Located 62 miles (100 kilometers) off the coast of the Yucatan Peninsula in the Gulf of Mexico, in waters measuring 115 feet (35 meters), is Cantarell, one of the largest oil fields ever discovered. Cantarell is wholly owned and operated by Pemex Exploration and Production (PEP).

The Cantarell complex consists of four adjacent oil fields -- Akal, Nohoch, Chac and Kutz -- with Akal considered to be the most important of the four. Deemed the most significant oil field in Mexico and the sixth largest in the world, Cantarell boasts reserves totaling 35 billion. Cantarell spans 44,800 acres (70 square miles) and its reservoir is shaped like an underground volcano, making its output one of the easiest to exploit due to the field's natural pressure.

Found in 1979, Akal provides 90% of Cantarell's production. Chac was discovered in 1976, but didn't commence production until 1991, and provides roughly 4% of the field's production. Nohoch was discovered in 1978, commenced production in 1979 and contributes roughly 5% to the field's production. Lastly, Kutz commenced production in 1998 and contributes 1% to Cantarell's production.

Field History and Development

Discovered in 1976 by fisherman Rudesindo Cantarell, the field commenced production in June 1979 and reached a peak production rate of 1.1 MMbopd in April 1981 via 40 wells. The oil is sent to 16 wellhead platforms, which perform first-stage oil/gas separation, and crude is stabilized at three production complexes.

Cantarell's crude oil is sent via pipelines to tankers at Cayo de Arcas and to storage tanks onshore at Dos Bocas. Produced gas is sent onshore for treatment and then to market, with the balance returned to the field for gas lift.

Redevelopment

In 1995, Cantarell's production level started declining, reaching a level of 1 MMbopd. Pemex launched an extensive design study for the field's development in order to increase pressure within the reservoir, and help to improve oil extraction rates.

Two years later it was decided that the field would undergo a massive drilling program, consisting of 205 producing wells and eight wells for injection tied to a total of 38 wellhead platforms. To obtain this goal, the operator decided that 6 platform extensions were needed on existing drilling platforms and 10 new additional drilling platforms were to be placed in the Cantarell complex.

For Cantarell's production facilities, a design study was created through a master plan, containing two components -- a short-term plan and a long-term plan. The main objective of the short-term plan was to "increase production through facility upgrading, and de-bottlenecking existing facilities to maximize current infrastructure capacity and increase reliability of existing production facilities," according to PEP. The short-term plan included modifications to existing platforms to add new production separation facilities; pumps and compressors; and the installation of additional produced gas-compression facilities; interconnecting pipelines and an FSO.

The Gulf of Mexico's first FSO, the Ta'Kuntah receives treated crude oil and is then offloaded to transport tankers. The FSO is installed on the Cantarell field and has been operating since August 1998. Ta'Kuntah is owned and operated by MODEC and is leased by PEP.

The main objective of the long-term plan was to maximize the economic value of the field through a pressure maintenance program by injection. The plan included the drilling program; installation of new wellhead platforms; riser and injection platforms; two new central processing complexes; accommodation platforms; bridges and flares and interconnecting pipelines.

Production

Since Cantarell's reservoir contained a natural gas bubble that helped maintain the field's pressure for the first 20 years, the operator decided to inject nitrogen in order to pressurize the reservoir and increase the field's production.

The nitrogen injection project started operating in 2000 and boosted production from about a million barrels a day to 1.6 million barrels a day, then to 1.9 million barrels a day in 2002 and reached a peak rate of 2.1 million barrels a day in 2004. This made Cantarell the second-fastest producing oil field in the world, only behind the massive Ghawar field in Saudi Arabia.

Since these recovery efforts, Cantarell is now in persistent decline due to the maturity of the field. In May 2008, it was reported the field fell to 1 MMbopd, the lowest output since the recovery efforts took place. It is estimated that Cantarell will continue to decline roughly 10% a year, down to a rate of 600,000 bopd in 2013.