Abstract

Naturally occurring carbon-dioxide (CO₂) gas has been produced from two fields in northeast New Mexico, the Bravo dome (Bueyeros) field of southern Union and southern Harding counties, and the Des Moines field of northwest Union County. Only the Bravo dome field is currently active. In addition, several wildcat wells drilled in Union, Harding, Colfax, Mora, and San Miguel counties have encountered CO₂ in Permian and Triassic red bed sequences.

The Bravo dome field is one of the principal CO₂ accumulations in North America. It is located less than 200 miles from enhanced oil recovery projects in West Texas, to which the CO₂ is transported by pipeline.

The Bravo dome is a faulted, southeast-plunging, basement-cored anticlinal nose. It is bordered on the east and south by large high-angle faults of Pennsylvanian and Wolfcampian (Early Permian) age. The principle reservoir in the Bravo dome field is the Tubb sandstone (Leonardian-Permian) at depths of 1,900 to 2,950 feet. The Tubb consists of 0-400 feet of fine to, medium-grained, well-sorted, orange feldspathic sandstone. It rests unconformably on Precambrian basement on the highest parts of the Bravo dome. The Cimarron Anhydrite conformably overlies the Tubb and is a vertical seal. Drape of Tubb sandstone over the dome created structural closure on the northeast, southeast, and southwest flanks of the field. The reservoir is sealed on the northwest flank of the field by a facies change to muddier sediments. Internally, the Tubb reservoir is divided into at least seven pressure systems, which may be bounded by small faults.

The Des Moines field produced from five wells through the late 1960s. Most production was obtained from the Abo Formation (Permian) at 2,000-2,600 feet. Areal extent of this accumulation has not been well defined.

The source of the CO₂ produced from the Bravo dome field is enigmatic, but available isotopic and geologic data suggest a juvenile or magmatic source.