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Could there be oil or natural gas under Alaska’s largest city? Anchorage: Don’t count on it Alan Bailey
People living in Anchorage, Alaska, may tend to think of oil and gas fields as distant from the urban environment of the city. Yet a glance at a geological map of Southcentral Alaska reveals that the city lies on the edge of the prolific Cook Inlet basin. With oil and gas fields not too far to the southwest, what are the chances of making a find right under the city?
Curiously, in 1921 geologist Alfred J. Brooks, after whom the Brooks Range was named, reported an oil seep “about a mile southwest of the town of Anchorage.” Brooks reported the oil from the seep as having a specific gravity of 0.880. Alaska geologist Robert Blodgett has investigated the location of the seep and thinks that it was in mud flats, under where Westchester Lagoon now lies, near the coast southwest of downtown — the lagoon was created a number of years ago by damming Chester Creek. Homestead land Another intriguing fact is that some land in the Anchorage bowl consists of homestead land, which means that some landowners own rights to the subsurface minerals. And in the past it has been possible to lease state subsurface under other parts of the city — in 1991 an Anchorage lawyer actually purchased a lease in state land beneath Jewel Lake.
But before rushing out to buy a lease or file a drilling permit application, you might want to look closely at the evidence for what is actually under the ground. Given that no one has seen the supposed oil seep again it seems likely that the seep was spurious, perhaps the result of a buried oil container. And five oil wells drilled onshore and offshore the Anchorage area have all failed to find even a trace of oil or gas.
The oldest recorded well in the city dates from 1921 and was located halfway between Chester Creek and Campbell Creek, about six miles east of Point Woronzof at township 13 north, range 3 west, section 23 of the Seward meridian. Now known as “Old Wildcat No. 1,” the well only reached a depth of 300 feet. The Alaska Oil and Gas Conservation Commission lists Anchorage Oil and Development Company as operator of the well, but the commission does not have any information about what the well found. Romig Park well In 1964 Pan American Petroleum Corp. (part of Amoco) drilled the Romig Park No. 1 well to a depth of 11,566 feet in full-fee private land in the Sand Lake area for Romig Park Inc. The well is located at township 12 north, range 4 west, section 10 of the Seward meridian. According to the well completion report the well encountered porous zones in Tertiary sandstone at between 1,570 feet and 2,140 feet, and in sandstone of the Cretaceous Matanuska formation between 11,535 feet and 11,543 feet.
Yukon Service Inc. drilled the Campbell Point No. 1 well in 1968 near the coast north of the mouth of Campbell Creek at township 13 north, range 4 west, section 31 of the Seward meridian. That well drilled through 3,910 feet of Tertiary strata before penetrating volcanic rocks. The well bottomed in Cretaceous sedimentary rock at 4,315 feet.
Offshore Anchorage, the Fire Island No. 1 well north of the Kenai Peninsula drilled in 1984 by ARCO achieved a depth of 14,237 feet, with Tertiary sediments to at least 11,508 feet according to the completion report. The well location is township 12 north, range 6 west, section 29 of the Seward meridian. The Turnagain Unit No. 1 well, in the middle of Turnagain Arm offshore the mouth of Campbell Creek, was drilled to a depth of 6,325 feet by Pan American Petroleum in 1967. The well location is township 11 north, range 5 west, section 9 of the Seward meridian and the completion report noted Tertiary sediments at 1,240 feet and Cretaceous sediments at 3,870 feet. Relatively thin Tertiary Veteran Alaska geologist Arlen Ehm has interpreted the logs from the wells in the Anchorage area. Ehm has told Petroleum News that he has determined Tertiary strata down to about 3,900 feet in the Campbell Point well and down to about 2,000 feet in the Romig Park well. Both wells have Cretaceous strata below the Tertiary. The depths of the Tertiary support a concept that Anchorage lies on a shelf at the edge of the Cook Inlet basin, with the Tertiary sequence thinning towards the metamorphic rocks of the Chugach Mountains.
Ehm has determined a thick Tertiary sequence down to about 13,900 feet in the Fire Island well, indicating that this well is inside the main Cook Inlet basin.
So what does all this mean in terms of oil and gas potential under Anchorage?
The relatively thin Tertiary sequence found in three wells coupled with the total lack of oil and gas is not encouraging. And little seems to be known about the geological structure under Anchorage. But Ehm thinks that there’s Tyonek formation, a good gas reservoir, under the city. And there do appear to be Mesozoic rocks of a sequence that may include the oil source rocks of the Cook Inlet.
But, nowadays, would anybody want to try to drill within the city?
Editor’s note: Petroleum News would like to thank Robert Blodgett, Arlen Ehm, Tom Marshall, Brit Lively, Dan Donkel and Bill Vallee for contributing information for this story.
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