Experimental supercritical CO2 and water interactions with coal under simulated in situ conditions

Geological storage of CO2 is a key component of emission reduction strategies. Options for geosequestration include injecting CO2 into oil and gas fields (producing or depleted), deep saline formations and coal seams. We have investigated injection of CO2 into coal using static batch experiments conducted under temperature and pressure conditions similar to the in situ formation conditions for the coal samples. Within a custom built batch reactor, sister sample coal cubes (15 mm) were immersed first in water only, and then a mixture of supercritical CO2 and water (s CO2–H2O). The s CO2–H2O experiment fluid chemistry indicates significant mobilisation of metals due to dissolution of cleat and matrix mineral matter, as well as displacement of ion exchangeable metals. Minor minerals within coal can be major constituents within the reaction fluids analysed. SEM images have provided evidence of the dissolution of both cleat and matrix minerals, as well as coal swelling and contraction induced by CO2 adsorption and desorption, respectively