Conoco keeps the oil flowing at Alpine
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New drilling around periphery of the field opens up new production possibilities, while development of the satellites also continues
Alan Bailey Petroleum News
As with any oil field, the focus at the Alpine field and its satellites in the Colville River unit on Alaska’s North Slope is on maximizing field value by slowing as much as possible the inevitable production decline that follows peak field production.
And the most recent progress report that unit operator ConocoPhillips has filed with the Alaska Department of Natural Resources describes the steps that the company is taking to keep as much as oil as possible flowing from Alpine and its satellites for export through the trans-Alaska oil pipeline, while also looking for new oil development opportunities within and near the unit boundary — Alpine, one of the success stories of modern North Slope exploration, has become a stepping out point for developing new, modest sized oil accumulations at the western side of the central North Slope and west into the National Petroleum Reserve-Alaska.
Started 2000 The Alpine field, owned 78 percent by ConocoPhillips and 22 percent by Anadarko Petroleum Corp., first went into operation in 2000, producing light crude oil from two relatively fine-grained Jurassic sand horizons, termed the A sands and C sands, in what geologists refer to as the Beaufortian sequence of rocks. The development strategy involved the use of horizontal wells that would run through the sands, with some wells producing the oil and other wells injecting water to shift the oil through the reservoir rocks. Development drilling was done from two gravel pads: the CD1 pad, holding the field processing facilities, and the CD2 pad some three miles to the west.
And in the years after the Alpine startup three smaller satellite fields — Fiord, Nanuq and Qannik — have all gone into production within the Colville River unit, all using the same general development strategy of interwoven horizontal production and injector wells, and all producing oil through the Alpine field production facilities.
Fiord, the first of the satellite fields, went into production in August 2006 from two connected reservoir zones, one in the Nechelik sand of the Jurassic Kingak formation and the other in the Cretaceous Kuparuk C sand. The field was developed from a new gravel pad, the CD3 pad, about five miles north of CD1.
Nanuq came on line in November 2006 using wells drilled from the CD4 gravel pad, about four miles south of CD1. This satellite field produces oil from two horizons: the Kuparuk C sands, equivalent to those at Fiord, and the shallower and younger Nanuq sands, equivalent to the reservoirs of the Meltwater and Tarn satellite fields of the Kuparuk field to the east, and lying in a rock sequence that geologists refer to as the Brookian.
Qannik, which came online in July 2008, uses wells drilled from the extended CD2 pad. The Qannik oil pool lies in a sandstone unit above the Alpine, Nanuq and Fiord reservoirs.
ConocoPhillips next planned step-out from Alpine, the CD-5 or Alpine West development, lies in the extreme east of the National Petroleum Reserve-Alaska. This development has been stymied by a refusal by the U.S. Army Corps of Engineers to allow the construction of a bridge across the Nigliq Channel of the Colville River. Development at CD-5 could lead to further step-outs to the west, to tackle some known, modest-sized oil accumulations in the NPR-A Moose’s Tooth unit.
Continuing development While work progressed on developing the Alpine satellite fields, development of the central Alpine field continued, with ConocoPhillips completing all of the originally planned field wells by 2005.
The company has implemented an oil recovery method known as miscible water alternating gas, or MWAG, at the field, the progress report says. MWAG involves the mixing of natural gas liquids with natural gas from the field, and injecting the resultant “miscible injectant” in alternation with water. The water consists of both water produced from the field and seawater imported from the Kuparuk field seawater system.
And, following an increasing demand for injected water in both Alpine and its satellites, ConocoPhillips increased the Alpine water pumping capacity in 2009, the report says.
Monitoring of well pressures at Alpine has revealed unexpected pressure declines resulting from mineral scaling in the wells. In 2009 ConocoPhillips initiated a scale inhibitor program in the field and also began fracture stimulating some wells, the report says.
More drilling Development since 2005 has involved new drilling around the periphery of the field, with two wells drilled into the A sands from CD4 in 2006, three A-sand wells completed from CD2 and CD4 in 2007, and an A-sand well drilled from CD2 in 2008.
ConocoPhillips completed eight additional wells on the edge of the Alpine field in 2009, the report says. Those well were drilled from CD1, CD2 and CD4 to extend the field to the northwest, west and southwest. A CD4 well has also encountered C sand of better quality than expected in the southern part of the field, indicating further development potential there.
In 2010 ConocoPhillips plans to drill a well slanting out east from CD1, to test the C sands in that area, the report says.
And the company planned to conduct a new 3-D seismic survey across the Alpine field in 2010, to help identify new drilling opportunities, as well as to gain insights into fluid behavior and pressure changes in the field.
To date, ConocoPhillips has drilled 117 wells in the Alpine field — 58 injector wells, 57 production wells and two waste disposal wells, the report says. In 2009 oil production averaged 58,900 barrels per day.
Satellite development And development has continued in the Alpine satellites.
The report says that the initial phase of development of Fiord is now finished, with all surface facilities completed and 11 horizontal wells drilled, and with production supported by MWAG techniques. A new injector and a new producer well in the Fiord Kuparuk zone were completed in 2009 and ConocoPhillips plans five further wells for 2010. The company anticipates drilling sidetrack wells from two existing wells in the winter of 2010, the report says. The average production rate in 2009 was 7,300 barrels of oil per day.
Nanuq has been a good news, bad news story, with the Nanuq Kuparuk reservoir exceeding performance expectations while the shallower Nanuq reservoir has proved disappointing. Average 2009 production from the Kuparuk sands came in at 16,700 barrels per day, while the Nanuq produced just 500 barrels per day. Production from both reservoirs involves MWAG techniques.
ConocoPhillips had suspended new drilling into the Nanuq reservoir pending an investigation into reservoir performance but plans to finish a new horizontal production well in 2010 — the current plan involves using a phased approach to developing the complex Nanuq reservoir, the report says.
However, no new wells were drilled in either the Nanuq or Kuparuk reservoirs in 2009 and ConocoPhillips plans to drill one new horizontal production well in the Kuparuk in 2010.
Performance of the Qannik satellite has met expectations, with an average daily production of 2,700 barrels of oil in 2009. ConocoPhillips has so far developed 5,000 acres of the Qannik reservoir using eight new horizontal wells and one existing exploration well, with six of the wells operating as producers and three as water injectors, the report says.
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