Another Prudhoe Bay unit satellite, Raven on the northeastern edge of the unit, has been approved by the state as a participating area.
The Alaska Division of Oil and Gas said Dec. 21 that it has approved an application from BP Exploration (Alaska) — on behalf of itself and the other Prudhoe Bay unit owners — to form a participating area for the Raven accumulation.
Raven is offshore Heald Point west of Endicott.
The division said in its decision that the Raven participating area encompasses oil-bearing sands within the Permo-Triassic interval, including the Ivishak sandstone and Sag River formation underlying the Niakuk Kuparuk reservoir. While the intervening Shublik formation may eventually contribute to Raven PA hydrocarbon production, the division said “that formation is generally considered to be a low permeability carbonate” and no Shublik development is currently planned at Raven.
There are two producing wells and one injector in the Raven PA, which has been producing under tract operation approval. Production from Raven is combined with other production from Greater Point McIntyre and is processed at the Lisburne Production Center. The Raven PA encompasses 1,615 acres and covers portions of sections 24-26 and 36 of township 12 north, range 15 east and portions of sections 29-31 of T12N-R16E, Umiat Meridian. The Raven PA includes portions of three state leases, ADLs 34625, 34630 and 34635.
Following pre-application meetings in late 2005 and early 2006, BP applied in February 2006 to form the Raven PA. The division said it delayed approving the application pending its decision on BP’s application to combine the Niakuk and West Niakuk participating areas into the combined Niakuk PA, an application which was approved in early December (see story in Dec. 23 issue of Petroleum News, www.petroleumnews.com/pnads/651173571.shtml).
Raven below NiakukThe Raven reservoirs lie below the Niakuk oil pool within the boundaries of the Prudhoe Bay unit. The Raven PA is defined by the top Sag River formation structural closure. Seismic coverage over the area was shot by Western Geophysical for Sohio/BP in 1986. BP subsequently produced structure maps, but the division said: “An uncertainty resides in the accuracy of any depth map derived from seismic data for an area that is located in the onshore-offshore transition zone, as is the case of the” Raven participating area.
The Raven oil pool correlates with the interval found at 10,628 feet measured depth to 11,165 feet measured depth in the BP Niakuk 5 well.
The division said data in BP’s application indicates both the Sag River and Ivishak are capable of producing hydrocarbons in paying quantities.
There are numerous small accumulations of oil and gas tested or produced from the Ivishak sandstone north of the Prudhoe Bay bounding fault — Northstar, North Prudhoe Bay, Eider and in the Gwydyr Bay area. Oil and gas have also been produced from the Sag River formation north of Prudhoe at the Milne Point unit and North Prudhoe Bay. “These accumulations, like the Raven reservoirs, are structural closures,” the division said.
There is faulting within the Raven PA with four areas defined — the north and south fault blocks and the east and south areas — with the bulk of proven reserves in the north and south fault blocks.
Previous wells at NiakukBoth exploratory and development wells penetrated the Sag River and Ivishak sandstone in the immediate area of the Raven PA.
The March 1976 Niakuk 1A contains partial cores of Sag River and Ivishak sandstone with minor hydrocarbon shows in the Sak River; the Ivishak in this well is down dip and wet.
The Sag River is faulted out at the Niakuk 4 well drilled in early 1985 but the Ivishak sandstone was logged and cored.
In March 1985 the Niakuk 5 initially tested 32 API gravity oil from the Sag River formation.
An extended Sag River production test was done from NK-43 in 2001 and produced a high gas-oil-ration condensate, 49 degree API, and minor black oil.
Oil in placeThe division’s decision does not include estimates of how much oil will be produced from Raven but does contain estimates of original oil in place for the Ivishak sandstone of 6.9 million to 11.4 million barrels, condensate at 2.3 million to 3.8 million barrels for a total of 9.2 million to 15.2 million barrels in place.
For the Sag River, the OOIP estimate is 3.5 million to 5.8 million barrels, the condensate 1.3 million to 2.2 million barrels for a total of 4.8 million to 8 million barrels.
OOIP totals for the Raven PA are 10.4 million to 17.2 million barrels of oil and 3.6 million to 6 million barrels of condensate for a total of 14 million to 23.2 million barrels.
Original gas in place for the Raven PA is estimated at 71.5 billion to 119 billion cubic feet: 55.8 bcf to 92.9 bcf is free gas and 15.7 bcf to 26.1 bcf is solution gas.
Alaska Oil and Gas Conservation Commission production statistics show monthly production from Raven in November of 42,090 barrels of oil, 101,946 barrels of water and 295 million cubic feet of natural gas from two producing completions, with cumulative oil production of 1.57 million barrels of oil, more than half a million barrels of water and 7.7 billion cubic feet of natural gas.
Natural gas from Raven, other than gas extracted as natural gas liquids and blended with crude oil for shipment down the trans-Alaska oil pipeline, is used for unit operations or injected into another formation underlying the unit area.
Development from Heald Point drill padBP is developing the Raven PA from the Heald Point drill pad, used to produce oil and gas from Niakuk. Raven production will be processed through the Lisburne Production Center. “Raven production will be constrained by the gas and water handling capacity at the LPC,” the division said. Raven PA water injection will be from Lisburne and gas lift gas will be supplied from the Lisburne high-pressure gas injection system at the Lisburne L5 drill site.
Raven shares infrastructure support facilities with the Lisburne participating area and the Prudhoe Bay initial participating area.
The surface use agreement for Heald Point is in dispute. The division said the Oenga heirs, who own surface rights to Heald Point, assert — through their attorney — that the current lease language does not authorize Raven development.
The heirs do not object to exploration or development of North Slope oil reserves, but, the division said, are concerned that surface lease agreements should authorize the use of facilities before production begins and assert the lease with BP authorizes production from Niakuk, but not from any other pool and have requested delay of approval of the Raven PA until the surface lease between the Onega heirs and BP is modified.
The division said it “will not further delay” its decision on the Raven PA because of requests from the Onega heirs, noting that the Raven PA decision “deals with subsurface issues surrounding the establishment of the participating area,” while the issue raised by the attorney for the Onega heirs “focuses on resolution of a private dispute regarding individual surface rights,” a separate issue from subsurface development. That dispute, the division said, “must be resolved between BPXA and the Onega heirs.”