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BP applies for pool rules for Orion Prudhoe Bay Schrader Bluff accumulation estimated at 1.1-1.8 billion barrels in place, 20-25 percent recovery with waterflood Kristen Nelson Petroleum News Editor-in-Chief
Prudhoe Bay field operator BP Exploration (Alaska) has applied to the Alaska Oil and Gas Conservation Commission for pool rules for the Orion pool, a Schrader Bluff formation satellite in the northwest corner of Prudhoe Bay. BP owns a 26.35 percent working interest in Orion. Co-owners are ExxonMobil (36.4 percent), ConocoPhillips Alaska (36.07 percent), Chevron USA (1.16 percent) and Forest Oil (0.02 percent).
BP told the state that estimates of original oil in place at Orion are 845 million to 1.41 billion barrels in the O sands and 225 million to 375 million barrels in the N sands, a total of 1.07 billion to 1.785 billion barrels in place. Gas in place is estimated at 170-280 billion cubic feet in the O sands, 40-65 bcf in the N sands, a total of 210-345 bcf.
Primary depletion would recover approximately 5-10 percent of the oil in place in the development area.
“Waterflood has been identified as the main development option for Orion,” BP told the state, and said that with waterflood the recovery is expected to be 20-25 percent of the oil in place. Total wells are estimated at 40-80 injectors and 30-45 producers. With waterflood, production from Orion is expected to peak at 30,000 to 50,000 barrels per day, with peak waterflood injection rates of 100,000-125,000 barrels per day.
The field owners said in September that they estimate potential recovery at more than 200 million barrels of 16-to-23 degree API viscous crude oil. Production will be processed through existing Prudhoe Bay facilities.
BP said early production tests at Orion produced lower than expected rates, but that good results from the V-202 well suggest that “drilling with oil-based mud and ensuring that the well bore stays in the best quality rock can offset formation damage.” Accumulation first drilled in 1968 Orion overlies the Prudhoe Bay oil pool in the vicinity of Prudhoe Bay unit L, V, W and Z pads, and overlies the Borealis oil pool in the vicinity of Prudhoe Bay unit pads L and V. Orion was first drilled and logged in 1968 at the Kuparuk State No. 1 well, and in 1998 sidewall cores were taken at the Northwest Eileen 2-01 well, confirming hydrocarbons in the Schrader Bluff sands. There are 10 distinct N and O sand intervals at Orion, BP said.
Commerciality of Orion was confirmed in April 2002 when the V-201 well was completed and fracture stimulated in the O sands, and the owners said this September that they would develop the accumulation.
Production began from the V-202 well in June 2002, and BP said additional laterals will be added to the V-202 “to make it a high-angle trilateral producer.” Initial production of 21.5 API degree oil Initial production from Orion was in April 2002 from the V-201 well: 21.5 API degree oil at 1,080 barrels per day. That well was converted to jet pump and after 16 months was producing 600 bpd and has produced approximately 174 million barrels. In the V-201 well, the top of the Orion pool is at 4,126 feet true vertical depth sub sea, and the base of the pool at 4,650 feet true vertical depth sub sea.
The V-202, with a 3,000-foot single lateral, initially tested at 7,100 bpd in July 2003. After a month the well was producing 2,000 bpd and had produced more than 100 million barrels.
“V-202 had the highest initial rate of any Schrader Bluff viscous-oil development well drilled to date,” BP said.
Because favorable results have been obtained with horizontal multilateral wells, BP told the state, the initial development plan for Orion is based primarily on multilateral wells.
Orion will be developed in phases, with the first phase focused “on developing and establishing waterflood operations in areas with good seismic quality and/or well control.” Development results from phase I will be used to refine plans for the second and third phases. Phase I from V, L and W pads Phase I will include both development and appraisal wells, BP said, “designed to provide early production and injection well performance information, while evaluating the fluid and rock quality in previously untested areas of the field.”
There are two V-pad wells on production, and a dual Borealis-Orion water injector.
A tri-lateral producer, L-200, will be drilled from the L pad in late 2003-early 2004, with immediate waterflood support available from an existing Borealis-Orion water injector. Additional tri-lateral producers and vertical or multi-lateral injectors are planned for L pad in 2004.
There are no Orion wells at W pad, and tri-lateral producers and vertical or multi-lateral injectors are being considered there in 2004 to “test the southeast area of the field, which had relatively poor well control and no recent test data.”
In Phase II, BP said, it will drill locations it can reach from existing gravel pads. Plans call for an additional 10-20 producers and 20-40 injectors in the L, V, and Z pad areas, plus approximately two producers and four to eight injectors in the area accessible from W pad.
BP said the second phase of the program “is designed to access areas with poor fault resolution, including higher-risk, structurally complex areas.”
Phase III will target areas to the northwest that cannot be reached from L pad, and BP said it is evaluating the installation of I pad to access that area. The company estimates that 10-20 producers and 20-40 injectors would be drilled in the third phase.
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