Longwall-induced deformation could compromise the stability of shale gas wells positioned in the abutment pillars of current and future coal reserves. Consequently, gas from the casing(s) could flow towards the mine increasing the risk of explosive gas accumulation beyond the mandated limits. To assess the impact of this hypothetical scenario, the permeabilities of the surrounding strata is required to quantify potential gas flow to the mine. However, mining depth varies for different coal reserves could significantly impact permeability. Therefore, this study presents an analysis of longwall induced permeability under shallow, < 152 m (< 500 feet), and deep cover, >274 m (>900 feet) using measurements obtained from different study sites in Southwestern Pennsylvania along with discrete fracture network (DFN) modeling in 3DEC and Fracture Flow Code (FFC). The field study measured permeability changes for specific strata and the numerical model predicted the permeability for all the strata in the overburden. At the study site, the maximum permeability measured at the Uniontown horizon is 2.17×10-14 m2 (22 mD) and 2.42×10-13 m2 (246 mD) for deep and shallow cover site, respectively. These findings provide measure of comparing the potential risk of a hypothetical breach under a shallow and deep cover.
