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Hilcorp wants Northstar gas injection
Company has applied to AOGCC for permission to inject into the Beaufort Sea field’s Kuparuk pool for enhanced oil recovery Alan Bailey Petroleum News
Hilcorp Alaska has applied to the Alaska Oil and Gas Conservation Commission for permission to inject natural gas into the Northstar field’s Kuparuk oil pool for enhanced oil recovery. Depending on the quantity of gas injected, ultimate oil recovery from the pool could increase from 9 million barrels to somewhere between 13 million and 14.6 million barrels, Hilcorp told the commission.
Since Northstar first came into production in 2001, oil has come from a reservoir in the Ivishak formation, equivalent to the main reservoir of the onshore Prudhoe Bay oil field. In 2006 BP, then the Northstar field operator, began testing production from shallower Kuparuk sands. Sustained production from a single well, the NS-08, in the Kuparuk started in 2010.
According to Hilcorp’s application to the AOGCC, Northstar currently has 30 wells, three of which are shut in. Hilcorp continues to produce from the Ivishak, but now produces from Kuparuk sands through three wells, the NS-08, the NS-15 and the NS-18.
Enhanced oil recovery history Originally, a blend of gas from Northstar and imported gas from the Prudhoe Bay field was used for enhanced oil recovery from the Ivishak. However, in 2005 injection switched from miscible injectant to injectant with a higher proportion of gas. Starting in 2010, when production from the Kuparuk sands began, gas from the Kuparuk was mixed with Prudhoe gas for injection into the Ivishak. However, following the termination of the gas supply from Prudhoe in 2014, just gas from the NS-08 well was used for the Ivishak injection.
But, with the addition of the NS-15 and NS-18 wells in 2016 and 2017 more Kuparuk gas became available for Ivishak production enhancement - increased gas production comes in particular from the NS-15 well, Hilcorp told the AOGCC. This has led to a restoration of pressure in the Ivishak reservoir to a level close to the reservoir’s original pressure, a phenomenon that has resulted in an improved proportion of oil to water production from the Ivishak.
Enough gas for Kuparuk injection Moreover, with there now being more than enough gas produced to support Ivishak production, there is adequate gas to begin injection into the Kuparuk, Hilcorp told the AOGCC. Injection would be achieved initially by converting the NS-18 well into an injection well. Further developments could include well recompletions, well workovers, well conversions for gas injection, and the expansion of Kuparuk enhanced oil recovery through the drilling or sidetracking of new wells, Hilcorp told the commission.
Total peak daily gas injection rates could go as high as 120 million cubic feet per day, with individual well injection rates anticipated to be some 50 million to 80 million cubic feet per day. However, rates will vary depending on the number of wells being used and the excess gas supply from the Ivishak reservoir, Hilcorp told the commission.
The Kuparuk reservoir at Northstar lies in the Kuparuk C and Kuparuk A sands, along the crest of a four-mile by two-mile, east-southeast to west-northwest trending, faulted anticline. Available data indicate that there is is an oil rim below a gas condensate cap in the Kuparuk A, while the Kuparuk C only holds gas condensate, Hilcorp told the commission.
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