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Field owners apply for pool rules, water flood at Midnight Sun Prudhoe Bay satellite pool will be produced from E Pad, share existing facilities; deeper test planned before one well converted to water injection Kristen Nelson PNA News Editor
Midnight Sun satellite oil field owners plan to develop the 40-60 million barrel oil-in-place accumulation from three wells, two already drilled plus a planned horizontal producer. One of the existing wells will be converted to injection for water flood.
Field operator Phillips Alaska Inc. presented testimony to the Alaska Oil and Gas Conservation Commission June 21 on applications for pool rules and an injection order to develop the North Slope Kuparuk formation accumulation, estimated at 40-60 million barrels in place of 25-29 degree API gravity oil and total gas in place of 100-130 billion cubic feet. Phillips said the free gas volume associated with the gas cap is 60-80 billion standard cubic feet.
The accumulation was discovered in 1997 in the 1 Sambuca well (since renamed the E-100) north of Prudhoe Bay and southwest of Point McIntyre.
Production will be from E pad, from which both wells into the formation have been drilled. The delineation well, the 1 Midnight Sun (since renamed the E-101), was drilled in 1998.
Phillips told the commission that the E-100 was the first well to encounter the Kuparuk River formation in the area; previous exploration well in the area, and wells from nearby pads, have not encountered the Kuparuk formation. Recovery models Phillips said three development options were evaluated for the Midnight Sun pool: primary depletion, estimated to recover 14 percent of original oil in place; upstructure gas injection, estimated to recover 20-27 percent of OOIP; and water flood, estimated at 39 percent recovery for water injection in midfield.
This plan involves conversion of the E-100 well to injection service.
There may be potential for enriched gas injection at Midnight Sun, but Phillips said no enhanced oil recovery evaluations have been initiated. Improved reservoir description and additional field performance would be required before an EOR option can be fully explored, the company said.
The recommended development plan for the Midnight Sun pool is midfield water injection, expected to begin in the third quarter of 2000, with design injection rates of 20,000-25,000 barrels of water per day. Peak production is expected to be in the 8,000-10,000 barrels of oil per day range prior to waterflood breakthrough.
Planned development includes the addition of one upstructure horizontal production well to complete a three-well development of the Midnight Sun pool. Infill drilling and/or peripheral drilling along the eastern margin of the field will be evaluated as field development continues. While initial wells will be on 280 acre spacing, Phillips requested 80 acres spacing in Midnight Sun pool rules to allow for flexibility to respond to conditions as field development proceeds. Deeper test planned In its June testimony, Phillips told the commission the E-100 well, the top of the Kuparuk formation occurs at 7,974 feet total vertical depth and the base occurs at 8,074 feet total vertical depth (11,662 feet and 11,805 feet measured depth, respectively). Phillips said this is the productive interval of the Midnight Sun pool.
Phillips said that in addition to oil in the Kuparuk formation, heavy oil was encountered at 8,107 feet total vertical depth in the E-101 well. A sample measured 10 degrees API. Phillips said the extent of this heavy oil accumulation was not known, and also said there were no plans to develop it at this time.
When the discovery was announced in 1998, then owners ARCO Alaska Inc., Exxon Company USA and BP Exploration (Alaska) Inc. said the E-100 encountered a 100-foot vertical section of oil- and gas-bearing rock in Kuparuk sands at a measured depth of 11,662 and that oil and gas were also found in a 160-foot vertical section of rock in the Sag/Ivishak formation at a measured depth of 12,965 feet. The Kuparuk interval, the Midnight Sun pool, tested approximately 4,000 barrels per day of 29 API gravity oil and 1.5 million standard cubic feet of gas per day. The Sag/Ivishak formation tested 1,400 barrels per day of 24 API gravity oil and 490,000 standard cubic feet of gas per day.
Commissioner Dan Seamount asked Phillips about the Sag/Ivishak test and Phillips said that within a few days the lower interval production was 30-40 percent water, making the lower interval marginal. Phillips said there were no development plans for the Sag/Ivishak, but did tell the commission that the company was applying to test the deeper horizons in the E-100 well before it is converted to water flood. Existing facilities to be used E pad is one of the original Prudhoe Bay drilling pads, Phillips said, and is large enough to accommodate development of the Midnight Sun pool without any additional gravel. Phillips said that wells will be drilled between existing initial participating area wells on the pad.
Water for injection will come from either water wells drilled at E pad, or from produced water from Prudhoe Bay Gathering Center 1. Phillips said Midnight Sun owners are working towards approval to use GC1 produced water as a water source for Midnight Sun.
Future gas lift gas will be obtained from an initial participating area E-pad well, Phillips said. Production from Midnight Sun will be allocated based upon tests until a new metering skid is installed in the third or fourth quarter 2000. Thereafter, Midnight Sun production will be continuously metered prior to combining with initial participating area production.
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