Gas volume control techniques for circular gas drilling

The study of wellbore gas volume control may be helpful to enhance the efficiency of circular drilling, reduce the difficulty in controlling the pressure of equipment, provide a reasonable plan to add or discharge gas for circular drilling, and guide the control of node pressure. Based on the characteristics of circular closed gas drilling, the study of wellbore pressure of circular drilling in different injection conditions is conducted. Using the research results of pressure distribution, on the basis of the gas P-V-T theory, the model to calculate the circular gas volume in the wellbore is set, and the gas mass distribution in the wellbore under dynamic conditions is studied. Based on the above-mentioned study, combined with the Ground equipment control requirements, the reasonable area of wellbore gas control is determined. Research results show that the unit footage gas volume increases with the increase of well depth, meanwhile, the reasonable gas window expands gradually. There will be negative wellhead pressure, if the gas volume in the wellbore gets insufficient.