Petroleum geology of the Las Vegas Basin, an overview
R. F. Broadhead
The Las Vegas Basin occupies approximately 2000 mi2 (5180 km2) in north-central New Mexico. Although present basin geometry originated during Laramide compressive tectonism, most of the more than 10,000 ft (3048 m) of sedimentary fill is Pennsylvanian in age and was deposited in the Rainesville trough, the Pennsylvanian precursor of the Las Vegas Basin.
Commercial gas production has been obtained from the Dakota Sandstone and sandstones of the Morrison Formation (Jurassic) at the Wagon Mound field in east-central Mora County. The eight wells in the field produced a total of 97 million ft3 gas from 1976 until field abandonment in 1979. The Graneros Shale (Upper Cretaceous), which overlies the Dakota Sandstone, is the probable source rock.
Shows of hydrocarbon gas have also been encountered in Pennsylvanian strata. The Pennsylvanian consists of up to 6500 ft (1981 m) of dark-gray and red shales, sandstones, minor conglomerate and minor marine limestones. The dark-gray shales constitute thermally mature petroleum source rocks with up to 9.5% total organic carbon (TOC). Kerogens are primarily gas prone. The Pennsylvanian section is within the thermogenic window in the deeper parts of the basin. Sandstones interbedded with the source rocks are the primary reservoir targets. Reservoirs domed upward by the Turkey Mountains uplift have trapped CO2 gas that was transported into the basin by magmas that formed the laccolith at the core of the uplift.
The Sangre de Cristo Formation (Lower Permian) may hold petroleum potential in any areas where dark-gray shales are present. These dark-gray shales may contain sufficient organic matter to act as source rocks where thermally mature. Post- Sangre de Cristo Permian strata, Triassic strata, and the Entrada Sandstone (Jurassic) are devoid of petroleum source rocks. Gases in these units are CO2-rich.
- Broadhead, R. F., 2015, Petroleum geology of the Las Vegas Basin, an overview, in: Geology of the Las Vegas Region, , New Mexico Geological Society, Guidebook, 66th Field Conference, pp. 253-260.