The development charactecistics of deep coal structure in northern Shizhuang area

Loose coal structure can easily make the wall of the borehole collapsed, having great impact on the exploitation of coalbed methane. So analysis of coal structure is very important. Aiming at the deep coal seam in Shizhuang, according to artificial gamma, acoustic time difference, natural gamma, caliper, the breakage of roof and floor, we classified the structure of seams No.3 and No.15 in northern Shizhuang area. The average thickness of powdered coal of seam No.3 is 1 m, accounting for 17.85% of the total thickness of the seam. And it develops in the top or the bottom of the seam. Compared with seam No.3, seam No.15 has more powdered coal, accounting for 20.81% of the total thickness of the seam, and powdered coal develops often in the top or the bottom of the seam and near dirt band. The powdered coal is mainly affected by fold. The powdered coal thickness decreases and then increases with the depth. And the knee point is 1 200~1 300 m. Consequently, the coal structure of Shizhuang is very complex. We must pay attention to it during the exploitation.