Key terms in oil-supply debate

Here are some key terms in the oil-supply debate.

Peak oil

* Definition: The maximum volume of oil production achievable, after which output begins an irreversible decline. Sometimes called Hubbert's peak or the Hubbert curve for U.S. geophysicist Marion King Hubbert, who in 1956 theorized that oil production follows a bell-like curve and accurately predicted that U.S. oil production would top out between the late 1960s and early 1970s. Many subsequent peak oil predictions have missed the mark.

* Notable believers: Kenneth S. Deffeyes, author, former Shell geologist and retired Princeton professor; Colin J. Campbell, retired British geologist, author and founder of the Assn. for the Study of Peak Oil; T. Boone Pickens, oilman, hedge fund owner and alternative energy investor; Matthew Simmons, author and chairman of oil investment bank Simmons & Co. International.

Practical peak

* Definition: The belief that factors other than supply will impose a de facto cap on worldwide oil production. "Above-ground" limitations cited include instability in key producing nations, diverging priorities between producers and consuming nations, shortages of qualified workers and key exploration equipment, rising exploration costs and limited refining capacity.

* Notable believers: Tom Petrie, a vice chairman at Merrill Lynch & Co. Inc. and co-founder of energy investment-banking firm Petrie Parkman & Co. Executives at oil giants Total and BP. Others, such as consulting firm Cambridge Energy Research Associates, don't pinpoint a peak but believe that above-ground constraints are significant obstacles to future oil production.

Peak exports

* Definition: The notion that several of the world's key oil exporters are gaining economic strength and using more oil at home at a time when their overall production is peaking or in decline. Rising consumption and falling production in exporting nations could quickly erase available oil exports for the United States and others dependent on foreign supplies.

* Notable believers: Jeffrey J. Brown, independent petroleum geologist; Samuel Foucher, a signal processing expert. They created the Export Land Model to illustrate the problem, which is gaining currency in energy circles.

Peak demand