| With the development of oil and gas exploration technology and growing of deep and ultra-deep well number, how to improve low-speed in deep drilling has become a problem. Hold-down effect which affects drilling speed is a major factor. Pulse jet can reduce bottom-hole pressure and overcome hold-down effect.Based on the investigation and analysis of the mechanism of hydraulic pulse modulators, using jet dynamics to design piston-spool modulator physical model, this paper has studied modulator vibration characteristics with methods of mathematical computation mathematical simulation and laboratory experiment, then examine the influence of the modulator’s hydraulic parameters, the upstream pressure ‘P’ and drilling fluid flow ‘Q’ et al, and structure parameters, valve cover, valve core and valve lift et al, on pulse frequency and inferior vena stress amplitude. With the increase of riser pressure ‘P’ and drilling fluid flow ‘Q’, the vibration frequency of the modulator linear increases.Through mechanical processing and indoor experiment, this paper has verified the feasibility of modulator, and found that the negative pressure amplitude can reach 2.0~4.38 MPa.When down- hole hydraulic shock occurs, internal pressure fluctuations propagate to upstream direction, which causes devastating effects. Based on the theory of the self-excited oscillation cavity and muffler, pressure wave back propagation damping model is researched. Using Fluent Simulation Method, this paper has found out the influence of cavity length, lumen diameter, tube and the pipe head and exit diameter ratio change to lower outlet pressure amplitude. Study its reducing mechanism through the analysis of interior cavity flow field changes. When the ratio of inlet diameter to the outlet diameter is 1.2:1, the ratio of inner tube to cavity length is 2:3, reducing pressure amplitude has lead a good effect. The research has provided a support for the carrying out of pulse jet and reverse pressure wave propagation. |
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