One of the challenging aspects of today’s world is CO2 emissions that mainly cause global warming, climate change, and greenhouse effect. Nowadays, the innovative technology supersonic separators are used to separate CO2 from the mixture of gases and various other applications, but their applicability is limited to onshore applications only. This study aims to design a supersonic separator feasible for the actual downhole conditions. Currently, there is no existing literature on downhole applications. This study is based on hypothesis that the supersonic separators can be adapted for downhole use through optimal design, various simulation studies, and comparison of results with the existing literature. The ANSYS FLUENT is used for the analysis due to its computational efficiency. Lettieri’s CFD model is validated using the experimental data published by MIT. Lettieri’s simulation results demonstrated that the pressure ratio increases in the converging section, drops to zero at the throat during condensation, and then decreases in the diverging section of nozzle. The parameterized model proved feasibility for a variety of mesh sizes, turbulence models, and equation of state, suggesting its applicability in downhole scenarios. A mesh independence study revealed that a mesh size of 3 mm is optimal for computational efficiency. The Grid Convergence Index (GCI) underscores the accuracy and convergence of numerical solutions, particularly with fine and medium meshes. The condensation of CO2 is efficiently attained by different turbulence models. In the future, this parameterized model would be further optimized for downhole conditions by incorporating the techniques of design of experiment, response surface methodology, and multi-objective optimization.