Study on the flow field of multi-phase coupling slag discharge and the influencing factors of slag discharge effect in gas lift reverse circulation of drilling shaft sinking

Abstract Combined with the advanced drilling of the central return air shaft in Kekegai Coal Mine, the distribution law of slag discharge flow field by drilling method and the influencing factors of slag discharge effect are studied. Firstly, the numerical model of gas–liquid–solid coupling slag discharge is established by CFD-DEM (computational fluid dynamics coupled discrete element method). Then, the flow field distribution law of the site slag outlet layout model and the optimization model is compared and analyzed. Finally, the influence of drilling parameters on slag discharge effect is studied. The results show that the best arrangement of slag suction ports is: the number is two, the length-diameter ratio is 0.4, the area ratio is 1, and the total area ratio is 1.94%. The fluid movement at the bottom of the well is mainly tangential flow, while the fluid in the slag discharge pipe is mainly axial flow. The construction parameters of efficient slag discharge are put forward: bit rotation speed is 8.7 r/min, gas injection rate is 4200 m 3 /h, air duct sinking ratio is 0.84, and mud viscosity is 165 MPa·s. The research results can provide useful theoretical reference for large-scale sinking construction in deep wells.