A gigaton per year in the Marcellus Shale alone? Findings from the University of Virginia show we can permanently and safely dispose of much larger amounts of CO2 than previously understood using played out fracked wells. Once pumped in, most of it the CO2 does not come back out. It is captured by kerogens in shale. Kerogens are the organic pieces of the shale that hold natural gas. Take out the natural gas and put in the carbon dioxide.
The natural gas is held by electrostatic and electrostatic-like properties of atoms in a process called adsorption–with a “d.” The way kerogens work is the same as activated charcoal that is widely used to remove contaminants from air or water.
The fracking process knocks natural gas off of kerogens and it is replaced by carbon dioxide.
“The results suggest that the Marcellus shale alone could store between 10.4 and 18.4 Gt of CO2 between 2018 and 2030, which represents more than 50% of total U.S. CO2 emissions from stationary sources over the same period.” and from the final paragraph: “The United States emitted 2.32 Gt of CO2 from
stationary sources in 2010, so the Marcellus shale could hold
more than half of those emissions each year.”
“At the high temperatures and pressures found at depth, it reacts with silicate minerals in rocks to form a carbonate deposit. In the lab, the team has mimicked conditions in the Marcellus shale, a vast hive of fracking activity beneath New York state and Pennsylvania. They found that half of the CO2 injected in their experimental simulation was converted into solid carbonates within a day.”
There are many questions that remain. How will it affect gas production and economically, with a price on carbon with the Clean Power Plan carbon regulations, what is the net if it does? The paper does indicate that natural gas production may be enhanced. It also says that frackquakes could be reduced.
Tao and Clarens, Tao and Clarens, Estimating the Carbon Sequestration Capacity of Shale Formations, American Chemical Society, August 29, 2013, abstract and last paragraph.
http://pubs.acs.org/doi/pdf/10.1021/es401221j
Environmental Science and Technology
Volume 47, Issue 19, 1 October 2013, Pages 11318-11325
Estimating the carbon sequestration capacity of shale formations using methane production rates (Article), Civil and Environmental Engineering, University of Virginia, Thornton Hall, 351 McCormick Road, Charlottesville, VA 22904, United States
Abstract
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. © 2013 American Chemical Society.