Resumo:

Geological sequestration of carbon dioxide (CO2) can represent an effi cient and safe long-term storage of this greenhouse-contributing gas. When applied to shales, CO2 injection can enhance shale gas recovery (CO2-ESG) and contribute to CO2 abatement through geological storage. Shale is considered an unconventional reservoir due to its reduced permeability, consequently CO2 storage in shales has peculiar characteristics: storage through adsorption into the microporosity of organic particles and clay minerals. The effi cacy of CO2 adsorption and CH4 desorption processes drive CO2 storage capacity and hydrocarbon production of organic-rich shale. Therefore, understanding gas sorption patterns in shale and how these are aff ected by its organic and inorganic composition is essential to evaluate shale’s CO2 storage capacity.organic matter quantity, type and maturation are vital parameters considering CO2 adsorption in shale because it controls organic porosity, pore size, and internal surface area within this lithology. Besides the organic component, clay mineralogy also aff ects CO2 storage capacity in shale. Expandable clay minerals, such as smectites, contribute as CO2 adsorption sites and add to shale’s overall CO2 storage capacity. Thus, such organic and mineralogical characterisation should be the fi rst step towards CO2 storage capacity assessment in shale. This chapter investigates the complexity of the interaction between the organic and inorganic components in shale with CO2. Due to the heterogeneity regarding the organic content and maturation stage of shales from Irati Formation, Paraná Basin, Brazil, these were selected as a case study in this research. Selected Irati Formation organic-rich shale samples went through the following experimental procedures: total organic carbon and Rock-Eval pyrolysis screening, paired with palynofacies, vitrinite refl ectance and spore fluorescence to characterise the organic component; followed by x-ray diff raction and scanning electron microscopy to determine mineralogical composition; together with gas sorption isotherms (BET and Langmuir methods) to characterise the porous media and CO2 storage capacity. The relation between shale’s composition and sequestration was analysed and demonstrated in this study to improve the knowledge on CO2 geological storage into organic-rich rock formations and scientifi cally communicate how these unconventional reservoirs can signifi cantly contribute to CO2 abatement.