Before long, you may not be able to tell the cast of characters in OPEC without a playbill. With Angola and Ecuador having recently joined the crew -- in the latter's case, it was actually a second membership -- Indonesia is now exiting stage left.

The newly announced departure is the result of a combination of increasing oil prices and the country's status as a net crude importer. Nevertheless, even though the break had been rumored, it's still something of a surprise to see the archipelago -- which began producing oil with the aid of what's now Royal Dutch Shell (NYSE:RDS-A) (NYSE:RDS-B) in the late 18th century -- file for separation.

Indonesia produces about 927,000 barrels of crude every day, down from 950,000 daily barrels in 2007. But its demand now sits in the range of 1.2 million to 1.3 million barrels per day. Therefore, like other net importers, and as Energy Minister Prunomo Yusglantoro noted in announcing his country's resignation from the cartel, Indonesia is "not happy with high oil prices." Ah, yes: It depends upon whose ox is being gored.

I expect some fluidity (no pun intended) from OPEC in the years ahead. As noted, Angola, Africa's second-largest producer, joined up last year. And Ecuador, with production slightly greater than 500,000 daily barrels -- or just more than half of Texas' output -- re-upped in 2007 as well.

That's not to say we'll soon read about Lone Star State representatives donning burnooses and winging off for meetings in Vienna. But I wonder about Brazil, where national oil company Petrobras (NYSE:PBR) is making discoveries more rapidly than tots at an Easter-egg hunt.

And then there's Kazakhstan. When not battling with the big oil companies -- like Chevron (NYSE:CVX), ExxonMobil (NYSE:XOM), and Italy's Eni (NYSE:E), which are attempting to develop its big fields -- its leaders must be imagining the energy bucks that'll soon begin flowing in. While I think the prospect that Kazakhstan could become a card-carrying member of OPEC is remote, I've learned not to rule anything out.

What's the meaning of all of this for Foolish investors? To answer, I'll simply invoke Indonesia, where receding production is being blamed on tiring of wells and insufficient investment. It's therefore something of a microcosm for much of the producing world.

As such, and with the U.S. Energy Department's Energy Information Administration having noted this week that the world's oil exporters simply can't keep up with growing demand, this is probably an excellent time to re-oil your portfolios.

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