The Structural Design Of MWD Acoustic Telemetry System Of Oil And Gas Wells

The acoustic telemetry while drilling is a wireless transmission technology which use acoustic as carrier, which transmits borehole information to the ground in the drilling process. It may also transmit information from ground to borehole, so as to realize the borehole and ground bidirectional communications. The acoustic telemetry while drilling is a relatively new wireless transmission technique. The acoustic telemetry while drilling has the advantage of low cost, small size, fast transmission speed, a relatively large amount of data volume, free from the impact of formation properties. The acoustic transmission disadvantage is acoustic transmission method not only in connection with the drill pipe structure of its periodic, but is very sensitive to the channel damping. The signal attenuation will be serious when the sound wave is propagating along the drill string. The acoustic transmission is susceptible to ambient noise in the drilling environment.In order to realize downhole acoustic telemetry in oil and gas well by using longitudinal wave as an information transmission carrier, sound wave transmission rule in drillpipe as the information transmission channel was studied. Alternation of pass-band and stop-band, structure of CIC filter and forming mechanisms of pass-band accompanied by resonance peak were discussed. The influence of transverse plane, the length of drill pipe and cross section of coupling interpolation on distribution of pass-band and stop-band were analyzed. Damping effect of drilling fluid, radial radiation and viscoelastic formation were also analyzed. The carrier frequency, pulse form and number were optimized. Based on analysis of parameters'requirements of the acoustic transducer which are suitable for down-hole signal transmission, this paper studied the structure, acoustic matching and circuit matching of the transducer and acoustic transducer location in the drill channel was designed. Mechanical structure design is the premise and foundation of the acoustic telemetry system while drilling realizing measuring function.Its mechanical parts is shell structure of the acoustic telemetry system while drilling, providing inclusive space for transducer, sensor and circuit. Therefore, the structure and strength of design is reasonable related to the telemetry system's security and measurement stability. As part of the drill string, downhole launch short joint must be to maintain sufficient strength and corrosion resistance in the high temperature and pressure environment, but also provide a good seal between instrument capsule and drill fluid. The structural of transmitting part and receiving part in acoustic telemetry system were systemic designed in the paper. This paper designed several kinds of acoustic telemetry system suitable for drilling environment. The optimal design scheme can be chosen and strength calculation was verified.