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Providing coverage of Alaska and northern Canada's oil and gas industry
April 2011

Vol. 16, No. 14 Week of April 03, 2011

ExxonMobil in Alaska: Setting standards for Arctic design

For 45 years ExxonMobil has been committed to northern technology research, development

Petroleum News

Exploration activities in the Beaufort Sea are challenged by a short open water season and multiyear ice. Multiyear ice that 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; an effort that actually began 45 years ago with Mobil’s offshore, ice-resistant Granite Point platform, installed in Alaska’s Cook Inlet basin in 1966.

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, the company conducted the world’s largest ice-strength characterization tests on level ice.

Due in part to the knowledge gained from these studies, Exxon has participated in drilling 44 shallow-water exploration wells in the Canadian and Alaska Beaufort Sea since the early 1970s. The wells were drilled using gravel island, ice island, caisson retained island or CRI, concrete island drilling system or CIDS, Molikpaq and single steel drilling caisson or SSDC systems. Exxon says it is the only company that has application experience with all of them.

Exxon 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.

The company developed industry standards for gravel island technology in the Arctic and held the first industry-wide seminar on the topic.

In addition to its work with gravel islands, Exxon also led an ice island experiment in the Alaska 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, Exxon 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.

In 1981-82 Exxon drilled two wells offshore the North Slope at Beechey Point, utilizing a gravel island.

The CRI structure, which requires less gravel than a traditional gravel island and is less expensive and faster to install, was developed by Exxon and used in the Beaufort Sea in 1983.

In order to further reduce construction costs, the company also developed a reusable gravity-based structure called CIDS, first used in 1984, and again in 1985, at the Antares prospect in Alaska’s Beaufort Sea.

That drilling was followed by use of CIDS at the Orion prospect, also off Alaska in the Beaufort.

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

Between 1986 and 1987, Exxon drilled two exploration wells in Alaska’s Beaufort Sea using the 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 its unique operational experience has provided Exxon with the unparalleled expertise in ice load calculations that it has subsequently applied in other Arctic environments.

Editor’s note: Although none of the Beaufort Sea wells mentioned above proved commercial, in 1978 another leaseholder, Standard Alaska Production Company, struck oil at Endicott, where Exxon also held leases (see Exxon press release on page 73).






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