What made Benjamin Graham the investor that he was? For him, the intelligent investor was a realist who sold to optimists and bought from pessimists. That opportunity beckons us now!

The market tanked once again on Thursday and Friday. And not surprisingly, the oil and gas industry saw a massive sell-off. But as Foolish colleague Morgan Housel noted, the best returns are made during the darkest days. There does not seem to be any reason to disagree. And of course, this is where I'm sniffing opportunity.

Companies operating in the exploration and production space saw some of the biggest hits. Fears of another recession caused crude prices to plunge, taking these stocks along with them. Still, this is not entirely surprising with investor emotion running pretty high for the last two weeks. But this is where Fools should capitalize.

Should we worry?
Yet, is there anything fundamentally wrong with these companies? I don't think so. In fact, while oil prices have seen a drop, production has been increasing steadily. And why is that? Because the companies know for sure that they will sell whatever they drill. The perfect example here is Anadarko Petroleum, which fell 8%. Record production levels have seen the company register substantial growth in the last quarter. In other words, it's simple economics here. Demand for oil and gas has been growing by the day and it will keep growing.

The promising stars
The shale play operators have all seen a massive drop in share prices. Companies operating in the Bakken shale have been the worst hit. Continental Resources (NYSE: CLR) saw a fantastic fall by 10%, followed by Brigham Exploration (Nasdaq: BEXP) by 9.5% and Kodiak Oil & Gas (NYSE: KOG) by 8.3%. And these are the three stocks whose long-term outlook has been extremely positive.

Kodiak has been very strong in terms of production, which has translated into phenomenal earnings growth. A fall in price realizations should not be a major hindrance for this company. And the same holds for Continental and Brigham. The former, being one of the major players in the region, has seen almost 25% shaved off from its share price in the last three weeks.

The Eagle Ford players have witnessed another substantial sell-off. EOG Resources (NYSE: EOG), El Paso (NYSE: EP), and Pioneer Natural Resources (NYSE: PXD) have each seen a drop of more than 6%. And this is precisely at a time when the shale play has witnessed marked progress in production and development of its reserves. With El Paso going for a spinoff of its E&P arm, and a proposed dividend of $0.60/share next year, things haven't looked more exciting.

The value investor will see the long-term prospects of these companies. This might sound strange to those relying on trading algorithms. But that's why Fools stand out.

Natural gas is another commodity that many wouldn't want to own because of its current bearish outlook. But the long-term promise that it holds has not waned. One of the most interesting companies in this business -- Ultra Petroleum (NYSE: UPL) -- saw a drop by more than 7%. The stock's long-term outlook brings the perfect opportunity now for the patient investor's portfolio.

Foolish bottom line
The fundamental investor should see opportunity from this crash without much reason to panic. In fact, the common mistake of going with the tide is what Fools should be wary of. Wall Street Journal columnist Jason Zweig put it simply, "The intelligent investor dreads a bull market, since it makes stocks more costly to buy." However, these wild days have created an opportunity that does not come about very often.

What do you think about the prospects of these energy companies? Write your comments below.