356 fracture-developed zones in the goaf), and the wellbore radius as r = 0.038 m. When the injection pressure exceeded 0.6 MPa, the calculated permeability ranged from 8.86 × 10⁻⁵ to 1.04 × 10⁻⁴ cm/s and exhibited stable values, indicating that the goaf has moderate permeability. (a) (b) Figure 3 – Results of the injection test; (a) pressure and temperature variations, (b) injection pressure and injection rate Table 1 – Evaluation of permeability Injection pressure Injection rate Permeability (MPa) (m3/s) (cm/s) 0.1 4.08×10-4 2.53×10-4 0.2 5.65×10-4 1.75×10-4 0.3 6.01×10-4 1.24×10-4 0.4 6.55×10-4 1.02×10-4 0.5 6.43×10-4 7.98×10-5 0.6 8.56×10-4 8.86×10-5 0.7 1.09×10-3 9.71×10-5 0.8 1.26×10-3 9.74×10-5 0.9 1.50×10-3 1.03×10-4 1.0 1.68×10-3 1.04×10-4 1.2 1.79×10-3 9.24×10-5
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