Summary
The Rigzone Newsletter quoted the Xinhua News Agency on April 22 reporting that Petroleos Mexicanos (Pemex) said first quartet output was 2.667 million bbl/day, down 7.8%from the same period in 2008. Cantarell produced 787,000 bbl/day down 34% from last year. Cantarell is the largest producing region in Mexico. Ku-Maloob-Zaap is now the largest producer with production of 797,000 bbl/day. The Cantarell Complex which includes both offshore fields accounted for 60% of Mexico’s production. Pemex thought it would average 2.8 million bbl/day for 2009 but has now lowered that estimate to 2.6 million. Crude oil price averaged $38.92/bbl in the first quarter down from $83.94/bbl in first quarter 2008. During the quarter, Pemex sold nearly 1.3 million bbl/day in overseas markets.
Analysis
Cantarell is the largest single field in what has come to be known as the Cantarell Complex. About 35 fields comprise the complex. Ku, Maloob and Zaap are three relatively large fields located immediately to the northwest of Cantarell field. Cantarell itself has been ranked by some compilers as the sixth largest oil field in the world. One field in the complex, Ixtoc, was the scene of a disastrous fire in the late 1980s, completely destroying a semi submersible drilling rig. As for Cantarell, discovered in 1979, by 1981 was flowing 1.156 million bbl/day from 40 wells. An average well in 1981 would produce 29,000 bbl/day. Development continued with production coming from many of the fields including Ixtoc, but as flow rates fell, gas lift equipment was installed. By 1995, the average well would produce 7,000 bbl/day. The gas lift program was expanded and by 1999, total production from the complex was 1.4 million bbl/day. But reservoir pressure continued to decline. Had there been no pressure maintenance installation, by 2004, production per well would have been about 3,200 bbl/day. Under that regime, production would continue for many years at ever declining rates. Engineering studies were made to improve production rates from more than 150 wells that existed at that time. Based on a study of the Yates field in West Texas, Pemex decided to inject nitrogen gas into the dome of Cantarell. That began in May of 2000 at an initial rate of 300 million cubic feet/day and was expanded through the year with a total of four stages to 1,200 million cubic feet/day. Production comes from fractured and vugular limestone of Jurassic, Cretaceous and Lower Paleocene ages. The original estimate of reserves was 17 billion barrels but this was raised to 19.3 after the nitrogen gas had pushed the original oil/water contact back to its original position. By 12/31/2006, cumulative production was 16.6 billion barrels. In 2004, the complex produced 2.136 million bbl/day which declined to 1.525 million by 2007. Production declines as the expanding gas cap intersects the well bores. Considering that the gas/oil contact is level across the field, many wells are affected simultaneously. Today the end is near with expectations that Cantarell will become uneconomic as early as 2014 and no later than 2019. The three field sub-complex Ku-Maloob-Zaap is expected to begin its terminal decline in 2010. All in all, especially with crude oil prices down sharply, the future looks grim for the complex. The above is a history of the depletion of gas cap reservoirs with natural bottom water drive produced using modern technological techniques. A similar description could be provided for the many depletion (internal gas) drive fields that exist all over the world. This example illustrates why the total world oil crude oil capacity declines over time and why OPEC depends on it to support crude oil prices in the near term.
