The Drainage Horizon Determination of High Directional Long Borehole and Gas Control Effect Analysis

Figure 9

Drilling peep at different depths of 1-2# observation hole when working face advances to 50 m. (a) Final hole height 2 m. (b) Final hole height 6 m. (c) Final hole height 10 m. (d) Final hole height 15 m.

(a)

(b)

(c)

(d)