My early 2009 investment advice is rather simple, but could also turn out to be profitable for you: Don't assume that the second half of this year indicates that the energy markets will be languishing next year. Unless you want to miss out, you have to stay tuned to this temporarily down-in-the-dumps sector.

Indeed, as I write this, several situations have unfolded or are about to do so that could affect oil and gas supply, demand, and prices for many years. First of all, the ink is now about dry on a new agreement between Royal Dutch Shell (NYSE:RDS-A) and PetroChina (NYSE:PTR). Under the pact, which links Europe's biggest Big Oil member with the largest energy company in China, PetroChina will buy up to 40 million tons of liquefied natural gas (LNG) from Shell over a 20-year period.

It appears that much of that gas will come from the Gorgon project, off the shores of western Australia. The Gorgon fields are operated by Chevron (NYSE:CVX), in partnership with Shell and ExxonMobil (NYSE:XOM). The LNG agreement comes just as Abu Dhabi committed to contributing $1.1 billion toward an LNG project in Papua New Guinea. The deal is expected to provide the funds for the latter country to invest in Australian oil company Oil Search.

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On top of that, there are cartel activities that could affect oil and gas prices significantly. Obviously, tomorrow's OPEC meeting in Cairo will have an impact, because some OPEC members and their new friends -- read Venezuela, Iran, and Russia -- are hoping that the group will strive to continue cutting production until global crude prices are pushed back up to the $80 to $100 range.

But the Organization of Petroleum Exporting Countries may not be the only cartel game in town for long. Iran, Qatar, and Russia have recently been brainstorming about the formation of a "gas OPEC." I find special -- and somewhat daunting -- significance in that possibility, if only because of Russia's role as gas supplier to much of Europe.

So stay tuned, Fools. I'm convinced that 2009 could be a far more active year for energy than is generally assumed. And with crude prices likely at or nearing a bottom, I'd pay especially close attention to the members of Big Oil. My two favorites these days are ExxonMobil and BP (NYSE:BP).

Exxon's wearing four stars in the Motley Fool CAPS parade today, while BP has five. Have you cast an opinion on either of these Big Oil players?

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Fool contributor David Lee Smith doesn't own shares in any of the companies mentioned above. He does, however, welcome your questions, comments, or kibitzing. The Fool has a disclosure policy that doesn't contain a bit of gas.