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Identifying Alaska’s pot of gold
Kay Cashman Petroleum News
The Alliance’s theme for Meet Alaska 2006 — The end of the rainbow: Reaching Alaska’s elusive oil and gas pot of gold — begs the question: What’s left in Alaska’s hydrocarbon pot of riches?
Alaska north of the Brooks Range was covered in last week’s Petroleum News.
In southern Alaska, the Cook Inlet basin has been in production since before the start-up of the North Slope’s giant Prudhoe Bay field. Yet substantial aspects of Cook Inlet remain unexplored, partly due to industry attention being diverted to the North Slope with the discovery of Prudhoe, the largest oil field in North America.
The area has produced approximately 1.3 billion barrels of oil and 9 trillion cubic feet of gas since the late 1950s.
The U.S. Geological Survey’s 1995 assessment estimates undiscovered, technically recoverable oil resources of 0.19 billion to 0.97 billion barrels for the whole of southern Alaska. USGS also estimated 0.68-2.14 tcf of natural gas.
These estimates now seem conservative — a 2004 U.S. Department of Energy report on Southcentral Alaska gas said there might be as much as 10-14 tcf of undiscovered, conventionally recoverable gas in the Cook Inlet basin, plus 7 tcf of coalbed methane.
Sections of the southern Alaska basins lie within U.S. federal offshore and were not included in the USGS assessment. In 2000 MMS estimated 0.34-1.42 billion barrels of conventionally recoverable oil under lower Cook Inlet, with a mean (average) of 0.76 billion barrels.
The Susitna basin, a northern extension of Cook Inlet, remains largely unexplored. Bristol Bay barely explored The huge Bristol Bay basin shares many of the geological features of Cook Inlet but remains substantially unexplored — all but one of the 26 wells in the area have been drilled onshore at the edge of the basin.
A 1995 MMS assessment suggested the existence of up to 0.55 billion barrels of conventionally recoverable oil, with a mean of 0.23 billion barrels in the federal offshore. MMS estimated up to 16.03 tcf of natural gas (mean of 6.791 tcf).
The MMS 1995 assessment also contains estimates for the offshore areas of the Gulf of Alaska Shelf: 0.183-1.434 billion barrels of conventionally recoverable oil (mean of 0.630 billion barrels) with natural gas ranging from 0.937-10.589 tcf.
The Copper River basin north of Valdez contains similar geology to Cook Inlet and so offers some hydrocarbon potential. Interior and other basins Sedimentary basins in Interior Alaska include: the Holitna and Minchumina basins northwest of the Alaska Range; the Nenana basin near Fairbanks; the Yukon Flats basin, northeast of Fairbanks; and the Kandik basin on the Canadian border.
With the exception of Kandik, all of these basins share similar geological characteristics and probably contain gas.
The lower sections of the Yukon Flats basin may be more oil prone.
For central Alaska, the USGS 1995 assessment estimated up to 0.06 billion barrels of technically recoverable oil (mean of 0.32 billion barrels) and 0.51-7.31 tcf of conventional natural gas (mean of 2.76 tcf).
However, a 2004 USGS assessment estimated up to 600 million barrels of oil and up to almost 15 tcf of gas in just the Yukon Flats basin. (Mean values were 173 million barrels and 5.5 tcf.)
The gas-prone Norton Sound basin, offshore south of Nome, has many of the geological characteristics of the Interior basins. MMS estimated there may be up to 0.15 billion barrels of conventionally recoverable oil (mean of 0.05 billion barrels) and up to 8.74 tcf of recoverable gas (mean of 2.71 tcf).
The Navarin, St. George and St. Matthew-Hall basins on the Bering Sea outer continental shelf contain substantial thicknesses of Tertiary sediments and are all thought to be gas prone.
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