Methane Extraction from Abandoned Mines by Surface Vertical Wells: A Case Study in China

Table 1

Coal seam occurrence in the Yongan mine.

Coal seam number (#)	Coal seam thickness (m)	Coal seam distance (m)		Roof lithology	Floor lithology	Workability
	Minimum– maximum; Average	Minimum–maximum; Average
3	6.1–6.8; 6.3	42.6–63.2; 53.2		Mudstone Siltstone	Mudstone Siltstone	Completely minable
9	0.3–1.0; 0.6		21.0–34.1; 28.1	Mudstone Siltstone	Mudstone Siltstone	Partially minable
15	2.4–4.0; 3.0			Limestone	Mudstone Siltstone	Partially minable