A New Calculation Method of Minimum Gas Volume Flow Rate for Gas Drilling

Nowadays, gas injection rate for gas drilling is mainly calculated by means of Angel model, but its calculation results are frequently lower than the actual gas injection rates. Therefore, this paper firstly calculates the minimum flow rate necessary for cutting carrying based on the minimum velocity theory, and then calculates the minimum gas volume flow rate required for gas drilling by means of minimum kinetic energy method, the effects of gas flow rate and annulus cross-sectional area on the minimum gas volume flow rate in gas drilling have been analyzed, and particle group coefficient and resistance coefficient are introduced to correct the calculation results, so as to keep the minimum gas injection for gas drilling more accurate. The calculation results indicated that the corrected model is much more accordant with the practical situations than the Angel model, and the calculated minimum gas volume flow rate for gas drilling is greatly affected by the penetration rate and the borehole size.