Experimental study on directional fracturing by slotted hydraulic blasting in underground drilling

Abstract

This paper proposes a method for creating a three-dimensional (above-ground and underground) fracture network in deep coalbed methane (CBM) reservoirs, which is the directional fracturing by slotted hydraulic blasting in underground drilling. First, theoretical analysis was conducted to explain the mechanism by which the slotted borehole enables the separation and incidence of explosive shock wave at the slot tip, resulting in the superposition of two sub-stress waves to cause directional fracture and damage to the rock. Then, LS-DYNA was used to simulate the process of directional fracturing by slotted hydraulic blasting to verify the theoretical mechanism. Finally, similar simulation experiments were performed on traditional blasting and slotted hydraulic blasting to confirm the directional fracturing effect of the proposed method. The results indicate that the slotted hydraulic blasting method can predominate the fracture orientation under formation stress, creating extensive directional fractures in rocks in the slot direction. This study is supplemental to the efforts on directional fracturing of rocks and provides a new approach for efficient exploitation of CBM.

Keywords

• Slotted blasting
• Hydraulic blasting
• Directional fracture
• Numerical simulation
• Similar simulation experiment