Decades of US carbon dioxide emissions could be stored in domestic oil and gas fields

The US has room to sequester at least 2.4 teratons of carbon dioxide—hundreds of years’ worth of industrial emissions—underground, whether in saline formations, unmineable coal seams, or oil and gas reservoirs, according to a recent report from the Department of Energy’s National Energy Technology Laboratory (NETL).

Depleted oil and gas fields have more than 225 gigatons of storage capacity, enough to accommodate several decades of US CO₂ emissions from electricity generation and other stationary sources. Much of that sequestered gas could simultaneously increase petroleum production by displacing oil trapped in the depleted formations. The NETL report stated that with next-generation enhanced oil recovery an estimated 170 gigatons of CO₂ could be used to produce 60 billion barrels of oil by 2100. In addition to being well characterized, oil and gas reservoirs have an existing infrastructure for CO₂ injection.

The 2012 edition of the Carbon Utilization and Storage Atlas compiles information from DOE’s seven regional carbon sequestration partnerships and 10 site characterization projects. The report says that upwards of 56 gigatons of CO₂ could be sequestered in coal seams that are too deep, too thin, or otherwise unsuitable to be mined. Because coal adsorbs CO₂ preferentially compared to the methane that is contained there, extracting the displaced methane would also offer an economic incentive for coal seam carbon storage.

But by far the greatest capacity for CO₂ storage is in saline aquifers, the deepest and most extensive option. Capacity estimates for the saline formations, named for the briny water they contain, range from 2.l to more than 20 teratons of CO₂. But saline formations are the least characterized of the storage candidates, and no offsetting economic incentives exist.

Basalt formations and organic-rich shales are other potential CO₂ storage options being investigated by the DOE centers. No estimates are provided for their storage capacities, but the report notes that basalt could be the best permanent carbon storage option because of the likelihood that injected CO₂ would combine with the magnesium and calcium contained in the rock to form the carbonates calcite and dolomite.