AFXNews. An internal study reviewed by The Wall Street Journal shows water and gas are encroaching more quickly than expected in Cantarell, Mexico's biggest oil field, and might cause output to drop precipitously over the next few years. Currently, Cantarell produces 2 mln barrels of oil a day, or six of every 10 barrels produced by Mexico, and is the world's second-biggest-producing field after Saudi Arabia's Ghawar. Pemex says it is confident it can make up for any decline at Cantarell by squeezing more output from other fields, but some analysts outside the company are far less sanguine. The study was carried out last year by Pemex experts.