“Syriana”Warner Brothers PicturesWritten and directed by Stephen GaghanStarring: George Clooney, Matt Damon, Jeffrey Wright, Chris Cooper, Alexander Siddig and Tim Blake NelsonRated R/126 minAvailable on DVD June 20Three-and-a-half out of four stars

I’ve seen it twice now, and it’s hardly more comprehensible the second time around-and I could hardly care.

In Stephen Gaghan’s “Syriana,” a grim and thrilling mosaic of corruption, that dry sucking sound you hear-but don’t hear-is a straw, thrust into our planet, thirsting for oil that’s almost gone.

The world’s dependency on this most precious natural resource brings out the worst in those who don’t see in terms of living and dying, but in terms of winning and losing.

“Syriana” is a deeply pessimistic film that’s all the more terrifying because it’s probably true.

Gaghan, who wrote the Oscar-winning script for “Traffic,” does similar work here, patch-quilting a story of characters who sometimes poke our emotions, but mostly represent rungs on a ladder. A worldwide net is thrown, capturing everyone from disposable immigrant employees to demoralized government agents, so it’s inevitable that some of these characters are types rather than full-blooded human beings.

It’s a slightly frigid approach-like cogs in a machine-but perhaps that is Gaghan’s point. Every one of his characters plays an integral part in a machine that perpetuates corruption, violence and heartbreak, all for the claim of diminishing oil supplies.

Bob Barnes, a grizzled CIA agent, is certainly a cog, whether he knows it or not. George Clooney (who won an Oscar for his role) plays Bob, a yes-man tired of saying yes. He’s been asked to arrange the assassination of Prince Nasi Al-Subaai (Alexander Siddig). The details of why are murky-even to Bob-but they may have something to do with the prince’s radical ideas concerning the king’s oil empire.

Matt Damon plays Bryan Woodman, chief financial adviser to the Al-Subaais. He lives in Geneva, Switzerland, with his wife (Amanda Peet) and their two young children. Bryan is a decent, pragmatic man, but not above exploiting a family tragedy to boost his career.

In Washington, D.C., lawyer Bennett Holiday (Jeffrey Wright) investigates the shady circumstances surrounding a merge between Connox and Killin, two powerful oil companies. When he’s not sifting through evidence of bribery and back-stabbing, he’s pouring coffee for his alcoholic father.

Scads of other characters gather around the fringes, but any further explanation would require a chart with more branches than a pine tree. Gaghan’s script is deliberately disorienting, running us and its characters through a labyrinth with nothing but dead ends.

Hope is offered in the final moments, but it’s a hollow hope. If we are to believe the things “Syriana” shows and tells us, the dispute over oil-and the extremes some people will go to “win,” as they say-will only get worse.

“Syriana” is the kind of movie that demands your constant attention. It’s taxing, yes, but ultimately worth it.