Hydraulic Fracturing Test
The hydraulic fracture tests were conducted on core plugs with 37-54 mm diameter and approximately 65-75 mm length, with 4 mm diameter axial injection hole. The samples were triaxially loaded through three confining pressure steps. in this case the axial stress is 10 percent higher than the value of confining pressure.
A rubber sleeve prevented was used to inject the fluid (hydraulic oil) into the sample for increasing the confining pressure. The axial hole was pressurized with a constant injection rate of 0.015 cc/s until a hydraulic fracture was induced at the breakdown pressure. The values of axial stress and confining pressure were recorded by digital data acquisition system.