By Matt Daily

NEW YORK (Reuters) - Chevron Corp <CVX.N> said on Wednesday that its board had approved share buybacks of up to $15 billion over the next three years, the latest in a series of huge repurchases by oil companies.

Chevron said its new repurchase program was equal to the three $5 billion buybacks that were completed in 2005, 2006 and 2007.

Oil companies have been buying up massive amounts of their own stock on the market to pass on the windfall profits from soaring energy prices in recent years.

Chevron's buyback matches the $15 billion program that peer ConocoPhillips <COP.N> announced in July. ConocoPhillips plans to complete those purchases by the end of 2008.

Crude oil prices reached a record high of $83.90 per barrel on Thursday, fueled by the U.S. interest rate cuts, the weakening dollar and fears of supply disruptions from storms in the Gulf of Mexico.

"Our continuing strong cash flows have enabled us to fund a significant capital program budgeted at almost $20 billion in 2007, increase dividends to our stockholders, repurchase our shares in the market and reduce the company's debt," Chevron Chief Executive Dave O'Reilly said in a statement.

The second quarter was the largest ever in the history of U.S. companies' buybacks, with the Standard and Poor's 500 members spending $158 billion on their own stock, according to S&P analyst Howard Silverblatt.

During that quarter, buybacks outpaced capital expenditures, he said.

Chevron has been buying about $1.1 billion of its shares from the market per quarter, well below industry leader Exxon Mobil's <XOM.N> top mark of $9.2 billion in the fourth quarter of 2006.

S&P 500 companies began the buybacks in earnest in the fourth quarter of 2004, Silverblatt said, with about $1.1 billion in shares being returned to corporate treasuries since then.

The technology sector has been the most active, claiming about 23 percent of all the buybacks, followed by the financial sector at nearly 22 percent. The energy industry had contributed about 9.7 percent of the S&P's buybacks in that time.

Chevron shares were up 1.2 percent at $93.02 in morning New York Stock Exchange trade, just ahead of the 1 percent gain for the Chicago Board Options Exchange's oil index <.OIX>.

(Reporting by Matt Daily)