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Is Sunrise stalking something new? Marathon exploration well is shallower than a previous well in the region, suggesting a different target at the CI prospect Eric Lidji For Petroleum News
Marathon Oil Co. may be chasing something new at Sunrise.
Early completion data suggests the recent Cook Inlet exploration well is targeting a different prospect than the one encountered by a well drilled in the area 40 years ago.
Marathon drilled the Sunrise LK2 well about one mile west of the Sunrise Lake Unit No. 1 well, which Forest Oil drilled in 1970 to a depth of 14,500 feet. Forest encountered gas shows in the Tyonek formation below 11,000 feet, but not in commercial quantities.
In well logs at the time, Forest Oil reported a “small amount of gas” between 11,698 feet and 11,758 feet and some additional gas between 11,220 feet and 11,260 feet.
In a completion notice published by the Alaska Oil and Gas Conservation Commission the week of March 21, though, Marathon reported that it drilled Sunrise LK2 to a total depth of 9,918 feet and a total vertical depth of 9,798 feet, shallower than SLU No. 1.
Marathon drilled Sunrise LK2 relatively straight, angled slightly toward the northeast.
‘Zone of interest’ After completing the exploration well, located on Cook Inlet Region Inc. land in the Kenai National Wildlife Refuge east of the Swanson River field, Marathon said it “encountered a zone of interest” and was “continuing to evaluate the results to determine commerciality.”
The company also permitted a second well, Sunrise LK 2RD, with the same top hole location as Sunrise LK2, but a proposed bottom hole location just north of SLU No. 1.
Drilling reports suggest that Marathon is currently drilling a development well at the Ninilchik unit, rather than pursuing that second well location at the Sunrise prospect.
The company previously announced plans to drill three wells total this year.
Marathon has called Sunrise a “tight well.” In mid-January, the Peninsula Clarion quoted Carri Lockhart, production manager for Marathon in Alaska, as saying, “We probably won’t be saying a whole lot about it until we fully evaluate it, but cross your fingers.”
Discontinuous sands common Cook Inlet geology includes many laterally discontinuous sands, making it possible for one well to encounter a gas-bearing zone not encountered by another nearby well.
“While I do not know details of either well, it is possible that both wells encountered slightly different stratigraphy. In fact, given the fluvial depositional setting, I’d say there’s a fairly high probability of that,” said David LePain, chief of the Energy Resources Section of the Alaska Division of Geological and Geophysical Surveys.
In a December 2009 report, the Alaska Division of Oil and Gas included Sunrise among six potential onshore Cook Inlet prospects that “might yield between 40 and 120 (billion cubic feet) of recoverable gas” combined. It described Sunrise as a “lightly explored anticline trend.”
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