Analysis And Design Of The Hydraulic Impact Drilling Tool With Self-sustained Oscillation Pulsed Jet

With the rapid development of deep and complex oil and gas reservoirs,accelerating the penetration rate in deep and hard formations has become a hotspot in research since it is a very important approach to effectively improve the economic performance.In this paper,according to the practical need of engineering application,the self-sustained oscillation pulsed jet technology is introduced into the hydraulic drilling engineering to accelerate the penetration rate in deep and ultra-deep well drilling.The main mechanism of this technology is to change the pressure field distribution in the bottom hole to reduce the rock breaking strength and overcome the chip hold down effect to improve the well cleaning efficiency.The core part of this technology is the self-sustained oscillation pulsed jet generating device.The mechanism of hydraulic pulsed jet,the jet frequency characteristics and the influence of the structure parameters of the oscillation chamber and operating parameters on the pulsed jet performance are mainly discussed in this paper.Firstly,the mechanism of self-sustained oscillation pulsed jet is analyzed as well as the effective excitation conditions.According to the hydro-network simulation theory,the formula of pulse frequency is deduced.The formula indicates that the performance of self-sustained hydraulic oscillation is related to the structural parameters of the oscillation chamber and operating parameters.Secondly,the simplified model of self-sustained oscillation pulsed jet device is established based on the similarity principle of fluid mechanics and numerical simulations are conducted by CFD software.The large eddy simulation（LES）method is applied to simulate the flow field inside the oscillation chamber under the laboratory test conditions.The simulation results are quite supportive to the interpretation of the mechanism of self-sustained oscillation pulsed jet and the optimal range of structural parameters of oscillation chamber is obtained: d₂/ d₁=1.2¹.5,D_c/ d₁=5.0⁷.0,L_c / D_c =0.6⁰.7,α₁=120°¹80°.Finally,the physical model tests of self-sustained oscillation pulsed jet device are carried out to verify the accuracy of numerical simulation results.The results of laboratory tests indicate that optimal range of structural parameters is generally in agreement with the numerical simulation results.In addition,the frequency characteristics of the pulsed jet are further analyzed and the calculation formula of pressure drop is derived according to experimental results.Based on the deep well drilling operation,the optimization design of hydraulic impact drilling tool with self-sustained oscillation pulsed jet is accomplished.