Evaluation of Gas's Carrying Capacity and Erosion Ability in Air Drilling

Air as a drilling fluid has the advantages of protecting reservoirs from being damaged by liquid drilling fluids,enhancing ROP,mitigating and avoiding lost circulation. On the other hand,the carrying capacity of and drill-string erosion by air are difficulties obsessing drilling engineers. A numerical model is established for the flow of fluid in holes drilled with air,and a simulation of borehole gas-solid two phase flow field is performed combined with drilling data obtained from drilled wells. Combining the minimum velocity of cuttings carrying and critical erosion velocity criteria,flow field in bore hole is qualitatively evaluated. The work provides a base for practical drilling design.