**Experiment 1 (powerhouse upstream)**

In trial 1, the experiments were conducted in the EX-size hole at the depth of 10–16 m where the rock mass was completely fractured. This particular zone was selected after careful observation of core logging data. The injection unit was placed at this depth for the pressurization. The pressure was injected at a rate of 6 l/min for a duration of 50–250 sec and the pressure was instantaneously increased up to 50 bars. Critical pressure could not be reached which eventually dropped to zero at the end of cycle. The shut- in pressure could not be achieved even though the pump was shut-off at certain peak levels (**Figure 9**). It clearly indicated that water has

**Figure 8.** *Tracing of fractures from impression packer at powerhouse downstream area.*

**Figure 9.** *Experiment 1.*

been escaped from the existing fractures and the required pressure could not develop to reopen the fracture. Normal stress required for reopening of the pressure could not build up across the fracture. The pressure time diagram for the flow rate of 6 l/min is given below (**Figure 9**).

#### **Experiment 2**

In trial 2, the experiments were conducted in the EX-size hole at the depth of 10–16 m where the rock mass was completely fractured. This particular zone was selected after careful observation of core logging data. The injection unit was placed at this depth for the pressurization of the zone. The pressure was injected at a rate of 9 l/min for a duration of 50–250 sec and the pressure was increased up to 60 bars. Critical pressure could not be reached but there was a decline in the pressure which eventually dropped to zero at the end of cycle. The shut- in pressure could not be achieved even though the pump was shutoff at certain peak levels (**Figure 10**). It clearly indicated that water has been escaped from the existing fractures and the required pressure could not develop to reopen the fracture. Normal stress required for reopening of the pressure could not build up across the fracture. The pressure time diagram for the flow rate of 9 l/min is given below.

**Figure 10.** *Experiment 2.*

*Hydraulic Fracturing in Porous and Fractured Rocks DOI: http://dx.doi.org/10.5772/intechopen.106552*

**Figure 11.** *Experiment 3.*

### **Experiment 3**

In trial 3, the experiments were conducted in the EX-size hole at the depth of 10–16 m where the rock mass was completely fractured. This particular zone was selected after careful observation of core logging data. The injection unit was placed at this depth for the pressurization. The pressure was injected at a rate of 12 l/min for a duration of 50–250 sec and the pressure was increased up to 70 bars. Critical pressure could not be reached but there was a decline in the pressure and which eventually dropped to zero at the end of cycle. The shut-in pressure could not be achieved even though the pump was shutoff at certain peak levels (**Figure 11**). It clearly indicated that water has been escaped from the existing fractures and the required pressure could not develop to reopen the fracture. Normal stress required for reopening of the pressure could not build up across the fracture. The pressure time diagram for the flow rate of 12 l/min is given below.

#### **Experiment 4**

In trial 4, the experiments were conducted at the same depth of 10–16 m where the earlier experiments were conducted with the flow rate of 6, 9 and 12 l/min. But in this case the flow rate was instantaneously increased to 15 l/min. The pressure was injected at a rate of 15 l/min for a duration of 80 sec and the pressure was automatically increased up to 95 bars. In the first cycle a clear critical pressure could be reached and there was no declining of pressure abruptly. Shut in pressure obtained at 50 bars after the pump was shut off. It clearly indicated that water flow has been required 15 l/min for the existing fractures to reopen.

Where *P*si is the shut-in pressure, represented as the point of intersection between the tangent to the pressure curve immediately after pump shut-off and that to the late stable section of the pressure curve (**Figure 12**) (Enever and Chopra, 1986). The pressure time diagram for the flow rate of 15 l/min is given below (**Figure 13**).
