Abstract

Several major tectonic elements are present in Colfax, Mora and Taos Counties of north-central New Mexico. The Sangre deCristo uplift trends north-south through eastern Taos and western Mora Counties. The Raton and Las Vegas Basins are present east of the uplift. These two basins are divided by the east-west trending Cimarron arch. Precambrian basement in the Raton and Las Vegas Basins rises gradually eastward onto the Sierra Grande uplift. Both the Raton and Las Vegas Basins are Laramide in age but have Pennsylvanian ancestry.

Gas has been produced from the Raton and Las Vegas Basins. Late Cretaceous to Early Tertiary coals of the Vermejo and Raton Formations have produced 128 billion ft³ gas. Another 173 million ft³ gas has been produced from a single well in the Pierre and Niobrara Shales (Late Cretaceous) in the Raton Basin. On the east flank of the Las Vegas Basin, 97 million ft³ gas have been produced from the ultra-shallow Dakota (Cretaceous) and Morrison (Jurassic) sandstones at the Wagon Mound field.

The Raton Basin has significant potential for natural gas. Additional coalbed methane is expected in undrilled parts of the Vermejo and Raton Formations. Possibilities are excellent for thermogenic shale gas in the Pierre and Niobrara Shales in the deep axial parts of the basin and for shallow biogenic gas on the east flank of the basin and adjoining parts of the Sierra Grande uplift. In addition, Dakota and Morrison sandstones are excellent reservoirs and are stratigraphically associated with source rocks. Gas may also be present in Pennsylvanian strata in a postulated Ancestral Rocky Mountain basin underneath the deeper parts of the Raton Basin.

The Las Vegas Basin holds considerable potential for natural gas in the Pennsylvanian section. This section contains up to 10,000 ft of shale and sandstone and mature organic-rich source facies are present in the shale sections. Natural gas shows have been encountered in the Pennsylvanian section by deep exploratory wells. CO₂ gas is encountered in the vicinity of Tertiary-age igneous intrusions. In addition, there is potential for shallow biogenic gas in Dakota and Morrison sandstones on the east flank of the basin and on adjoining parts of the Sierra Grande uplift. Cretaceous and Jurassic sandstones hold gas potential on the shallow Cimarron arch.