Reduced chemical kinetic mechanism (chemkin format) for the combustion of methane in a carbon dioxide/oxygen atmosphere at very high pressures (100 to 300 bar). Original mechanism is AramcoMech 2.0 ( https://www.universityofgalway.ie/combustionchemistrycentre/mechanismdownloads/aramcomech20). The reduction method is Global Pathway Selection (Gao et al, Combustion and flame, 167 (2016) 238-247).