Flow fields in the blowout of natural gas wells containing carbon dioxide

The flow fields of the blowout of natural gas containing carbon dioxide were analyzed by using fluid dynamics theory and computational fluid dynamics (CFD) technology so as to provide scientific foundation for safe distance determination. Dispersion mechanisms of blowout flow field at each stage, boundary conditions and numerical algorithm for simulation were presented as well. The process of well blowout can be divided into six stages. They are critical flux, equal entropy expanding, compressible ejection, incompressible ejection, heavy gas dispersion, and normal dispersion. The distribution of gas velocity field was got via CFD simulation, and the flux velocity can be more than 700 m/s. The concentration of CO₂ was analyzed, indicating that in the inner layer of the equal entropy expanding area, the concentration is uniform, while in the external layer, the concentration declines sharply. The correlation between mass concentration of CO₂ and dispersion distance obeys the Gauss formula. The theoretical predictions were consistent with the results of simulation, showing that the theoretical analysis of flow field and the CFD simulation method are practical.