**Author details**

Secondary Fractures and Their Potential Impacts 19

**reactivated fractures at 10cm depth from surface reactivated fractures at 10cm depth from surface reactivated fractures at 10cm depth from surface** 

(a) case 1 (b) case 2 (c) case 3

**reactivated fractures at 10cm depth from surface reactivated fractures at 10cm depth from surface reactivated fractures at 10cm depth from surface** 

(d) case 4 (e) case 5 (f) case 6

(g) case 7 (h) case 8

**Figure 9.** Reactivated fractures by thermoplasticity for different cases of Table 2 at one-third depth from the surface

Induced tensile stresses are expected to occur in rocks with significant plastic behaviour during loading and unloading of hydraulic fractures. These induced stresses can open pre-existing natural fractures in the formation and even open the cemented natural fractures. These activated fractures can provide more rock-fluid contact area. The size of these natural fractures is much less than the main hydraulic fracture but presence of these fractures in considerable numbers can significantly increase the contact area between the wellbore and formation. The path of initiation and propagation of these fractures can be induced by natural fractures. To study their effect, a three-dimensional finite element model with cohesive interfaces embedded

third depth from the surface of hydraulic fracture

**Fig. 9.** Reactivated fractures by thermoplasticity for different cases of Table 2 at one-

**reactivated fractures at 10cm depth from surface reactivated fractures at 10cm depth from surface**

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788 Effective and Sustainable Hydraulic Fracturing

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of hydraulic fracture

**6. Conclusion**

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Arash Dahi Taleghani1 , Milad Ahmadi1 and J.E. Olson2

