Study Of A New Sound Source On MWD Drilling Acoustic Telemetry

the acoustic transmission technology is used more and more in the field of steerable drilling technology.However,there are many problems such as lack of sound power and limited transmission distance when using the traditional acoustic source.In this paper,the plasma acoustic source is used as a new type of LWD acoustic source.The plasma acoustic source use the principle of underwater acoustic pulse generated by high voltage discharge to transfer acoustic energy,which has high sound pressure level,covering a wide spectrum,high repetition rate,good safety,to achieve large-capacity,long-distance,real-time and fast delivery with down hole information in the strong interference of the drilling.In this paper,the following three aspects of plasma acoustic source are studied:(1)The main structure of the plasma source is analyzed.In view of the complex underground environment,combined with the discharge conditions of sound source,The article conducted investigation and feasibility analysis of the sound source;then it studies the selection of the main components of the high voltage charging system and the high pressure discharge system,including high voltage storage capacitor,step-up transformer,pulse triggering switch,transmission cable,discharge electrode and device which is used to gather energy.(2)Based on the numerical simulation software LS-DYNA,the numerical simulation of the near field propagation law and the law of the energy concentration of the sound field are carried out.The numerical simulation of the evolution of the shock wave surface in the propagation process is carried out,and then the numerical simulation of the energy concentration of the shock wave in the ellipsoidal device and parabolic device is studied using the water discharge shock wave generated by the cylindrical explosive driving source.(3)The pulse discharge circuit and the discharge gap arc resistance are theoretically analyzed.The electrical parameters of the discharge circuit are studied,and the influence of different parameters on the acoustic pulse wave is tested.