Before world oil prices collapsed late last year, shop owners closest to the banks of the Rio Grande River in Piedras Negras joked that they could hear the groans of Texas drilling rigs advancing toward their fast-growing northern Mexico city.

Just seven years ago, the first well was drilled into the Eagle Ford shale formation, which is 80 kilometers (50 miles) wide and stretches northeast for 640 kilometers (400 miles) from the border, past the eastern outskirts of San Antonio. That well yielded such prodigious quantities of gas and oil it set off a frenzy of investment so intense in Texas that 11,000 more wells were completed in the 29-county drilling zone. The Eagle Ford now produces over 1.6 million barrels of oil and 7 billion cubic feet of natural gas daily, according to the U.S. Energy Information Administration, making it one of the largest oil and gas fields on the planet.

Until oil prices melted, nothing slowed the development. Not the availability of capital or drilling rigs. Not a deep Texas drought that focused public attention on the 15,000 to 19,000 cubic meters (4 million to 5 million gallons) of fresh water required to drill and hydraulically fracture each well. Not the nearly equal levels of public concern about the billions of gallons of oilfield wastewater and the choices energy development companies were making to pump the toxic liquids into deep disposal wells, some of which University of Texas at Austin researchers linked to heightened earthquake activity.

The big questions asked by northern Mexico state and business leaders are two-fold. First is whether the portions of Eagle Ford shale that reach under the Rio Grande and deep into Coahuila are capable of producing anywhere near the same quantities of fossil energy. Another question is whether difficult ecological conditions, particularly the scant reserves of fresh water in Mexico’s second driest state, are suitable to support intense drilling and development.

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