Gas Migration Patterns with Different Borehole Sizes in Underground Coal Seams: Numerical Simulations and Field Observations

Gas flow in a coal seam is complex process due to the complicated structure and sorption characteristics of adsorbable gas (such as carbon dioxide methane). It essential understand migration patterns for different fields engineering, such CBM exploitation, underground mine drainage, CO2 geo-sequestration. Many factors influence patterns. From surface production wells, in-seam content cannot be quantified, it difficult predict total time. In order during recovery variations with respect time, solid-fluid coupled model proposed illustrate seam. Field data was collected simulation parameters were obtained. Based on this model, scenarios borehole sizes simulated both directional boreholes normal parallel seams. Specifically, 10 m, 15 20 m. The 2 4 6 Under drainage leading times, residual contents quantified. Longwall Panel 909 Wuhushan mine, one five m monitoring drilled. After six months monitoring, obtained compared results. Of gas, 61.36% drained out from first borehole. field study, effective diameter less than 8 after drainage. performance tightly affected by size determined that observations line findings study can provide similar conditions.