Numerical investigation of the flow of supercritical carbon dioxide injected into the bottom hole during drilling with special emphasis on the real gas effects

Supercritical carbon dioxide jets formed in the bottom hole can assist the drilling process and a better understanding of the flow in the bottom hole is crucial for improving shale gas exploitation. A CFD model that includes the real gas effects of carbon dioxide was used to investigate the impinging flow field in the bottom hole. The simulations show that the model accurately predicts the carbon dioxide bottom hole flow in the liquid and supercritical regions which cover the typical operating ranges used in petroleum engineering. The results indicate that increasing the inlet temperature will increase the axial velocity but will slightly reduce both the mass flow rate and the impact of the carbon dioxide jet. An increase in the inlet pressure not only increase the mass flow rate and the dynamic pressure of the supercritical carbon dioxide jet but also increase both the pressure gradient and the temperature gradient along the impinging wall which are beneficial to the jet-assisted drilling process. Additionally, the Joule-Thompson throttling effects are much more prominent at higher inlet temperature and larger pressure drops. The findings reported in the paper will provide guidance for engineering applications.