Prudhoe Bay producers now expect to ultimately recover 14.1 million-14.2 billion barrels of oil from the giant Alaska North Slope field, about 60% of the estimated oil in place in the reservoir rock, company managers said.
That’s up from 9.6 billion barrels, a 40% recovery, estimated when Prudhoe was first discovered in 1968.

“The Prudhoe producers have done a very good job of maximizing recovery, and they’ve had a very high quality reservoir to work with,” said Mark Myers, Alaska’s Commissioner of Natural Resources.
To get this result, Myers said, the field operators have employed innovative new production and drilling technologies, some of them invented or first applied on the slope.

These include multi-lateral wells, or several wells drilled underground off a single well from the surface; use of low-cost coiled-tubing units for drilling; extended-reach horizontal production wells and “four dimensional” seismic, the commissioner said.

Bruce Laughlin, BP’s manager for Alaska reservoir development, said gas re-injection for pressure maintenance and a miscible injectant made with natural gas liquids used in enhanced oil recovery, have also been major factors in improved recovery, along with a field waterflood.
BP is the operator and part-owner of Prudhoe Bay. Other owners include ConocoPhillips and ExxonMobil.
As an oil field, Prudhoe is showing its age. The Prudhoe Oil Pool, the field’s largest oil reservoir, is now producing about 250,000 b/d, or one-sixth of its original rate of 1.5 million b/d. Its wells once produced 10,000 b/d or more but many are now at 1,000 b/d or less.
The reservoir is still, however, the largest slope producer and one of the largest US producing fields. It is also the economic lynchpin of the North Slope producing half of the overall slope output of about 500,000 b/d. It would be economically difficult to operate the Trans Alaska Pipeline System without Prudhoe, Laughlin said.

Prudhoe still has a long life ahead as an oil producer but the producers are now planning a new role for the field, as a gas producer. Prudhoe holds about 23 trillion cubic feet of gas and would supply about 75 percent of the 3.5 billion cubic feet of gas needed daily for the planned $50 billion-plus Alaska LNG Project (the remaining 25 percent of gas will come from Point Thomson, a new gas field being developed east of Prudhoe Bay).

As it is with oil, Prudhoe will be the lynchpin for the gas pipeline and LNG project.

Production of Prudhoe’s gas will result in an additional 3.5 to 3.6 billion barrels of oil equivalent (i.e. gas expressed in terms of equivalent energy as crude oil), Laughlin said.

In the long run, thanks to gas production, there will be more oil recovery from Prudhoe because infrastructure maintenance and operations will be shared between gas and oil production.

Maintenance costs are now being spread across a diminished number of oil barrels being produced, which will decline further as production drops.

After 2025, when the gas project is to start up, gas will help shoulder those costs. That will extend Prudhoe’s life as an oil producer.