Carbon dioxide in Union and Harding Counties
— Ronald F. Broadhead

Naturally occurring carbon-dioxide (CO₂) gas has been produced from three fields in Union and Harding Counties: the Bravo Dome and Bueyeros fields of southern Union and southern Harding Counties and the Des Moines field of northwestern Union County. Only the Bravo Dome and Bueyeros fields are presently active. Development of the Bravo Dome and Bueyeros fields was slow until the 1980's when CO₂ became useful for enhanced recovery of oil in the Permian Basin of southeastern New Mexico and western Texas. Current CO₂ production from the Bravo Dome and Bueyeros fields is approximately 100 billion ft 3/yr. Estimates of recoverable reserves in the Bravo Dome and Bueyeros fields range from 5.3 to 9.8 trillion ft 3/yr.

The main reservoir in the Bravo Dome and Bueyeros fields is the Tubb sandstone (Permian) at depths of 2,000-2,500 ft (600-750 m). Other reservoirs are arkosic sandstones and conglomerates of the Abo Formation (Permian) at depths of 2,500-3,000 ft (750-900 m) and Santa Rosa sandstones (Triassic) at depths less than 1,000 ft (300 m). The main reservoirs in the Des Moines field are arkosic conglomerates of the Abo Formation (Permian) at depths of 2,060-2,600 ft (630-790 m). Other secondary reservoirs are in the Alibates Dolomite (Permian) at a depth of approximately 1,200 ft (370 m).