posted on 2016-02-18, 19:14authored byZhiyuan Tao, Andres Clarens
Hydraulically fractured
shale formations are being developed widely
for oil and gas production. They could also represent an attractive
repository for permanent geologic carbon sequestration. Shales have
a low permeability, but they can adsorb an appreciable amount of CO2 on fracture surfaces. Here, a computational method is proposed
for estimating the CO2 sequestration capacity of a fractured
shale formation and it is applied to the Marcellus shale in the eastern
United States. The model is based on historical and projected CH4 production along with published data and models for CH4/CO2 sorption equilibria and kinetics. The results
suggest that the Marcellus shale alone could store between 10.4 and
18.4 Gt of CO2 between now and 2030, which represents more
than 50% of total U.S. CO2 emissions from stationary sources
over the same period. Other shale formations with comparable pressure–temperature
conditions, such as Haynesville and Barnett, could provide significant
additional storage capacity. The mass transfer kinetic results indicate
that injection of CO2 would proceed several times faster
than production of CH4. Additional considerations not included
in this model could either reinforce (e.g., leveraging of existing
extraction and monitoring infrastructure) or undermine (e.g., leakage
or seismicity potential) this approach, but the sequestration capacity
estimated here supports continued exploration into this pathway for
producing carbon neutral energy.