West Sak project production already up

Drilling at 1E under way, with production already up from 10,000 bpd to 18,000 bpd; by project end in 2007, 40,000 bpd expected

Kristen Nelson

Petroleum News Editor-in-Chief

Drilling at pad 1E, part of the $500 million West Sak expansion announced by ConocoPhillips and BP in August, has already kicked up production levels at the North Slope Kuparuk River unit accumulation.

Darren Jones, vice president of ConocoPhillips Alaska’s greater Kuparuk business unit, told the Alaska Support Industry Alliance Oct. 21 that 1E drilling will be complete by May and has already kicked up West Sak production from 10,000 barrels per day to 18,000 bpd. Drilling at 1J will start about when 1E drilling is complete and run through September 2007, with West Sak production expected to be more than 40,000 bpd by 2007.

The 1E and 1J development project, however, is “just the first step on the path to commercializing the North Slope’s heavy oil,” Jones said.

There are some 23 billion barrels of heavy oil on the North Slope, he said, “sitting above the Kuparuk and Prudhoe reservoirs.” Those 23 billion barrels are mainly in West Sak at Kuparuk, Schrader Bluff at Milne Point, and Orion and Polaris in Prudhoe Bay; the shallower Ugnu is predominantly at Kuparuk and Milne.

The 23 billion barrels, he said, are “split approximately 50-50 between the Ugnu and the West Sak-Schrader Bluff,” with 15 billion to 16 billion of those barrels at Kuparuk, again split roughly 50-50 between West Sak and the shallower Ugnu.

Jones said the reason the oil hasn’t already been developed isn’t “so much that it’s heavy oil” but because “it’s cold and heavy oil — and therefore very viscous.” The oil is cold because the formations are close to the surface, with 1,800 feet of permafrost above them: formation temperatures range from 40 F in the shallowest reservoirs to 90 F in the deepest.

Flow rate is “inversely proportional to viscosity,” he said, and while conventional North Slope oil has roughly the viscosity of water, the best West Sak oil “has the viscosity of cold olive oil … and the Ugnu has the viscosity of maple syrup.” Viscous oil also impedes the efficiency of conventional recovery methods such as waterflood.

And a final challenge: heavier oil sells at a discount to conventional oils.

Technology advances the key

Sand control has also been an issue, he said, because the heavy oil reservoirs are “not as well compacted and cemented as the deeper reservoirs” and tend to produce sand with the oil. Screens were used to try to control sand down hole, “but laboratory work and field experience told us that because some of the sand grains are very fine, like flour, even the best screens couldn’t keep all of the sand out.” There were two additional problems with screens, he said: they restricted the flow of oil and they cost about a million dollars per lateral.

“So the 1E and 1J development is designed to handle the sand on the surface, rather than trying to keep it back down hole.” Higher rate production allows an increase in the distance between wells, reducing the cost per barrels, and gas-lift backup capability has been added “so that we can continue to produce a well even if you have failures of electric submersible pumps.”

Well designs have also changed “radically” since the late 1990s, Jones said: “We’re now drilling … tri-lateral wells with individual lateral lengths of up to 6,000 feet,” and undulating laterals through the deepest sands.

We’ve “increased the amount of oil we can access by a factor of three, due to the ability to drill extended reach wells,” an advance Jones attributed to rotary steerable systems, torque reduction tools, lubricity additives in mud systems and better engineering through modeling.

Owners’ technical cooperation critical

The West Sak 1E and 1J “project is really just a start.”

The next move will be to areas of Kuparuk that have similar viscosity to the West Sak oil at 1E and 1J, but, we “can see that there are 13 to 14 billion barrels of the heavy oil resource that need further technology for it to be developable. We’re looking for technical solutions,” Jones said, but those additional barrels “represent huge technical and economic challenges,” and producing them may require incentives as well as technology advances.

And while the $500 million 1E and 1J West Sak project is the “biggest ever investment in North Slope heavy oil,” it’s not the first.

“Since West Sak was discovered in 1971 the Kuparuk River unit owners have spent $500 million on technology and experimentation in the field,” and continue to look for technology to allow production of heavier oil. Development “won’t come cheap,” he said.