Pemex exploratory drilling has fallen to its lowest in 29 years, a warning sign for Mexico's future oil reserves even as the company's finances improve.

Pemex exploratory drilling has fallen to its lowest in 29 years, a warning sign for Mexico's future oil reserves even as the company's finances improve.

The filing names five fields running dry. Total reserves rose slightly last year, but only because gas climbed while crude oil fell 2.6 percent.