| Description |
With the consistently growing demand for liquid hydrocarbons there have been new technologies to meet those demands. Some of the new technologies focus on removing a resource from an underground repository using some form of thermal treatment to pyrolyze the material in the formation, either coal or oil shale, to create and produce hydrocarbons. In order to offset some of the carbon dioxide that would be produced in heating underground formations, the possibility of long-term sequestration was investigated for the remnants of said pyrolysis processes. There are four mechanisms for subsurface storage of CO2: adsorption, mineralization, pore volume storage, and dissolution into the connate water. Sequestration in a pyrolyzed coal seam relies heavily on the adsorption of CO2 and is similar in concept to enhanced coal bed methane. Utah Skyline bituminous, Illinois Carlinville bituminous, and Wyoming North Antelope subbituminous coals were pyrolyzed to final temperatures of 325, 450, or 600°C with heating rates of either 10 or 0.1°C/minute. Adsorption isotherms, pore size studies, and permeability measurements were performed on the reacted and unreacted coals. The adsorption of CH4 and CO2 on the thermally treated coals increases with treatment temperature and is related to the pore size distributions. Pore size studies found a fraction of the surface area and micro- and mesopores can are attributable to residual tars. Permeability measured on the treated coals generally shows increases with treatment temperature. Sequestration in a pyrolyzed oil shale demonstrates all four sequestration mechanisms. Mineralization studies were carried out with a retorted Green River oil shale in the liquid and gas phase. Results of the mineralization study showed that the dissolution of pyrrhotite with siderite was the most prevalent path for CO2 mineralization. The combined effects of mineralization, pore volume, and adsorption were also simulated and found the most common result to be 40 kg/tonne of CO2 stored. |
