Beaufort Sea

Setting industry standards for Arctic design and leading the development of exploration platforms

Exploration activities in the Beaufort Sea are challenged by a short, open water season and multi-year ice. Multi-year ice has survived at least one melt season, may be much thicker than first-year ice, and typically continues to grow over time. To address these challenges, ExxonMobil undertook significant efforts to develop ice design criteria for exploration and production structures.

In 1973, ExxonMobil built the world’s largest ice-test basin in Calgary to study interactions between ice and offshore structures. Five years later, at Prudhoe Bay, we conducted the world’s largest ice-strength characterization tests on level ice.

Due in part to the knowledge gained from these studies, we have participated in drilling 44 shallow-water exploration wells in the Canadian and U.S. Beaufort Sea since the early 1970s. These wells were drilled using gravel island, ice island, Caisson Retained Island (CRI), Concrete Island Drilling System (CIDS), Molikpaq and Single Steel Drilling Caisson (SSDC) systems. We are the only company that has application experience with all of them.

ExxonMobil pioneered the use of gravel islands for exploration drilling activities, installing the world’s first gravel island in the Canadian Beaufort Sea in 1973 and completing the deepest-water gravel island in 1980. We have also developed industry standards for gravel island technology in the Arctic and held the first industry-wide seminar on the topic.

In addition to our work with gravel islands, we also led an ice island experiment in the U.S. Beaufort Sea from 1978 to 1979. The results of that experiment led to the development of spray-ice construction methodologies and criteria for efficient and cost-effective implementation. In 1989, ExxonMobil built the world’s largest ice-spray exploration island, Nipterk P-32, in an area of the Canadian Beaufort Sea outside the protection of the barrier islands, where significant daily ice movements are common.

The CRI structure, which requires less gravel than a traditional gravel island and is less expensive and faster to install, was developed by ExxonMobil and used in the Beaufort Sea in 1983. In order to further reduce  construction costs, we also developed a reusable gravity-based structure called CIDS, first used in 1984 at the Antares prospect in the U.S. Beaufort Sea.

ExxonMobil used the heavily instrumented Molikpaq structure, a steel caisson filled with granular material, during Beaufort Sea exploration. In the winter of 1985-86, Molikpaq experienced the most severe ice conditions any man-made structure had ever sus-tained, including multi-year ice up to seven meters (21 feet) thick. The data collected on this structure significantly enhanced ExxonMobil’s ice-load calculation methods and design criteria.

Between 1986 and 1987, ExxonMobil also drilled two exploration wells in the U.S. Beaufort Sea using an SSDC — an ice-strengthened, converted supertanker that rests on a mobile steel platform, allowing for year-round drilling.

The combination of extensive, fundamental studies of ice mechanics, ice data collection and our unique operational experience has provided us with the unparalleled expertise in ice-load calculations that we have subsequently applied in other Arctic environments.

First Beaufort Sea offshore production system

ExxonMobil is a co-venturer in the Endicott oil field located in the Alaskan Beaufort Sea, about 13 kilometers  eight miles) east of Prudhoe Bay. Key Arctic offshore technical challenges included a short open-water season and severe ice conditions in winter.

To address the issues of severe ice, currents and ice scouring, two gravel production islands were built. These were the first applications of our gravel island technology for offshore Arctic production. The Endicott Production Island started up on October 3, 1987, as the first offshore Beaufort Sea production system, and continues to operate today.