The Southwest Region is energy-rich and possesses some of the largest population and energy-production growth rates in the nation. Two major pipeline networks transport more than 27 million metric tons (30 million tons) per year of natural subsurface CO2 from Southern Colorado and Northern New Mexico to petroleum fields in the Permian Basin, where it is used for enhanced oil recovery (EOR). The 10 largest coal-fire power plants in the region produce about 127 million metric tons (140 million tons) per year. Other point sources (identifiable points of discharge) include natural gas processing plants, refineries, and ammonia/fertilizer, ethylene and ethanol, and cement plants.

Graph 1: CO2 sources by state. (Scale is in metric tons.)

SWP Coal Seams

The San Juan Basin (SJB) in New Mexico is one of the top basins in the world for CO2 coalbed sequestration because it has: 1) advantageous geology and high methane content, 2) abundant anthropogenic CO2 from nearby power plants, 3) low capital and operating costs, 4) well developed natural gas and CO2 pipeline systems, and 5) local companies with coalbed methane (CBM) and enhanced coalbed methane (ECBM) sequestration expertise. Because of its enormous coal resource, the SJB offers a tremendous sequestration opportunity with value-added natural gas production. An extensive CO2 infrastructure is already in place, making the area ready for future operations.

The coals in the SJB fairway area are of exceptionally high permeability. Due to the tendency of coal to swell when in contact with CO2, high initial coal permeability is required to maintain high CO2 injection rates over time. Maintaining high injectivity is an important requirement for large-scale, low-cost CO2 sequestration in coal.

SWP Oil and Gas Reservoirs

The Aneth oil field, discovered in 1956, is one of the largest in the nation. The Aneth Unit is part of the greater Aneth field and is located in the Paradox Basin in Southeastern Utah. Aneth is a stratigraphic trap with fractures and minor faults. The Aneth Unit covers about 16,800 acres of the northern section of greater Aneth and has produced about 149 million barrels of an estimated 421 million barrels of oil in place. The pilot test site is located within the Aneth mound complex. The primary CO2 sequestration target is the Pennsylvanian Desert Creek and overlying Ismay members of the Paradox formation, the primary producers in the Greater Aneth Field.

In Texas, the SACROC oil field unit produces from Pennsylvanian-age strata. The SACROC oil field unit lies along a trend of fields described as the Horseshoe Atoll Play. Target reservoirs in this unit include the producing Pennsylvanian carbonates.

Farnham Dome, an elongated surface anticline located along the northern plunge of the San Rafael uplift, contains numerous saline formations for large scale CO2 injection. Target formations for this site include White Rim (Permian-aged) sandstone and Wingate (Jurassic-Triassic-aged) sandstone. Saline formations make up a large portion of the United States' carbon storage capacity (estimated at 919 billion metric tons), with the added benefit of being in close proximity to CO2 point sources.

SWP Terrestrial Opportunities

In conjunction with the SWP's enhanced coalbed methane sequestration (ECBM) test, a terrestrial pilot test is being conducted in the SJB. ECBM operations are notorious for producing huge volumes of water. This water source could potentially be desalinated and used for irrigating a riparian restoration project, forming a combined ECBM-terrestrial sequestration project. Though the desalination process is an expensive one, the U.S. Bureau of Land Management and ConocoPhillips are both interested in making beneficial and environmentally-friendly use of the produced water.

Rangelands in the SJB have the potential of being large carbon reservoirs in addition to their value as recreational lands. The challenges to achieving their potential lie primarily in the limited growing conditions and reduced capacity for recovery. Optimizing carbon storage in soils and vegetation while increasing the value of other ecosystem services requires a two-pronged strategy: enhancing existing and reintroducing woody plant species along riparian areas and reestablishing native grasses and shrubs in upland areas. The limiting factor in both cases is water. A reliable source of water for agricultural irrigation, such as the water produced during ECBM production, could provide the necessary base for the reestablishment of native vegetation with a host of environmental benefits in addition to carbon sequestration. In addition to the terrestrial pilot test, the SWP is also conducting an extensive terrestrial analysis of the region.