|
Alaska’s Kuparuk field remains formidable Operator ConocoPhillips has extensive plans for the North Slope giant, ranked as the third largest producing U.S. oil field Wesley Loy For Petroleum News
Kuparuk is Prudhoe Bay’s big little brother. Since its December 1981 startup, the Kuparuk River field on Alaska’s central North Slope has produced 2.19 billion barrels of oil.
That’s an enormous volume, though it pales in comparison to neighboring Prudhoe, which has produced well over 11 billion barrels so far.
Kuparuk averaged 104,145 barrels per day in 2009.
It’s the nation’s third largest producing oil field behind No. 1 Prudhoe and Shell’s offshore Mars-Ursa development in the Gulf of Mexico, the latest Energy Information Administration ranking shows.
Kuparuk, like Prudhoe, is a declining field.
But operator ConocoPhillips Alaska Inc. is working to squeeze every possible drop out of Kuparuk and its satellite fields — West Sak, Tarn, Meltwater and Tabasco. These satellites produced an additional 37,600 barrels per day in 2009.
ConocoPhillips owns about 55 percent of Kuparuk, with BP holding 39 percent, Chevron 5 percent and ExxonMobil the rest.
So what happened at Kuparuk in 2009, and what’s in store for the future?
Here’s a review of the annual update ConocoPhillips submitted to the state on June 30.
The Kuparuk field The Kuparuk field is developed from 44 drill sites, with 808 active wells at the end of 2009 including 436 producers, 208 water injectors and 164 water alternating gas injectors.
Among accomplishments in 2009, ConocoPhillips says it implemented a nine-well coiled-tubing drilling program generating a “peak incremental oil rate” of 4,300 barrels per day. The company says 21 laterals were drilled and completed in the wells.
A workover program added 6,000 barrels per day.
Optimizing Kuparuk output is a delicate dance involving primary production, waterflooding, miscible gas enhanced oil recovery, and immiscible gas flooding, ConocoPhillips says.
To some extent, Kuparuk is dependent on its big neighbor to the east, Prudhoe, and this dependency likely will increase.
During 2009, Kuparuk imported an average of 18,391 barrels per day of Prudhoe natural gas liquids to make miscible injectant, which greatly enhances production.
Kuparuk faces a looming problem — insufficient gas. Field gas production is expected to decline significantly in coming years, which will leave Kuparuk short of gas for enhanced oil recovery and to fuel field operations.
“The most technically feasible known alternative gas source is Prudhoe Bay,” says the ConocoPhillips update. Prudhoe, unlike Kuparuk, has a vast gas cap.
Most likely, gas imports from Prudhoe Bay will begin around 2015.
“The plan is to utilize imported Prudhoe gas as fuel gas only and not introduce any of this gas into the production system, either by injection or in the gas lift system,” the update says. “This is due to corrosion concerns relating to the relatively high CO2 content (10-12%) of Prudhoe gas.”
Spending plans ConocoPhillips says its Kuparuk development plan “assumes the current business climate of increased regulation and taxation will continue, increasing field operating costs. For example, the transition to Ultra Low Sulfur Diesel use in 2009 added tens of millions of dollars to Kuparuk’s annual operating costs.”
Still, the company anticipates extensive investments.
Seismic analysis has revealed “a significant number of leads for infill or sidetrack drilling,” the Kuparuk update says. “Candidate wells developed from these leads will be a mix of ‘grass root’ wells, rotary sidetracks and coiled-tubing sidetracks, depending on the volume of expected oil recovery and the design and operational status of proximal wells.”
The “large portfolio” of potential coiled-tubing drilling candidates spawned the new Nabors rig CDR2-AC, custom-built for the North Slope, the update says.
Although considerable drilling is set for 2010 and 2011, no new drill sites are planned.
ConocoPhillips is considering a low-salinity waterflood pilot project using the trademarked LoSal process at drill site 2X, with injection possibly starting by 2014.
As for field maintenance, the 2008 introduction of smart pigging to look for corrosion in water injection lines has resulted in the shut-in of several lines for repair or replacement. Pigging is expected to wrap up by late 2010.
ConocoPhillips has numerous projects ongoing to either restore water injection or boost water availability and pumping capacity.
West Sak and Tarn Of Kuparuk’s four satellites, West Sak and Tarn are the biggest producers.
West Sak is a vast heavy oil deposit that overlays the Kuparuk field.
West Sak produced an average of 18,866 barrels per day in 2009, and has tallied about 46 million barrels over its lifetime. At year’s end, the field had 44 active producer wells and 46 water injectors on six drill sites.
Waterflooding the reservoir to maintain pressure and improve sweep is the main enhanced oil recovery method used for the West Sak oil pool, ConocoPhillips says. Waterflood performance has been good, although 2009 saw three troublesome “rapid water breakthrough events” that created “high conductive pathways between an injector and a producer.”
A project sanctioned in 2004 at $500 million, the drill site 1J development, is now complete, and thus “the pace of future West Sak development has slowed,” the ConocoPhillips update says.
Infill drilling is planned for late 2011 or early 2012 at drill site 1E.
Activity appears more robust at the Tarn satellite, located southwest of the Kuparuk field.
Tarn produced 14,063 barrels per day in 2009 via 53 development wells on two drill sites. The field, which began production in 1999, has produced almost 100 million barrels of oil, tops among the Kuparuk satellites.
Four new Tarn wells were put on production in 2009 or 2010, with recent tests as high as 844 barrels per day. That was the 2N-305A well, described as a rotary sidetrack.
Lots more drilling is planned.
“More than 15 new wells and sidetracks could be drilled as part of a future infill and peripheral development drilling program,” the ConocoPhillips update says. “Targeted areas include the thinner distal lobes that previously were considered uneconomic.”
One well under consideration for 2011 “may be drilled as a horizontal well with multi-stage frac completion. This would be the first application of this technology at Tarn.”
Meltwater and Tabasco Two remaining Kuparuk satellites, Meltwater and Tabasco, contribute smaller volumes of oil.
Meltwater, about 10 miles south of Tarn, began production in 2001 and made 2,715 barrels of oil per day in 2009. The field has 19 wells on a single drill site, and over its lifetime has produced 14.1 million barrels.
Meltwater is a challenge, with sand bodies that are “highly discontinuous with structural barriers that limit fluid movement through the reservoir,” the ConocoPhillips update says. “It is clear from well performance that connectivity between injection and production wells is considerably less than originally perceived.”
In October 2009, the water injection line to the Meltwater field was taken out of service due to corrosion concerns. Up until that time, Meltwater was undergoing an alternating cycle of miscible gas and water injection to maximize recovery from the reservoir.
With original oil in place of 222 million barrels, Meltwater “shows a large incremental target for additional development,” the update says. A 3-D seismic survey of Meltwater was completed in 2008, and “horizontal or undulating wells to help connect multiple reservoir sands will be considered.”
Tabasco, a heavy oil field on Kuparuk’s western flank, has 12 development wells and produced 1,948 barrels a day in 2009. Since startup in 1998 it has produced 15.6 million barrels.
Geological and reservoir simulation models will help “evaluate alternative recovery strategies and additional development opportunities” for Tabasco, which the operator now waterfloods.
| 