Channel Characteristics of Acoustic Telemetry while Drilling

In order to provide theoretical and experimental basis for the design of acoustic telemetry system,we studied the channel characteristics of acoustic wave transmitting through the drill string.According to the principles of sound wave propagation in periodic structures,this paper adopted numerical simulation technology to perform analysis on sound waves propagating along drill string,the effects of drill string structure,drill string length and drill pipe length on unit impulse response were analyzed.According to the experimental study on 88.9 and 127.0 mm drill pipes,the effects of drill pipe length,supporting means,signal receiving location,drill string curvature and drill string size were investigated.The results show that:drill string channels take on comb-filtering characteristics,which does not vary from the support form significantly;increase in the number of drill pipes leads to time domain waveform attenuation;the channel characteristic is basically not affected by the length of the drill string,but the difference in one drill pipe would cause the narrowing in width of pass band;the positions and width of pass band of different receiving positions are exactly the same,but different in amplitude;drill string curvature has no impact on the pass band position,but would affect its width;drill string size has little effect on the pass band.The simulation and experimental results can provide bases for the design of acoustic telemetry system.