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Alaska Peninsula oil seeps investigated Division of Geological and Geophysical Surveys report looks at all proven Puale Bay-Becharof Lake-Wide Bay region seeps Alan Bailey Petroleum News Staff Writer
Alaska’s Division of Geological and Geophysical Surveys has published a report on all proven oil and gas seeps in the Puale Bay-Becharof Lake-Wide Bay region of the Alaska Peninsula. The report, prepared by Robert Blodgett and Karen Clautice, provides descriptions of seeps at 15 locations that are depicted on an accompanying map of the northeast end of the peninsula.
The report can be found at :
www.dggs.dnr.state.ak.us/pubs/pubs?reqtype=citation&ID=7189.
The descriptions of the seeps come from numerous research papers and the report provides a bibliography of published work on the seeps.
The authors of the report researched the original field maps and field notes of people who investigated the seeps. Oil industry field maps held by the U.S. Geological Survey and dating back as much as 100 years also provided useful information about the seep locations — the existence of the seeps provoked several oil rushes in the early 20th century.
According to the report all of the seeps occur in middle and upper Jurassic strata of the Kialagvik, Shelikof and Naknek formations. Evidence of active petroleum system The seeps seem to provide evidence of an active petroleum system under the Alaska Peninsula in what geologists term the Chignik subterrane — a suite of Mesozoic sedimentary rocks that extends north under the Cook Inlet basin.
A DGGS-led team has been investigating the seeps at Oil Creek, one of the better-known and most prolific seep locations, as part of a current geologic study of the Alaska Peninsula. Although the seeps occur in the middle Jurassic Shelikof formation, the team’s chemical analysis of oil samples from the seeps has shown hydrocarbon typing that in part matches the Triassic Kamishak source rock. Isotope analysis in the early 1990s had suggested co-sourcing from both the Kamishak and the middle Jurassic Kialagvik formation (equivalent to the source rock for oil in the Cook Inlet oil fields).
At an Alaska Geological Society meeting in January 2005 DGGS geologist Rocky Reifenstuhl described how over time, the flow of oil from the seeps has generated a 150-meter wide delta-shaped fan of tarry material.
“You can take your hand and stick it right in and it’s just like tar,” Reifenstuhl said. The team was also able to torch the gas emitting from the seep, despite the 30 mph wind that was blowing at the time, he said.
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