AOGCC approves Fiord field pool rules

Miscible water-alternating-gas enhanced oil recovery planned, with 17 wells, at Alpine satellite north of main field

By Kristen Nelson

Petroleum News

Total estimated recovery from Alpine satellite Fiord will be 32 million to 113 million barrels of oil, field operator ConocoPhillips Alaska told the Alaska Oil and Gas Conservation Commission in its application for pool rules.

The commission approved rules for Fiord July 21; production began at the field’s drill site, CD-3, Aug. 8 and first oil from the field reached the Alpine processing facility at CD-1 Aug. 9 (see story in Aug. 13 issue of Petroleum News).

The company said peak rates from Fiord are expected to range between about 14,000 and 41,000 barrels of oil per day, waterflood injection between 23,000 and 59,000 barrels of water per day and miscible hydrocarbon gas injection at between 16 million and 42 million standard cubic feet of gas per day.

Seventeen wells are expected to be drilled, all horizontal: 12 to the Nechelik zone (six producers and six injectors) and five wells (three producers and two injectors) to the Kuparuk zone.

Development is planned as a miscible water-alternating-gas enhanced oil recovery process, with cyclic injection of water and enriched miscible injectant into the pool. The water displaces oil in the reservoir, replacing produced fluids to maintain reservoir pressure and control gas channeling, the commission said. The enriched MI injection mixes with and mobilizes residual oil in the reservoir, allowing it to be displaced by injected water.

Oil in place is estimated at 80 million to 190 million barrels; with only primary recovery estimated production is 10 million to 32 million barrels. Adding waterflood would produce an additional 12 million to 47 million barrels; the addition of MI adds another 10 million to 24 million barrels.

The commission agreed with ConocoPhillips’ request in its November 2005 application for pool rules to treat the Nechelik and Kuparuk zones as a single oil pool, the Fiord, within the Colville River field. (See story in Dec. 25, 2005, issue of Petroleum News.) It said the “zones are in direct contact in the northern part of the pool and in hydraulic communication with each other. The two reservoirs contain a common accumulation of oil and therefore constitute a single oil pool.”

In a description of Fiord geology the commission said the Fiord oil pool “encompasses two reservoir sandstone intervals that are in direct contact and in hydraulic communication within the oil column.” The deeper reservoir interval, Nechelik, lies within the Kingak formation; the shallower, Kuparuk zone, lies within the Kuparuk formation.

The best quality reservoir stone occurs near the top of the Nechelik, the commission said. Nechelik porosity averages about 16 percent. There is a wedge of non-reservoir shale and sandstone between the Nechelik and Kuparuk. There is a thin interval of Alpine sandstone in the wedge of sediments separating the Nechelik and Kuparuk zones at the southeastern edge, about five feet thick in the Fiord No. 2 exploration well. The commission said there was some oil staining, but in this area, more than two miles from the nearest Alpine development well, “the Alpine sandstone appears to be of fair to poor reservoir quality.”

The Kuparuk zone is typically less than five feet thick and has an average porosity of about 22 percent.

The commission said well log and seismic information indicates the oil in the Fiord pool is trapped by both structural and stratigraphic elements. Analyses from the Fiord No. 5 and Fiord No. 4 wells “indicate that oils trapped within the Nechelik and Kuparuk zones are likely the same oil,” the commission said, with crude oil measuring between 28.6 and 31.3 degrees API gravity.