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Conoco applies for Narwhal water pilot
Kristen Nelson Petroleum News
The Alaska Oil and Gas Conservation Commission has tentatively scheduled a public hearing on an application by ConocoPhillips Alaska for a pilot water project at the Narwhal reservoir in the Colville River unit.
The hearing is tentatively set for 10 a.m. Oct. 29, but if no request for a hearing is timely filed the commission may consider issuance of an order without a hearing.
ConocoPhillips is requesting authorization for water injection into the Narwhal reservoir through a waterflood pattern pilot.
The company said this is considered a pilot project because feasibility of injecting water into the Narwhal reservoir has not been established. “This pilot project will aid in determining the commercial viability of developing Narwhal as an enhanced oil recovery project,” the company said.
A three year pilot is being requested to allow time to drill the first injector, test injection performance, analyze results, drill the second injector, test injection performance and observe and analyze results.
CD4-595 The CD4-595 exploration well was drilled within the Colville River unit in June, ConocoPhillips said, “to understand the ability to drill, complete, and produce the Narwhal horizon.”
The first offset injector will be drilled in October, with injection planned to begin in January, and drilling of the second injector contingent on results from the first.
ConocoPhillips said Narwhal is expected to be developed as a line drive water alternating gas flood with horizontal producers and injectors. “The pilot results will inform whether this development concept is optimal.”
Application would be made to AOGCC for pool rules and an area injection order if commercial viability of the discovery is established and the development is sanctioned for development, the company said.
Two injectors The pilot project would occur at the CD4 drill site. Two offset injectors would be drilled in the pilot project, the first, CD4-594, some 1,000 to 3,000 feet east of the CD4-595 well. “The optimum pattern spacing for WAG development in this reservoir is still under analysis,” Conoco said. The first injection well “will allow interference and injection testing of the Narwhal reservoir to help establish the optimal pattern spacing and justify commerciality of the reservoir.”
Drilling of the second injector would be determined by outcome of the first injection well and testing. The second well would “continue a long-term injection and production test with a fully supported producer pattern centered around CD4-595.
The Narwhal reservoir is defined by the Qugruk 3 well with true vertical depth subsea limits of 4,068 to 4,971 feet with a measured depth of 4,192 to 5,152 feet.
“The Late Cretaceous Narwhal sandstone represents a north-south elongate, eastward prograding deltaic marine sand. The Nanushuk Group is broadly age equivalent to the Narwhal sands,” the company said in its application to the commission.
“The Narwhal sands in the CRU represent a Brookian topset play in which thick deltaic marine sands (up to 800 ft gross sand) are trapped stratigraphically,” ConocoPhillips said. The Narwhal extends for some 35 miles over the length of the field; it has been penetrated by some four wells in the CRU and more than 10 wells in the vicinity of the Colville River and Pikka units.
Conoco said that based on data from exploration wells the reservoir is slightly undersaturated with an initial pressure of some 1,920 psi.
“This does not leave much driving force for primary depletion,” Conoco said, and estimated that recovery without injection would be less than 5% but could be upwards of 30% with waterflood based on reservoir modeling and analog data.
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