Optimization of abandoned gob methane drainage through well placement selection

•Simulated experimental system for abandoned gob methane drainage was developed.•Spatial distribution of permeability of overlying coal rock masses above the gob was obtained.•Simulation experiment on AMG drainage was conducted to get reasonable well location.•This AMG drainage technique was applied in the Yangquan Coal Mine No. 3, China.

Abandoned gob methane (AGM) is not only a greenhouse gas but also a source of clean energy. To optimize the vertical well location for AGM drainage, AGM drainage simulation experiments for different well locations were carried out using the “simulated experimental system for AGM drainage”. A numerical model using FLUENT for AGM drainage was established. The control range of vertical wells at different well locations was determined using the results from the numerical model. The simulation experiment results showed that the O-ring fissure zone is the most suitable area for the location of the vertical well. Yangquan Coal Mine No. 3 in China is an abandoned coal mine with massive coalbed methane reserves. Vertical well #1 in Yangquan Coal Mine No. 3 was located within the O-ring fissure zone according to the simulation experiment results. The field test results for vertical well #1 showed that the gas flow rate reached 3.77 m3/min, and AGM production reached 33,000 m3 in total after 226 h of suction. In order to achieve a higher gas concentration, the gob burial depth should be taken into account during abandoned gob methane drainage.