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Northstar: 3 million barrels in 2012 Report says Beaufort Sea field averaged 8,300 barrels per day; has some production from two new oil pools as well as main reservoir Alan Bailey Petroleum News
The Northstar oil field, operating from an artificial island in Alaska’s Beaufort Sea, produced a total of 3 million barrels of oil in 2012, with an average daily oil production rate of 8,300 barrels, according to the Northstar unit 10th plan of development, submitted by field operator BP to the Alaska Department of Natural Resources, or DNR, at the end of March. According to data published by the Alaska Oil and Gas Conservation Commission, by the end of March the field had achieved an accumulated production of 157 million barrels of oil since startup in 2001.
Production from Northstar peaked at an average of 68,700 barrels in 2004 and has steadily declined since then.
The field is owned 98.6 percent by BP Exploration (Alaska) Inc. and 1.4 percent by Murphy Exploration (Alaska) Inc.
Field reservoirs Northstar’s main oil reservoir lies in the Ivishak formation, in rocks equivalent to the main reservoir of the giant Prudhoe Bay field on the mainland to the south. Some oil also comes from an adjacent part of the Shublik formation, a rock unit that forms a major oil source for many North Slope oil fields.
The rate of production decline at Northstar in recent years has been alleviated somewhat by oil production from two reservoirs outside the original, main oil reservoir. One of these reservoirs, referred to as “Fido,” consists of a separate and distinct geologic structure in the northeast sector of the Northstar unit, in rocks equivalent to the main Northstar reservoir. The other reservoir, directly above the main producing reservoir, consists of a sand unit in the Kuparuk formation, equivalent to part of the assemblage of reservoir sands in the Kuparuk River field to the southwest.
Following a 2011 DNR directive to contract the Northstar unit to match the field’s “participating area,” the area containing the field’s producing reservoir, DNR gave BP the opportunity to define a separate Fido participating area, to ensure that the Fido oil accumulation would remain within the unit. The agency also told BP to define a participating area for the Kuparuk reservoir.
Federal land The Northstar unit straddles both state and federal land on the Beaufort Sea continental shelf, with the Fido structure being located entirely in federal land. And according to BP’s plan of development, in January 2012 the company applied to the federal Bureau of Safety and Environmental Enforcement, or BSEE, and to DNR to form a Fido participating area, with BSEE subsequently approving the participating area in June 2012.
According to the participating area application, Fido consists of a “four-way faulted trap,” penetrated by a single production well and completely isolated from the main Northstar reservoir. Relatively uniform rocks with few barriers to oil flow in the reservoir enable excellent oil recovery, while subsurface water drives production without the need for water to be injected from the surface, the application says.
According to the participating area application, the Fido accumulation went into production in May 2008 with an initial flow rate of 8,000 barrels per day, with that rate declining to about 600 barrels per day by January 2012. By October 2011 the accumulation had produced 2.2 million barrels of oil, with an estimated ultimate recovery of 2.9 to 3.4 million barrels.
Hooligan The Northstar plan of development says that in June 2012 BP applied to the state and federal agencies for another participating area, called Hooligan, to encompass the Kuparuk reservoir. The agencies have yet to issue a decision on this application.
The Hooligan application says that production from the Kuparuk reservoir started in November 2010, when BP placed a plug above the level of the Ivishak in one of the Northstar production wells, while also opening a sliding sleeve in the well in the Kuparuk sand. And with several Northstar wells penetrating the Kuparuk en route to the deeper Ivishak, BP has been able to use well data in combination with seismic data to map out the structure of the “Hooligan field,” while inferring the locations of various fluid contacts within the structure.
Production has continued using that single modified well. By April 2012 the Kuparuk reservoir had produced about 13 billion feet of natural gas and about 620,000 barrels of condensate, with the gas being injected into the Northstar Ivishak reservoir for pressure maintenance, the Hooligan participating area application says. Production rates in June 2012 were 26 million cubic feet per day of gas and 970 barrels per day of condensate, the application says.
Currently the Kuparuk production comes only from a single sand unit, referred to as the Kuparuk C sand. But there is a possible future opportunity for production from another sand, the Kuparuk A, the application says.
And recent upgrade work on the Northstar production island would appear to express confidence in the continuing value of the Northstar field as a whole — BP has now completed the relocation and replacement of base camp facilities on the Northstar island, the plan of development says.
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