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AOGCC approves new Meltwater rules ConocoPhillips allowed to drill new wells and sidetracks in North Slope field but must take precautions against future gas leaks ALAN BAILEY Petroleum News
In response to a request from ConocoPhillips, operator of the Meltwater oil field on the North Slope, the Alaska Oil and Gas Conservation Commission has issued a new area injection order for the field. A previous prohibition on the drilling of new wells has been removed from the injection order. However, the order specifies safety precautions for any new wells drilled from the surface, to mitigate the risk of hitting a shallow gas pool, given a previous history of the upwards leakage of injected gas from the field reservoir.
The field reservoir consists of discontinuous sand bodies in the Torok formation, a part of the Brookian sequence, the youngest of the petroleum bearing rock sequences on the North Slope. Within a couple of years of the field going into operation in 2001 ConocoPhillips found evidence that injectant, including natural gas, used for enhanced oil recovery, had been leaking from the reservoir rocks. And a subsequent investigation indicated that the material had leaked upwards through rock fractures into the strata above the reservoir. Since 2014 ConocoPhillips has injected natural gas rather than miscible injectant or water into the reservoir for enhanced oil recovery.
Pressure control ConocoPhillips remedied the leakage problem by limiting the injection pressures in the reservoir, a solution that stopped the injectant leakage at the cost of a reduced oil production rate. Modeling of the reservoir indicated that previous high pressure differentials between injection and production wells, leading to injectant leakage, could be attributed to poor fluid connectivity between the wells, with some injection wells being in different sand bodies from the production wells.
ConocoPhillips now wants to improve oil production rates without triggering more injectant leakages by repositioning well completions, to place injection wells in the same sand bodies as the production wells that the injectors are driving. The company anticipates achieving this objective by using coiled tubing drilling to drill sidetracks from existing well bores. However, the company has told the commission that it may have to also drill a new well from the surface to access one part of the field. Coiled tubing drilling involves the use of a continuous length of small-diameter, flexible drill pipe.
New drilling allowed The commission has now issued a new injection order, under which ConocoPhillips can now drill new wells and conduct well conversions in the field. However, any new well drilled from the surface must employ the same safety precautions as an exploration well, rather than a development well, given the risks associated with previously leaked gas, the commission says.
The commission is also allowing the injection of sea water or produced water from the Kuparuk River field for the purpose of surveillance or oilfield maintenance. And, with ConocoPhillips now having the previous injectant leakage under control, the commission is relaxing the field reporting frequency from monthly reporting to annual reporting.
However, the commission has not acceded to a ConocoPhillips request to eliminate having an expiry date for the area injection order - the injection order will expire after five years, unless ConocoPhillips requests an extension prior to the expiry date. The commission has been adopting a policy of putting sunset clauses into its orders, in recognition of the likelihood of changing circumstances for field operations.
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