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Analysis

Cantarell: Rise and Fall of Mexico's Greatest Oil Field

Wed, 01/25/2012 - 10:07

The discovery of Cantarell was one of the most important moments in the history of Mexico’s oil and gas industry. Located 105km offshore in the Bay of Campeche, it was discovered with the help of Rudesindo Cantarell, a local fisherman who in 1976 complained to the local authorities about oil in the bay clogging his nets. When Pemex went to investigate the source of the oil, they discovered the largest field found to date in Mexican territory, the country’s only supergiant discovery.

When the field was developed in the 1980s, it was the world’s largest offshore development project; total installation costs reached more than US$5 billion. Pemex began production at Cantarell in 1979 and by 1981 the complex was producing 1.16 million bbl/day. Oil production at the Cantarell complex represented 36.7% of the country’s total production in the 80s, 40.8% in the 90s, and 56.8% from 2000 to 2007.

The geology of the Cantarell field was formed by the asteroid impact responsible for the Chicxulub crater, and is formed from carbonate breccia from the Upper Cretaceous period. From Cantarell, crude is transported  through pipelines to storage tanks on land at Dos Bocas and offshore tankers at Cayo de Arcas.

The complex comprises several small fields and four main ones: Akal, Nohoch, Chac and Kutz. Akal is the largest of the four, accounting for 91.4% of Cantarell’s original oil in place.

Since the Cantarell field first started production, it has been Pemex’s most important producing asset, accounting for 63% of Mexico’s crude oil production in 2004. That year marked the field’s peak output of 2.14 million bbl/day and it was around the same time when the country’s global production rates reached the highest level in history. Since 1979, the year in which Cantarell first saw production, Mexico has produced nearly 30 billion barrels of oil. Of these, approximately 13 billion barrels have been extracted from the Cantarell complex.

Even before Cantarell reached its peak, Pemex was fighting to maintain production at the field. For the first 20 years of its life, Cantarell had a large natural gas bubble in the reservoir that maintained high pressure and accounted for its impressive production rate. Once this pressure started to dissipate at the end of the 1990s, production rates dropped dramatically to under 1 million bbl/day. In order to counteract this, Pemex launched a nitrogen injection project to boost Cantarell’s reservoir pressure, which was largely successful. By 2002 production had increased to 1.9 million bbl/day. At this moment, Cantarell was the second highest producing field in the world after Saudi Arabia’s Gwahar field.

After Cantarell reached its natural peak in 2004, the field declined extremely quickly. In 2006, Pemex announced that production fell by 13.1%, with a 15% drop predicted for 2007. In May 2008, production fell a further 33% to 1.07 million bbl/ day. By 2011, output was estimated only at 449,000 bbl/day.

It was clear that if Pemex wished to preserve Cantarell’s production level, and therefore its revenues, the NOC would have to come up with a plan to stem the bleeding at Cantarell. In 2008, Pemex invested US$2.88 billion in a rescue plan for Cantarell that involved 20 new wells, as well as dehydration and desalination plants. In 2009, the company conducted workovers on nine minor wells and three major wells, and installed both a well recovery platform and compression equipment.

With enhanced oil recovery equipment in place, Pemex has managed to slow the decline of Cantarell field from 34.2% in 2009 to 22.6% in 2010. But it is clear that only slowing the decline will not compensate for the loss of production from Cantarell. For this reason, Pemex launched a strategy in 2008 to diversify its production sources through a mixture of enhanced oil recovery on discovered fields and increased investment in exploration projects in other parts of the country. One of the first projects that Pemex embarked upon was the further development of Cantarell’s neighbouring offshore field, Ku-Maloob-Zaap, as it could be connected to the existing Cantarell infrastructure.

In 2011, Akal produced an average of 314,000 bbl/day, a figure that is still showing signs of steady decline, while the other fields in the integral asset Cantarell produced a cumulative average of 135,000 bbl/day. Throughout the year, 18 production wells were drilled, which enabled Pemex to keep its average number of producing wells at 213.

According to Juan Carlos Zepeda Molina, the CNH imposed an investment plan for the reduction of gas flaring, so Pemex could bring in new investment for the reinjection of gas. He says, “We are glad to see these developments but we still have to recognize that Pemex has not managed to stabilize the field and its production is still declining. They have managed to stabilize—more or less—the overall production in the entire country, but only thanks to KMZ’s increasing production, not thanks to the stabilization of Akal.”

Since the decline of Cantarell, KMZ has become Mexico’s largest producing field and it is up to Pemex to take the necessary precautions to ensure it produces oil at a stable rate and maybe, eventually, manage to reverse the country’s declining oil production.