Experimental Investigation on Propagation Behavior of Hydraulic Fractures in Coal Seam during Refracturing

Figure 7

Fracture morphologies under different conditions in coal seams in refracturing: (a) was small (0–2 MPa), and no new HFs were formed; (b) was large (4–8 MPa), and the stress field was not changed much and new branches were formed perpendicular to the initial HF; and (c) was large (4–8 MPa), with stress inversion, and new HFs were created in refracturing.

(a)

(b)

(c)