Some of you guys need to educate yourself on what a gas kick is. Nothing to do with inert or non-inert. It's a pressure thing caused by either density differences in the fluid (CO2 vs methane vs water) or by other effects such as disequilibrium compaction.
Also the CO2 issue is not an either/or scenario. Even if there's only 15% CO2 in the gas, it can make the accumulation uneconomic...