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Forest plans EOR at West McArthur River Waterflood expected to help oil recovery; pilot calls for one injection well; three wells currently producing combined 1,270 bpd Kristen Nelson Petroleum News
Forest Oil has applied to the Alaska Oil and Gas Conservation Commission for a pilot waterflood at the West McArthur River unit on the west side of Cook Inlet.
Forest wants to inject water into an offshore oil pool in the Hemlock formation at a depth of 9,251 to 9,438 feet below sea level to improve recovery from the pool, which is in township 8 north and range 14 west of the Seward Meridian. The field is offshore in section 10-8N-14W, SM; it is produced from two onshore pads in 16-8N-14W, SM.
In a May 10 application the company told the commission that there are 11 wells at West McArthur River drilled by the field’s developer Stewart Petroleum Co. and the subsequent owner Forcenergy Inc.
Forest Oil is currently 100 percent working interest owner of the field.
Three wells are producing: West McArthur River unit Nos. 5, 6 and 7ST. Two wells, the Nos. 1A and 2A are suspended, the 4D well was plugged back and is in use as a Class II disposal well and Nos. 1, 2, 3, 3ST and 7 are abandoned.
In addition, the West Foreland Unit No. 2 well was drilled and abandoned by Pan American Petroleum in 1966.
First production in 1991 The WMRU No. 1 was drilled in 1991 with first production in December 1991 and first sustained production in August 1993. The No. 2A would be the initial injection well for the EOR pilot project. It produced from the Hemlock from October 1993 through January 2002 and has been suspended since January 2002.
Forest told the commission the No. 2A well is the farthest down-dip well on the south side of the West McArthur River unit structure “and thus is a prime wellbore to initiate a pilot waterflood from,” and is expected to increase oil recovery from the field’s three producing wells.
Forest said that depending on the success of the pilot EOR, additional wells may be added, sidetracked and/or re-completed as water injection wells to maximize Hemlock oil recovery.
Producing wells hydraulically lifted Current production from the field is some 1,270 barrels of oil per day and 3,350 barrels of water per day. The No. 5 well produces 660 bpd of oil and 900 bpd of water; the No. 6 produces 510 bpd of oil and 1,000 bpd of water; and the No. 7ST produces 100 bpd of oil and 1,450 bpd of water. Because of limited water disposal capacity in the No. 4D well, the No. 7ST is often shut in due to high water cut and relatively low oil production rate, the company said.
With water injection in the No. 2A, Forest told the commission the No. 7ST can be produced continuously.
All produced water from the West McArthur River unit as well as commission-agreed upon alternative water sources such as treated sanitary waste, gray water, produced Hemlock water from the Redoubt unit, produced Tyonek water from West Foreland and storm water from secondary containment areas would be injected, with total injection estimated at 3,000 to 4,000 bpd of water.
The No. 4D well is a Class II disposal well with current injection to the Tyonek formation and has absolutely no enhanced recovery effect on oil production from the West McArthur River unit, the company told the commission.
No estimate of EOR effect Injection is estimated at 3,350 bpd of water, compared to current production of 4,620 bpd (1,270 bpd of oil and 3,350 of water).
“Although this injection will not quite match the reservoir off-take, it is expected to help minimize the reservoir pressure depletion and is expected to enhance the areal sweep efficiency of the Hemlock oil production,” the company said.
It also said that historical data suggests “some degree of a natural water drive exists” at the West McArthur River unit.
Forest did not provide an estimate of the EOR impact of the water injection. It said original oil in place at West McArthur River is estimated at 30-36 million barrels, with cumulative recovery of 11.1 million barrels through April 30, a 31-37 percent recovery rate. Forest said other reservoirs with mature waterfloods have recoveries of as much as 42 percent of OOIP.
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