Energy investors are smiling. Crude prices are skyrocketing, energy companies are enjoying record earnings, and share prices are climbing. But those smiles may be gone soon. Big oil profits may not last. Record energy prices have diverted attention from the oil industry's dirty little secret: Production is falling and reserves are on the decline. Rather than address the problem, most oil companies are sinking their money into share buybacks and dividends to boost their stock prices. Without new investment, companies run the risk of not having enough oil to sustain record profits and may hasten a far worse energy crisis. The country's national security, based largely around cheap and plentiful oil, could be put at further risk if oil becomes scarce and prices rise. "From a national security standpoint, they'd be better served to continue drilling," says James Williams, an energy analyst at WTRG Economics in London, Ark. Oil prices have doubled over the past two years, driven by growing demand from recovering American and Asian economies and lower supply levels caused by hurricanes, rebel attacks and wars. On Wednesday, oil closed at $62 on the New York Mercantile Exchange. At the country's largest energy companies, revenue has soared thanks to high oil prices. Exxon Mobil ( XOM), the world's largest oil company, reported record earnings of $36.1 billion -- the highest for any American public company last year -- and beat its previous record of $25.3 billion in 2004. Earnings at the four other supermajors were just as stellar. Net income climbed 37% at Shell ( RDS.A), 31% at BP ( BP), 13% at Total ( TOT) and 6% at Chevron ( CVX). "The surge in oil prices took companies by surprise," says Fadel Gheit, an oil analyst at Oppenheimer & Co. in New York. "They didn't expect the windfall profits and were ill prepared to handle the instant wealth. It's like winning the lottery."