What a difference a day can make in the energy business. In one stroke, the future reserve and production schedule for China's CNOOC (NYSE:CEO) took a big step up.

That "stroke" was the announcement from Canadian energy company Husky Energy (TO: HSE) that it made a major natural gas strike in a deepwater field some 150 miles south of Hong Kong. If initial projections bear out upon further study, the find could total as much as 6 trillion cubic feet of natural gas, worth well in excess of $2 billion. Not only is this a big find in its own right, but it's also the first major deepwater find off the coast of China, and that's sure to encourage those who've been scouting out that area.

Of course, there are a lot of "if's" and "when's" involved in this story. First, the discovery needs to be further explored and characterized. And assuming that it lives up to initial promise, gas producers will need to develop the area -- drill wells, build production platforms and pipelines back to the shore, and so forth. Accordingly, I don't think you could really expect the production phase to begin before 2010. After all, companies like Transocean (NYSE:RIG) and McDermott's (NYSE:MDR) marine business are already pretty busy.

It's also important to note that CNOOC currently does not have a direct stake in this project. But it does have a "back in" right to assume a 51% interest in the project. Given the scale (CNOOC's gas reserves were 5.4T cubic feet at year-end) and potential value of the project, it's a pretty safe bet that it'll exercise that right.

Just to put the potential scope of this project in perspective, the high end of the guesstimate on this field's reserve potential would be almost triple Ultra Petroleum's (AMEX:UPL) total companywide proven reserves, and almost as large as those at Chesapeake Energy (NYSE:CHK). That's big.

In the meantime, CNOOC isn't a bad idea for investors looking to play on China's growing appetite for energy. By the same token, those who wish to invest closer to home might also want to consider Apache (NYSE:APA) or XTO (NYSE:XTO).

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Fool contributor Stephen Simpson but has no financial interest in any stocks mentioned (that means he's neither long nor short the shares).