MEXICO CITY — Output at Mexico's most important oil field has fallen steeply this year, raising fears that wells there that generate 60% of the country's petroleum are in the throes of a major decline.
Production at Cantarell, the world's second-largest oil complex, in the shallow gulf waters off the shore of Mexico's southern Campeche state, averaged just over 1.8 million barrels a day in May, according to the most recent government figures. That's a 7% drop from the first of the year and the lowest monthly output since July 2005, when Hurricane Emily forced the evacuation of thousands of oil workers from the region.
Though analysts have long forecast the withering of this mature field, a rapid demise would pose serious challenges for the world's No. 5 oil producer. The oil field has supplied the bulk of Mexico's oil riches for the last quarter of a century, and petroleum revenue funds more than a third of federal spending.
"Cantarell is going to fall a lot, and quickly," said independent consultant Guillermo Cruz Dominguez Vargas, a former executive with Mexico's state-owned oil monopoly, Petroleos Mexicanos, known as Pemex. "I can't imagine the strain on this society if there is nothing to replace it."
It would also be bad news for the United States, for which Mexico is the No. 2 petroleum supplier, behind Canada. And it could exacerbate tight global supplies that have kept oil at record prices.
The world's "elephantine" fields have already been bagged, forcing companies to hunt in ever-more-remote areas for smaller amounts of oil to feed burgeoning demand, according to Houston energy analyst William Herbert.
"Unfortunately, the era of low-hanging fruit ... has really run its course," said Herbert, co-head of research at Simmons & Co. International, a Houston-based energy investment bank. He put the odds of finding another field the size of Cantarell in Mexico or anywhere else at "slim and none."
Exceeded in size only by Saudi Arabia's leviathan Ghawar field, Cantarell is a prolific giant that is past its prime. Monthly production peaked in late 2004 at just over 2.1 million barrels a day and has fallen more than 15% since then. Experts agree it has nowhere to go but down.
The multibillion-dollar question is just how quickly Cantarell will lose its productive capacity, and whether Pemex will be able to coax more oil out of existing fields to take up the slack while it searches for new deposits.
Pemex did not respond to requests for an interview. But officials publicly have downplayed prospects of a swoon in the media and in official releases. In fact, the company has projected that its overall oil output will increase slightly in 2006 to an average of 3.4 million barrels a day from 3.3 million daily last year.
The firm has done extensive maintenance on Cantarell to keep the oil flowing. In a December 2005 news release, Pemex predicted that the field will produce an average of 1.9 million barrels a day in 2006, a modest 6% drop from 2005, followed by double-digit annual declines that would reduce average production to 1.4 million barrels daily in 2008.
Other studies aren't so optimistic. Seawater is threatening to swamp the wells of Cantarell as the field's pressure diminishes, a debilitating symptom of old age that makes it tougher to extract the remaining oil. Leaked internal reports of Pemex's own worst-case scenarios published in Mexican newspapers show production plummeting to about 520,000 barrels a day by the end of 2008 -- a 71% free-fall from May levels in less than three years.
Mexico City energy analyst David Shields said the swift drop over the first five months of 2006, and conversations with Pemex insiders have convinced him that prospects at Cantarell are worse than officials will admit publicly. June figures for the field won't be available until later this month. But Mexico's overall crude production fell in June, the third straight monthly decline, making it unlikely that Cantarell staged a revival.
"It's doing very badly," said Shields, general manager of Energia a Debate, an industry trade publication, and the author of two books on Pemex. "My reading of the situation is that it's dire."
Whether Cantarell's slide prompts changes in Mexico's oil sector remains to be seen. Critics have long lambasted state-owned Pemex as a hotbed of inefficiency and corruption that officials have treated more like an ATM than Latin America's largest company. But record oil prices have lessened the urgency to overhaul the company.
One would never suspect that trouble might be bubbling in Mexico's oil patch from the glut of petrodollars flooding its treasury. Federal officials last year siphoned $54 billion from Pemex to fund government spending that included a baseball stadium in Chihuahua and a gigantic flagpole in Nuevo Leon.
The trouble, analysts say, is that the government's take is so large that it has left little to reinvest in Pemex to keep the black gold flowing.