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First Reserve
First Reserve
CHC Helicopter Corp., part of First Reserve's portfolio, provides services to offshore oil and gas rigs.
2008 Rank: 10
2007 Rank: Not previously ranked
Recent buyout fundraising: $12 billion

Few firms dominate a niche the way energy specialist First Reserve does. Founded in 1983, the firm at one point owned 20% of all oilfield-services companies with a market cap over $1 billion. Unlike many PE firms whose deal flow has slowed, First Reserve's has been a gusher: Its deals represent a quarter of all LBOs by dollar volume this year, led by the two biggest deals of the year--one for an oilfield helicopter firm, the other for a British driller.

Headwind issue: First Reserve is starting to play in the alternative-energy space--historically a tough sector for private equity as investments are very sensitive to oil prices.

Worth noting: Founder Bill Macaulay is an avid bird watcher, and his wife is a leading ornithologist. Starting in Kenya in the early '80s, they have recorded over 2,600 bird calls.

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Last updated July 28 2008: 4:28 PM ET
Source: Rankings are based on a firm's most recently raised buyout fund(s). Fortune looked at data from Capital IQ, institutional investors, and the companies themselves to determine the size of the most recently raised buyout funds. For some firms that means a fund that was raised in 2007; for others it might be 2006. Whatever the date, the most recent fund was the one we counted. In the case of companies that raise multiple funds simultaneously as opposed to raising a single fund at a time, we chose to count only those private equity funds that were not raised in public markets and that were earmarked for buyouts (as opposed to investments in debt, venture capital, or other ventures).
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