Q. How much reserves are in the north slope?
- Bob Hurwitz, Hartford, Conn.
A. The short answer: about 35 to 36 billion barrels of crude oil and 137 trillion cubic feet of natural gas.
That compares with the 236 million barrels of crude oil Alaska produced in 2009, 96 percent of it from the North Slope. Alaska is second only to Texas in oil production.
But before we go any further, let's explain what crude oil reserves are. The most succinct description we found is at oilprices.org.
All the oil in an oil field is referred to as "oil in place." "Reserves" are considered the portion of that oil that's commercially recoverable through the latest technology.
Reserves are further classified into two major categories: "proved" and "unproved" reserves.
Proved or proven reserves are recoverable under prevailing political and economic conditions using current technology. They are 90 percent certain to be qualified as gettable.
Unproved reserves can be divided again, into categories such as probable and possible.
Next, let's explain the Alaska North Slope.
Like it sounds, the area slopes down toward the sea in a northerly direction starting along a mountainous region known as the Brooks Range.
The North Slope consists of five subdivisions: the Alaska National Wildlife Refuge; the Central Arctic area between the Colville and Canning rivers; the National Petroleum Reserve Alaska; the Beaufort Sea Outer Continental Shelf; and the Chukchi Sea Outer Continental Shelf.
By the end of 2007, Alaska North Slope oil fields had produced 15.7 billion barrels of oil, or about 72 percent of what's available from currently developed fields.
An estimated 6.1 billion barrels is still recoverable from these same fields, according the National Energy Technology Laboratory of the Department of Energy.
Here's the NETL's take on total North Slope reserves, from an April 2009 report: "the forecasts of economically recoverable oil ... including reserves growth in known fields, is 35 to 36 billion barrels."
Here are factors that would reduce that number, some of which are likely to transpire, the NETL says.
• If the environmentally sensitive ANWR area is removed from consideration, the estimate is reduced 6 billion to 7 billion barrels.
• Removal of ANWR and the Chukchi Sea area together cuts the estimate by 16 billion to 17 billion barrels.
• Removal of ANWR, Chukchi Sea and Beaufort Sea areas cuts the estimate by 20 billion to 21 billion barrels.
Issues that could bring about these reductions, NETL says, are land access; cleanup requirements; protection of bowhead whales and other species; and water and gravel availability for building ice roads, exploration pads and other infrastructure.
- Dennis Joyce
Submit your question here or visit our Gas Prices page and retail writer Richard Mullins will get you the answer.