NEW YORK (CNN/Money) - Hurricane Katrina wreaked havoc on New Orleans, but it sent some investment portfolios sky high.

Trend-following hedge funds, which trade systematically based on mathematical models, profited handsomely from the spike in oil. Many of these funds had long positions in oil – meaning they were betting prices would continue to rise – before Hurricane Katrina touched down in Louisiana.

Post-hurricane, crude oil prices shot up about $3 a barrel – or $3,000 per futures contract. While the NYMEX exchange limits funds to 20,000 contracts, most funds hold between 5,000 to 10,000, according to traders. A fund with 10,000 contracts would have netted a cool $15 million from the $3 spike.

The hurricane, which has killed at least 120 people according to the latest estimates, hit Louisiana on Monday. Estimates of the insured losses vary widely, but risk modeling firm Equecat estimated the damages at between $9 billion and $16 billion.

The hurricane damaged refineries, meaning that even if the oil could be imported, it couldn't be refined.

Katrina forced the closure of more than a tenth of the United States' refining capacity and a quarter of its crude oil output, spurring a spike in gasoline and heating oil prices, according to a Reuters report. Over 1.4 million barrels per day of crude production, or about seven percent of domestic demand, were still shut the day after Katrina tore through the Gulf, the report said.

"It hit in the very heart of the oil and gas industry," said Salem Abraham, founder of Abraham Trading Co., a systematic trend follower.

"Most systematic traders are trend followers so I'm sure most of them would have been long (oil)," said Abraham, whose fund had a long position in oil before the hurricane hit.

"For our firm, it's been a very good month – natural gas was our most profitable trade, followed by unleaded, heating oil, and then crude oil," said Brian Proctor, a trading veteran who is now vice president of marketing for ECM Capital, a trend-following firm in Chicago.

Proctor put his firm's gains in perspective, saying, "It's hard to be real excited about it – it's a tough thing to be living through," adding that he just returned from New Orleans himself, driving his daughter home from Tulane University, where she was supposed to start college this fall.

Said Rajpal Arulpragasam, president and CEO of Archetype Risk Advisors, a New Haven, Conn.-based quantitative investment firm, "Most hedge funds were probably positioned OK going into it by luck because the market was already trending up," he said. "The markets behaved pretty sanely – though it may not feel like it when gas goes up 18 cents overnight."

But traders say those gains, while substantial, may have been offset by losses in other commodities. Trend followers who had been short cotton and grains, posted losses when those commodities went up after the hurricane. Some traders think that may have been a knee-jerk reaction by the market, however.