Speaking at the recent Reuters Global Investment Outlook Summit in New York, Lasry said the amount of distressed debt in energy had grown this year to between roughly $250 billion and $300 billion from $100 billion.

He said that offers opportunities for patient investors not bent on making a quick buck.

"Energy today is a once-in-a-lifetime opportunity," said Lasry. "Either you will get paid off, or you will become the new equity of these companies, but you need the luxury of time. You need to be able to wait two or three or four years."

Lasry oversees $13.2 billion at New York-based Avenue. He also became co-owner of the National Basketball Association's Milwaukee Bucks last year.

Avenue is among a handful of firms that have raised money in recent months for a dedicated energy fund.

Lasry closed the Avenue Energy Opportunities Fund LP in July after raising $1.3 billion, only to see the market become more distressed. Senior secured debt that was once available for 75 cents on the dollar now fetches 40 cents to 50 cents, he said.

"The whole market is oversold, and we're trying to take advantage," Lasry said.

He said the new fund has been investing 5 percent to 10 percent of its assets each month, biding its time as prices across the sector move further downward.

Lasry acknowledged that the fund lost money in its first few months but added that it has investor money locked up for roughly seven years so there is no hurry to sell.

For other investment firms, primarily mutual funds that must return investor capital on demand and hedge funds that promise to return it more quickly, recent heavy losses have become a problem, forcing some investors to resort to hasty selling at inopportune times, Lasry said.

The oil slump will hurt exploration and production companies, he said, but prices "will always come back. The question is, does it take six months or does it take three years?"

Lasry said Avenue was also raising money for a new fund that will invest in Europe with a focus on banks in Great Britain, Germany, Switzerland and Nordic countries.