Improving MMP by co-injection of miscible CO₂ with Abu Dhabi crude oil

Miscible CO₂ injection is a method to increase oil production. Combinations of Carbon dioxide with other gases as miscible solvents are emphasized in this paper to improve CO₂ miscible injection process. Emphasis is on identifying CO₂ solvent mixtures with reduced MMP to achieve miscibility at reasonable injection pressures in Abu Dhabi fields. Two targeted crude oils (Oil 1 and Oil 2) from Abu Dhabi carbonate reservoirs are utilized. The minimum miscibility pressure (MMP) of targeted oils with mixtures of N₂, CH₄, C₂H₆, and HC rich gas of varying composition with CO₂ injection gas are evaluated through simulation. Cell to Cell and Semi-analytical (key tie lines) methods are applied using CMG simulator. Results show that miscibility is predicted to occur with multiple contact miscibility (MCM): vaporization and/or condensation mechanisms. The increase of C₂H₆ concentration in the CO₂ injected gas reduced MMPs for targeted Oil 1 by 100 psi/10 mol%. However, N ₂, CH₄ and HC rich gas increments in CO₂ injected gas increased the MMPs for targeted Oil 1. MMP was observed to be 2300 psi for pure ethane with Oil 1. In addition, MMPs for targeted oils with N ₂/ C₂H₆ and N₂/ CH₄ injected gas mixtures are assessed. This study can open possibilities for future enriching of CO₂ and N₂ miscible injection to improve miscibility and recovery of oil.