Design Of Split Vibrational Friction-reducing Generator

Complex structural Wells such as extended reach wells and horizontal wells have become an important means for the exploration and development of complex oil and gas reservoirs.During complex structure well drilling,the conventional screw+MWD drilling mode has shortages,rate of penetration is limited.Hydraulic oscillator(Agitator)is one of the effective ways to solve this problem,but effective scope of one single tool is limited,more than one tools would consume a lot of water power.according to this situation,this paper puts forward the idea of split vibrational friction-reducing generator.Firstly,based on the theory of vibration reduction,by considering vibration of drill string and friction coupling,a mathematical model of drill string axial vibration is established,the effect of vibration amplitude and frequency on friction reduction is analyzed with one point vibration.The results show that compared with frequence,the change of amplitude is more conducive to friction reduction.Then the law of pressure pulse attenuation is studied,the results show that the attenuation rate of amplitude is accelerated with the increase of frequency.On this basis,the optimization criteria of high amplitude and low frequency are establishedThen,the split vibrational friction-reducing generator is designed,it consist two parts,the upper axial vibrators and the lowwer rotor pulse generator.Using the moving grid technology to simulate rotor sub work principle analysis,the results show that it can produce a relatively ideal pressure pulse.Based on this,the dish spring is designed used in 127 mm tool.Finally,the influence of mass flow rate and structural parameters on pressure pulse characteristics are studied,the structural parameters contain: gap between rotor and stator,rotor diameter,flow diameter,helix Angle.The results show that: with the increase of gap,amplitude,frequency and pressure decrease;with the increase of flow diameter,amplitude,frequency and pressure loss are reduced,with the increase of rotor diameter,amplitude,frequency decrease and pressure increase;helix angel has little effect.On this basis,selecting suitable structure parameters expand orthogonal test,determine the optimum structural parameters according to the criterion of high amplitude and low frequency.The split vibrational friction-reducing generator provides a new technical means for friction reduction,it has great significance of improving the efficiency of complex reservoir and reducing drilling cost is of great significance.