Research Article

Hydraulic Fracture Propagation and Permeability Evolution in the Composite Thin Coal Seam

Figure 5

The distribution of permeability coefficient in the vertical direction during hydraulic fracturing.
(a) Fluid-injection pressure: 3 MPa
(b) Fluid-injection pressure: 5.4 MPa
(c) Fluid-injection pressure: 8.2 MPa
(d) Fluid-injection pressure: 8.2 MPa (continuous injection of fluid)