Improved kinetic modeling of the early generation of CO2 from the Boom Clay kerogen. Implications for simulation of CO2 production upon disposal of high activity nuclear waste

Abstract A new kinetic model accounting for the generation of “early” CO 2 from kerogen within the Boom Clay Formation (Oligocene, Belgium) was developed and calibrated using a large set of experimental pyrolysis data. The model also was constrained by the present day temperature of the clay where no CO 2 generation is assumed. The kinetic scheme involved three competitive reactions characterized by relatively low activation energies, i.e., E a 2 per gram of organic carbon. Focusing on the fastest reaction specifically, this study showed that the earliest stage of CO 2 formation is associated with the thermal decomposition of moieties containing activated carboxylic acid functions present in the thermolabile fraction of the kerogen. Considering the temperature elevation within the Boom Clay Formation that would be imposed by the presence of a nuclear waste repository, the kinetic model predicts that (i) CO 2 release would start about 1 year after disposal, and might reach the limits of the clay layer after about 100 years and (ii) for each meter length of gallery, the absolute cumulative mass of CO 2 generated in a radius of 50 m around the gallery might reach ca. 3 tons.