successful completion of the first drilling season at Northstar is a significant milestone marked by detailed design and execution as well as pure determination. Many of the challenges were anticipated and accounted for, while many others were not. These challenges included environmental hurdles, logistical constraints, and commissioning the rig and the grind and inject (G&I) facility on an accelerated schedule. The first arctic offshore development delivered its first barrels of oil as per schedule on 2 November 2001. Now comes the next challenge - drilling to improve the profitability of this unique Alaskan project. Introduction Northstar is BP's newest field development on Alaska's North Slope. The field is currently being drilled, and production has just commenced from the man-made Seal Island. Northstar is approximately 6 miles north of Prudhoe Bay in the Beaufort Sea (see Fig. 1). The island was built in approximately 40 ft of water on the remains of Seal Island, which was used for the original discovery/ appraisal wells. The field encompasses roughly 60 square miles and contains an estimated 176 million barrels of recoverable reserves. Northstar will be the first development in Alaska that will be produced from both state and federal leases, with oversight from both the Alaska Oil and Gas Conservation Commission and the Mineral Management Service. Physical preparations for drilling operations at Northstar began in the winter of 1999/2000. Activities included island and pipeline construction, significant rig modifications, service company contracting, team selection, and well planning. During the open-water season of 2000, actual drilling operations commenced with the mobilization (by barge) of the rig, service contractor equipment, and enough consumables for four wells. Following the mobilization, the rig and all island equipment were successfully commissioned, and the first well was spudded on 16 December 2000. The Challenges Drilling from a very small man-made island located in Alaska's harsh arctic environment presents many challenges, all requiring individual attention while still maintaining continuity between all facets of the operation. The previous BP development project on the North Slope, which helped define a "small footprint," was Badami. This development made use of main production sites that measured approximately 900×1,200 ft. Fig. 2 illustrates the relative size comparison of Northstar to the total Badami infrastructure. Northstar measures 400×400 ft, and this reduction in the footprint has impacted every aspect of Northstar's operations. At the very center of the challenges are health, safety, and environment (HSE). Northstar presents new problems to solve with respect to the health and safety of the rig team. One of the largest concerns is the ability to completely evacuate the island at any given time in the event of an emergency. The North Slope's short open-water season and limited ice-road season dictate the need to provide a means of evacuation available regardless of the time of year. To accommodate this need, two arctic, amphibious-tracked vehicles (see Fig. 3) were contracted and built to specifications, allowing all 94 of the island's occupants to be evacuated in an emergency during any of the Beaufort Sea's open-water, broken-ice, or continuous-ice conditions. Despite being Coast Guard approved and tested, a ride in the arctic, amphibious-tracked vehicles is a rare treat, as the extreme motions of an amusement park ride are achieved in a completely sealed and windowless vessel with 23 other passengers. It is for good reason that drills are generally scheduled at least 3 hours after any meal! Another safety and environmental concern that must be managed on an ongoing basis is the potential for contact with arctic wildlife, primarily polar bears. Because of the island's location among the pack ice, polar bears are far more prevalent than in any other area of the North Slope. Programs have been put in place to carefully control the disposal of all food waste on the island to limit attractants and to monitor and alert occupants to the presence of wildlife adjacent to the island. Although numerous sightings of polar bears and other wildlife have occurred, none have yet entered the island itself. The environmental challenges of the Northstar project are no less daunting. As a zero-discharge development, Northstar relies heavily on a single waste-disposal well that is permitted for disposal of all Class I and Class II waste, including injection of all drill cuttings. This is only the second well to be permitted and drilled as a Class I slurry injection well in Alaska. Management of this multiwaste stream-disposal well is key. Any disruption in the disposal stream of the injection well results in shutdown of both drilling and production operations. Thus far, no downtime has occurred as a result of injection loss. The well also acts as the sole produced-water injector for the development. Strict air-emissions requirements at Northstar have required converting the rig engines to natural gas with eventual high line power operation once the island's gas turbine-fired generators are on line. Similar engine and horse-power restrictions on all sources have prompted the need for modifications beyond the rig to include electrification of Schlumberger's trailer-mounted wireline unit as well as Halliburton's bulk cement facility and pumping skid. Every operation on the island is closely monitored and coordinated between drilling and operations to ensure all air-quality requirements are met. Within Northstar's environmental management system, there are more than 1,000 stipulations that must be met as conditions of BP's license to operate. Logistics at Northstar present the largest challenge to both HSE and operational efficiency. Resupply of consumables can only be accomplished during two periods at Northstar - the open-water and ice-road seasons that last approximately 2 and 2 1/2 months, respectively. These two limited seasons require upfront planning and detailed lay-down plans to allow up to 3.5 wells' worth of consumables to be staged on the island between resupply periods.