In 1972 a fisherman named Rudesindo Cantarell reported an oil slick that was flowing from a seep in the Bay of Campeche in the Gulf of Mexico about 100 km (60 miles) off the coast of the Yucatán Peninsula. From that slick the first field in the Cantarell complex was discovered in 1976, and production began from the fields in 1979. Cantarell was the second-highest-producing field (2.14 MMbbl/d in 2004) in the world behind the Ghawar Field in Saudi Arabia.

That one discovery was a game changer for Mexico, shifting the country from an importer of crude oil to an exporter. According to the U.S. Energy Information Administration (EIA) April 24, 2014, Cantarell's “output has been declining significantly for almost a decade. Production at Cantarell began in 1979 but stagnated as a result of falling reservoir pressure. In 1997, Pemex developed a plan to reverse the field’s decline by injecting nitrogen into the reservoir to maintain pressure, which was successful for a few years.

“However, production resumed a rapid decline beginning in the middle of the last decade—initially at extremely rapid rates, and more gradually in recent years. In 2013 Cantarell produced 440,000 bbl/d of crude oil, which was nearly 80% below the peak production level of 2.1 million bbl/d reached in 2004,” EIA added.

“As production at the field has declined, so has its relative contribution to Mexico's oil sector. Cantarell accounted for 17% of Mexico’s total crude oil production in 2013, compared with 63% in 2004,” EIA continued.

Cantarell reservoirs formed by meteor

There are four fields that comprise the Cantarell complex—Akal, Nohoch, Chac and Kutz. More than half of Mexico's oil production comes from two offshore fields in the Bay of Campeche—Cantarell and Ku-Maloob-Zaap (KMZ). The oil from these fields is heavy and marketed as Maya blend.

Oil is produced from the floating storage and offloading (FSO) vessel Ta ‘Kuntah. The FSO vessel has a throughput capacity of 800,000 bbl/d and can perform both tandem and side-by-side offloadings. In 2005, the field hit 500 MMbbl of production and 1 Bbbl in 2008.

Its meteoric rise in production began with an asteroid impact. The meteor caused the Chicxulub Crater. The reservoirs are formed from carbonate breccia of Upper Cretaceous age that was rubble from the impact. “The breccia is from a shelf failure [underwater landslide] when the meteor hit. The 950-ft [289.6-m] thick rubble became the reservoir for one of the largest fields in the world. The lowermost part of the field is a Lower Cretaceous dolomitic limestone. The field is made up of a number of sub-fields or fault blocks,” according to Glenn Morton in an August 2004 article.

Efforts to boost production

Production from the field has been anything but steady. Declines in production have been followed by injections of capital to increase the daily output. In 1981 the field was producing 1.16 MMbbl/d. However, the production rate dropped to 1 MMbbl/d in 1995.

A nitrogen injection project began in 2000, increasing production from 1.6 MMbbl/d to 1.9 MMbbl/d in 2002, rising to its peak in 2004 of 2.1 MMbbl/d. However, production rates could not be maintained and began to decline rapidly in the second half of the decade. By 2010 production had plummeted by 74% to 558,000 bbl/d.

Pemex continued to provide optimistic forecasts for the field even though production continued to decline. For example, in 2008 it expected Cantarell’s output to decline until 2012 and then stabilize around 500,000 bbl/d. However, the average annual production was 500,700 bbl/d in 2011, dropping even farther in 2012 to 454,100 bbl/d.

Production was then expected to stabilize at 400,000 bbl/d. Production continued to drop to 340,000 bbl/d in June 2014.

In July 2014 Pemex announced plans to spend $6 billion by 2017 to maintain current levels of production and keep the production level at around 325,000 bbl/d. The company expects to recoup its investment over the next 10 years. The tertiary recovery project is targeting an additional 100,000 bbl/d from the Akal Field.

In May 2014 output from the Akal Field was about 189,000 bbl/d. The EOR project is expected to keep the field’s production between 180,000 bbl/d and 200,000 bbl/d for the next decade.

Cantarell’s position as the largest producing oil field in the country was eclipsed by the KMZ Field in 2009. KMZ’s annual average was 808,000 bbl/d compared to Cantarell’s 684,800 bbl/d. The KMZ Field was producing 855,100 bbl/d in 2012.

Pemex was focusing its efforts on the KMZ development, which can use the existing facilities at Cantarell.

With the recent energy reform in Mexico, mature fields like Cantarell could get a boost in investment from foreign firms. By bringing in foreign technology, Pemex could both boost production from Cantarell and extend its life even further.