Speculum Observation and Trajectory Measurement in Gas Extraction Drilling: A Case Study of Changling Coal Mine

Table 2

Basic parameters of coal seam gas drainage borehole.

Number	Coal seam	Place	Dip angle (°)	Azimuth (°)	Drilling depth (m)	Aperture (mm)	Drilling type
C5^b-C1-1	C5^b	152106 track lane, which is 1000 m and 1030 m away from the gateway	-3	350	70	75	Down bedding
C5^b-C1-2			-3	350	70	75
C5^b-C2-1		152106 track lane, which is 500 m and 530 m away from the gateway	-3	350	100	94
C5^b-C2-2			-3	350	100	94
C5^b-A3-1	C5^b	152105 track lane, which is 300 m away from the gateway	+14	230	80	75	High-level drilling
C5^b-B2-1		152105 track lane, which is 200 m away from the gateway	+14	285	80	75
C5^a-C2-1	C5^a	152106 track lane, which is 500 m and 530 m away from the gateway	+3	350	70	75	Up crossing
C5^a-C2-2			+3	350	70	75
C6^a-C2-1	C6^a	152106 track lane, which is 500 m and 530 m away from the gateway	-10	350	70	75	Down crossing
C6^a-C2-2			-10	350	70	75
C6^c-C2-1	C6^c	152106 track lane, which is 500 m and 530 m away from the gateway	-15	350	70	75	Down crossing
C6^c-C2-2			-15	350	70	75