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Continuing development at Alpine field Latest ConocoPhillips plan describes strategies to tease more oil out of existing reservoirs while company gears up for CD-5 Alan Bailey Petroleum News
ConocoPhillips’ Alpine oil field and its satellite fields in the Colville River unit, to the west of the Prudhoe Bay and Kuparuk River fields, has over the years become a significant success story in the annals of North Slope oil production. Having first gone into production in 2000, the original field has proved a stepping out point for neighboring modest-sized oil accumulations and is now set to provide an infrastructure link to the first oil development in the National Petroleum Reserve-Alaska.
According to data from the Alaska Oil and Gas Conservation Commission, the fields in the unit had delivered a cumulative total of 445 million barrels of oil by the end of March this year.
CD-5 In its latest Colville River unit status update report, sent to the Alaska Department of Natural Resources in March, ConocoPhillips outlined the continuing development that the company is undertaking in the unit. The company’s Colville River unit plans include its Alpine West development, known as CD-5, in the National Petroleum Reserve-Alaska — following U.S. Army Corps of Engineers approval of a wetlands permit for this development, ConocoPhillips and its partners have sanctioned funding for the development.
“Final engineering for the Alpine West CD-5 project is complete and construction will begin in Q1 2014 following long-lead procurement and prefabrication work in 2013,” the status report said. “Drilling operations will commence in mid-2015 followed by startup in December 2015.”
Development at CD-5, using a new gravel pad and access gravel road, will mirror the horizontal drilling strategy employed elsewhere in the Colville River unit, with a series of six production wells drilled horizontally through the reservoir formation, paralleled by seven injection wells. The injection wells will drive oil production using a technique called MWAG, involving the alternating injection of water and miscible injectant into the reservoir. Miscible injectant consists of a mixture of natural gas and natural gas liquids.
Four oil pools The existing fields within the Colville River unit consist of the original Alpine oil pool and three satellite pools: Fiord, Nanuq and Qannik. Development has taken place from four gravel pads, CD-1, CD-2, CD-3 and CD-4, with the all of the fields sharing a central processing facility on the CD-1 pad.
The Alpine field itself, originally developed from the CD-1 and CD-2 pads, produces light oil from two relatively fine-grained Jurassic sand horizons, termed the A sands and the C sands. Subsequent development has also taken place from CD-4, the report said.
The Fiord satellite field came online in August 2006 from the CD-3 pad, with two reservoir zones, one in the Nechelik sand of the Jurassic Kingak formation and the other in the Kuparuk C sand of Cretaceous age. Nanuq went into production in November 2006 from the CD-4 pad, producing from Kuparuk C sands, equivalent to those at Fiord, and from shallower and younger Nanuq sands. The Nanuq Kuparuk pool has since been classified as part of the main Alpine oil pool. Qannik came on line in July 2008 from the CD-2 pad, accessing a sandstone oil reservoir at a higher subsurface level than the other satellite reservoirs.
Horizontal wells Development of all of the oil pools within the Colville River unit has primarily involved combinations of horizontal production and injection wells. Qannik and Nanuq use waterflood to flush oil from the underground reservoirs, while all of the other pools, including the main Alpine field, use MWAG techniques, the ConocoPhillips report said. However, some older injection patterns in the Alpine and Nanuq Kuparuk pools have reached a level of maturity where only waterflood is now used. A gas cap in the Qannik satellite also helps to drive production from that oil pool, the report said.
In 2010 ConocoPhillips conducted a 3-D seismic survey in the Colville River unit, to obtain high resolution images of the subsurface and to provide information about subsurface changes as a consequence of oil and gas production. And in 2012 the company drilled a data acquisition borehole from the CD-4 pad, to obtain samples of some of the shallower rocks, as a means of gaining mechanical data of assistance when drilling, the report said.
During 2013 ConocoPhillips anticipates offsetting natural production decline in the Alpine field through techniques such as MWAG management, well workovers and drilling in development opportunities at the field’s periphery. The company also expects to stimulate up to 10 wells through hydraulic fracturing — four fracture stimulations were conducted in 2012 and these significantly increased oil production, the report said.
Drilling opportunities Drilling opportunities in 2013-14 include seven new injection wells and five new production wells, mainly in peripheral areas in the southwestern and eastern parts of the field. A well planned for the CD-1 pad would test a target to the northeast of the main field. And success in new development drilling in the eastern part of the field could result in further exploitation of this area, the report said.
No new wells are planned for the Nanuq Kuparuk reservoir within the Alpine field in 2013, although performance from this reservoir continues to exceed expectations, the report said.
To date, 11 production wells and 10 injection wells have been completed in the Fiord Nechelik zone, with two wells being completed in 2012, the report said. ConocoPhillips anticipates drilling one well in 2013, two wells in 2014 and one well in 2015 in this zone, the report said. In 2012 the Fiord Kuparuk zone had three active production wells and three active injection wells — in 2013 ConocoPhillips plans to drill two new production wells and to convert one existing production well to an injector, the report said.
The Nanuq pool currently has three production wells and two injection wells. No new wells were drilled in 2012, but several new wells are planned for 2013, the report said.
The Qannik pool has three water injection wells and six production wells, with no new wells drilled in 2012 and none planned for 2013.
Other efforts to maximize production in the Colville River unit include the treatment of some wells to remediate downhole well scaling. And ConocoPhillips has been conducting an extensive reservoir pressure monitoring program, using downhole pressure gauges, to optimize reservoir flood arrangements and prepare for drilling operations, the report said.
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