High concentrations of carbon dioxide in natural gas occur when carbon dioxide is used for enhanced oil recovery (EOR). The separation of the CO2 from the hydrocarbons in the natural gas is complicated by the existence of an azeotrope between ethane (C2) and CO2 at the cryogenic temperatures required for distillation. A two-column extractive distillation system using higher molecular weight hydrocarbons as the solvent is used to remove CO2 out the top of the extractive column. Ethane is recovered from the top of the recovery column, whose bottoms is a C3+ hydrocarbon mixture called natural gas liquid (NGL). A portion of the bottoms is used as the solvent fed near the top of the extractive column. The purpose of this paper is to develop an effective plantwide control structure for this two-column extractive distillation system. Results show that a conventional extractive distillation control structure using single-end temperature control in both columns and solvent-to-feed and reflux-to-feed ratios does not provide tight control of the CO2 distillate composition from the extractive column. A composition controller is required, but two important issues must be addressed: (1) which of the two impurities (heavy-key component C2 or a heavy component in the solvent) should be controlled and (2) which of the two available manipulated variables (solvent-to-feed and reflux-to-feed) should be used.