Gas–liquid separators are one type of surface facility among those used in oil fields. In this paper, the study of gas–liquid separation in a cylindrical cyclone separator (GLCC) using computational fluids dynamics was carried out. The multiphase mixture model and the k–ε turbulence model in an air–water mixture with different geometries of the separator varying the inlet angle from 27° to 36° and 45° were used. Later, variables for the volumetric fraction, velocity, and pressure drop in the separator were studied. Finally, a natural gas mixture from a Colombian oil field was simulated using a species transport model. The results showed that a 36° inlet is the most suitable for the separation process due to its capacity to form a high-intensity swirl without produced liquid carry over. Also, it was found that the centrifugal separator could be a suitable alternative compared with conventional gravitational gas–liquid separators.