Numerical Simulation Study On Flow Field And Rock-breaking For Self-propelled Nozzle Applied In Hydraulic Deep Penetration

Research and practice indicate that, the hydraulic deep penetration technology is suitable for the development of the low permeability reservoir, fracture reservoir, and thin reservoir, etc. As the key component for rock-breaking and perforating,the nozzle is of great importance. Recoil ahead shows when the water jet from the front orifices of the nozzle impacts on the rock. It can prevent the nozzle from drilling ahead. The conventional answer to this problem is to use a motor or winch as the power device. But this can make the penetration system more complicated.The self-propelled nozzle can solve the problem mentioned above. Recoil, which is provided by the water jet from the back orifices, can be the power for drilling ahead. And the resistance produced by the clast or the fluid can be counteracted too.This theory is aiming at the design and the optimization of the self-propelled nozzle. Based on the rock-breaking mechanism under high pressure water jet,the critical parameter of rock-breaking on Yellow Sandstone is deduced. And the shear strength theory is considered. A self-propelled nozzle, applied in the hydraulic deep penetration technology, is designed. The diameter of the orifices, the angle of the orifices to the axis, and the material of the nozzle and etc are all considered.The water jet flow field model is built and simulated, the software FLOTRAN is used. The results show that rock-breaking can be achieved under the water jet coming out of the nozzle. The self-propelled process of the nozzle can be achieved. So the self-propelled nozzle can be applied in the hydraulic deep penetration technology.Based on the strike force of the water jet, a non-dimensional evaluation standard is built. The effect of the inlet pressure to the rock-breaking ability of the water jet is analyzed, and so it is with the other key parameters, such as the outlet pressure, and the diameter of the orifices, etc.The water jet rock-breaking model is built and simulated, the software LS-DYNA is used. The results show that rock-breaking can be achieved, the diameter of the rock-breaking pit is larger than the nozzle's, and accordingly the self-propelled rock-breaking can be achieved. And the velocity of the water jet at any node would fluctuate down during the rock-breaking process. Further more, the depth of the rock-breaking pit increases linearly with the increase of the water jet velocity. This illustrates that, when the structure parameters of the nozzle is certain, the depth of the rock-breaking pit can increase by increasing the water jet velocity.