New find may add to Mexico's biggest oil field-Pemex

MEXICO CITY, May 20 (Reuters) - An exploration well drilled near the offshore Ku Maloob Zaap heavy oil field, Mexico's most prolific producer, appears to show reserves at the complex that could be more than previously thought, the head of Mexico's state oil company said on Wednesday.

The Tekel-1 well, drilled 6 kilometers away from another well known as Ayatsil, flowed at 6,000 barrels per day when completed in February.

"This well alone brought 100 million barrels of oil equivalent of new reserves and confirmed the extension of the Ayatsil field," Pemex Chief Executive Jesus Reyes Heroles told reporters.

Pemex geologists are planning to drill two more wells nearby later this year to better delineate the Ayatsil field, Reyes Heroles said.

The reserve estimate has not yet been certified by third parties and Pemex is not including the well in its current reserve estimates.

Ayatsil, found last year, is expected to help extend the life of Ku Maloob Zaap, which overtook the Cantarell field as Mexico's most productive oil field this spring.

Pemex has been struggling to replace output lost at Cantarell due to natural declines amid a dearth of major new discoveries.

Ku Maloob Zaap is expected to reach peak production this year at around 820,000 barrels per day before starting to slowly decline in 2010.

The Ayatsil field is expected to slow the decline of Ku Maloob Zaap, giving Pemex a bit more breathing room to find more oil in the deeper waters of the Gulf of Mexico.