Experimental Study on Acoustic Propagation Characteristics in Drill-String

The acoustic transmission technology of information measured by MWD is an important research direction of underground information wireless transmission technology. The drill string as information transmission channel is composed by size difference drill pipe, so it is one of important issue to understand the relationship between the drill pipe size difference and acoustic wave propagation characteristics in the drill-string. That is related to the selected acoustic carrier and detection. A test device for testing the drill string acoustic propagation characteristics was established. Test and analysis of acoustic wave propagation characteristics in drill string which consisting by size differences drill pipe. The results showed that: When the drill size differences exist, the acoustic propagation characteristics in drill string have changed, performance in the number of the pass-band was reduces, some of the pass-band disappearance, and the pass-band width is narrowed, When acoustic waves through the drill string composition by size differences drill pipe, the attenuation is larger than the cyclical one, Less affected by differences in the drill pipe size is the low-frequency pass band acoustic waves, There is a separate arrangement, the effect can be reduced.