Review of the Hydrogeological Controls on Coalbed Methane (CBM) and Development Trends

Table 1

Conditions for identifying different hydrodynamic zones.

Identification condition	Strong runoff zone	Medium runoff zone	Stagnant zone
Fault development characteristics	Strongly fractured fault with a high hydraulic conductivity	Fractures and faults distributed within the zone with a relatively low hydraulic conductivity	No fractures or fewer fractures within the zone
Connection with surface water	Close relationship between the surface water in the zone and the aquifer	Hydraulic relationships between part of the surface water in the zone and the aquifer	No hydraulic relationship between the surface water and the aquifer
Water type	SO4·Cl^-–Na·K	HCO3·Cl–Na·K	Cl–Na·K
Converted hydraulic gradient	>0.3 m/m	0.1~0.3 m/m	Less than 0.1 m/m
Salinity	Low	Medium	High