Technology of Composite Slag Discharge for Directional Drilling in Complicated Broken Stratum

Aiming at the problem that the directional borehole in complicated broken stratum is easy to instability and collapse in the coal mine, the mechanism of the wall in the nearly horizontal directional borehole are analyzed, and the reasons why it is difficult and easy to discharge slag in sliding directional drilling are given. The technology of compound slag discharge using large flow flushing fluid with positive circulation and irregular drill pipe with rotation is proposed. Meanwhile, this paper analyzes the composite slag discharge mechanism of large flow flushing fluid turbulent slag discharge, the drill pipe with rotation, the hydraulic power with positive circulation and the irregular drill pipe. The key equipment of the mud pump with large flow, the wireless drilling measurement system and the irregular drill pipe are introduced. In Sihe Coal Mine, 3 directional boreholes are completed in the soft and hard fractured coal seam area, with the maximum borehole depth is 270 m and the pore forming rate reaches 66.7%. In the roof with three layers of complex strata, 12 high position directional boreholes are completed, the maximum hole depth is 480 m, the pore forming rate reaches 91.7%. It provides technical support for gas drainage and utilizing in the progressive and coal mining distressing area.