Lab Experiment and Field Test of Hydraulic Fracturing in Controlling Hard Roof

To obtain the crack growth law of hard roof under hydraulic fracturing, laboratory experiments were used to study the fracturing effect under the effect of different prefabricated transverse grooving parameters and pump injection rate. The experiments result shows: prefabricated transverse grooving can effectively reduce the initiation pressure, and longer grooving length and appropriate grooving angle may result in a smoother reorientation path for hydraulic fracture, thus improving the near-wellbore complexity. Besides, field experiments are also conducted to test the influence range and treatment effect. The result of field experiments shows: the propagation of hydraulic fractures ranges from 30 m to 50 m and no obvious impact pressure occurs after treatment. The roof fragments can also drop freely with the advancing of working face, which shows that hydraulic fracturing can effectively control the hard roof.