Influence of Overlying Caprock on Coalbed Methane Migration in the Xutuan Coal Mine, Huaibei Coalfield, China: A Conceptional Analysis on Caprock Sealability

Table 2

The total thickness of each cap rock from surface drilling holes.

Surface drilling	(m)	(m)	(m)	(m)	(m)
75-7	351.6	80.1	31.6	8.6	33.3
74-7	434.2	0	41.1	62.2	41.1
74-11	354.5	32.5	46.2	27.1	114.7
67-11	350.1	55.2	24.9	46.4	120.7
73-14	348.2	0	18.4	66.7	138.6
75-8	386.7	108	35.2	26.3	55.8