Matthew Simmons says the world’s fuel tank may be closer to empty than most people know, or will acknowledge. If he’s right, we may in the not-too-distant future look back on the days of $3-per-gallon gasoline with nostalgia.

Simmons, who will speak in Spokane next month, in May published “Twilight in the Desert,” which suggests oil reserves in Saudi Arabia are much less than most estimates. And if the vast Saudi fields are past their prime, he says, not only will they not be able to help slake the oil thirst of a China or India, they may not be able to sustain the output so vital to the U.S. economy.

In fact, he says, the U.S. may be making the situation worse by pressing the Saudis to increase production in ways that will compromise their capacity to pump more oil in the future.

“Trying to cajole them into producing more oil is dangerous,” says Simmons, who wrote “Twilight” after analyzing more than 200 technical papers on Saudi Arabia’s oilfields, and visiting the Middle East kingdom. The Saudis maintain pressure in the underground formations that hold the oil by injecting water, a common practice in the industry. Done improperly, the pressure eventually collapses, and with it the field’s productivity. In the meantime oil continues to flow and reserves appear to be healthier than they really are.

Despite the pumping of 60 billion barrels of oil since 1979, Simmons says, estimates of reserves never seemed to change. Saudi Arabia, Iran and Iraq were content to keep pumping, reassured by the U.S. that their reserves were all but inexhaustible. And their willingness to pump was driven as well by the collapse of oil prices to around $10 per barrel, which cut revenues they had come to rely on.

There has been a collective denial about the capacity of oilfields that, some of them, have been in production for more than 50 years.

“We just don’t want to believe they are too old,” he says.

Simmons says he has been surprised his conclusions did not attract more criticism. Although the Saudis and some oilmen pooh-poohed an analysis based mostly on an interpretation of technical tracts, many others accepted his conclusions. Also, as he promoted “Twilight” on talk radio, he was pleased by the thoughtfulness of listeners and hosts who already seemed attuned to his message. Their frequent question: “What do we do now?”

At the top of his list is a survey of what untapped reserves might remain in the U.S., especially in the offshore waters now out of bounds to exploration — including most of the West Coast — and Alaska.

“We have to do ANWR,” he says, referring to the controversial Alaska National Wildlife Refuge.

Katrina has shown the folly of relying on Gulf of Mexico oil and gas reserves subject to periodic interruption by hurricanes, he says.

Simmons admits to some unfamiliarity with some of the non-traditional ways of producing fuels, but dismisses corn-based ethanol for its inefficiency. About the only good that can be said of the recently enacted Energy bill, he adds, is that the legislation satisfied the congressional hunger for pork. Now, the nation can get down to addressing its real energy problems.

His priority is transportation sector oil consumption, 70 percent of the nation’s total. That share should be lowered not by imposing automotive mileage requirements, Simmons says, but by moving more freight by railroad and barge. Rail can be as much as 10 times more efficient than trucks, and barging could achieve an even bigger increment of savings compared with railroads. He’s also an enthusiast of car pools, and working from home.

Simmons predicts high transportation costs will eventually repatriate some of the manufacturing activity that has moved overseas. Even truck farms, which once supplied much of the produce consumed in urban areas, could supplant industrial farms in the U.S. and overseas that grow tomatoes or what-have-you at the end of very fuel-consumptive supply lines.

Sounds like back-to-the-land kind of talk, yet Simmons is an investment banker who has catered to Houston’s energy community for more than 30 years.

But Simmons adds that he is working on an op-ed newspaper piece with former Arizona congressman and noted environmentalist Stewart Udall. The working title: “50 Years of Energy Mistakes Have Finally Caught Up with Us.”

Recommended subtitle: “Twilight on the Interstate.”

Simmons will keynote an Oct. 4-5 conference here entitled “Global Oil Depletion and Implications for the Pacific Northwest.” Other eminent speakers are also on the agenda. You can register on-line at https://capps,wsu.edu/globaloil/, or by calling either 1-800-942-4978 or 1-509-335-4194.

Spokane seldom gets this kind of high-level perspective on what may be the biggest challenge facing the nation.