Moreover, those first 1 trillion barrels were among the easiest to reach. The days of easy gushers and overnight millionaires are long gone. Now the going gets harder.
Where underground formations are highly favorable, as in the Gulf of Mexico and Saudi Arabia, oil drillers can often retrieve 60 percent of the oil. But in marginal formations such as some found in Oklahoma, the average rate of recovery can be as low as 8 to 10 percent. Worldwide, the average is about 35 to 40 percent, according to the US Energy Information Administration.
In short, only 2 trillion to 3 trillion barrels may remain for our use.
Even more worrisome is the demand equation. It took 146 years for the world to use the first 1 trillion barrels. The next 1 trillion barrels will be gone by around 2030. After that, we could have as little as 1 trillion or 2 trillion barrels of conventional oil left.
Some experts who follow these issues closely are getting worried. One big change, particularly in the past two years, has been increasing international competition for oil supplies.
During most of the past century, it was mainly the United States, Japan, and Europe that vied for the world's petroleum supplies. Now other nations like China and India are developing their own needs for oil to fuel their factories and their rapidly expanding fleets of automobiles, trucks, and airplanes. That could set off a scramble for worldwide oil reserves, and it seems to assure that higher prices - at least higher than we are accustomed to - are here to stay.