The Research And Development Of MWD Data Acoustic Transmission Technology Based On Drill Pipe

To solve the problems of MWD data transmission effectively in air drilling and foam drilling, the thesis studied the several key techniques of MWD data acoustic transmission technology based on drill pipe, including the research on the transmission characteristics of acoustic wave in the drill pipe, the development of the transducer used to emit acoustic wave in the down hole, the research on acoustic wave transmission method and the design of circuit used to control acoustic wave emission.First of all, in order to study the transmission characteristics of acoustic wave in the drill pipe, the vibration generator and homemade excitation device were used as the excitation source, the special drill pipe was used as transmission signal path, the experiment was done to test the drill pipe's acoustic wave transmission characteristics in the laboratory under the different conditions. The structural features of the drill pipe and the acoustic type and characteristics in the drill pipe were analyzed in detail, the carrier type and factors were determined which affected the acoustic transmission characteristics. The band characteristics and dispersion properties of acoustic wave of different frequencies in different lengths of drill pipe were analyzed, the frequency characteristics and attenuation of acoustic wave transmission in the drill pipe were determined. Based on these results, factors were analyzed which affected the acoustic transmission characteristics, the carrier optimal frequencies were determined. The research and conclusion provided the basis and guidance for the design of the suitable acoustic emission transducer and the data transmission mode.Then according to the conclusions of the experiment, considering the small down hole space and high temperature and pressure and the difficult power supply, the principle and structure of low-frequency acoustic emission transducer were analyzed on the active service. The electric ceramic transducer and the rare earth giant magnetostrictive transducer were designed and developed which adapted to down hole harsh environment, the emission capability, manufacture level and size magnitude were compared between the electric ceramic transducer and the rare earth giant magnetostrictive transducer. Considering difficult power situation of acoustic emission transducer, the design of horn structure was proposed to use to amplify acoustic emission energy. Considering the very limited down hole installation space, slotted in the drill collar and made measurement short pipe nipple method were proposed.At last, combined with the characteristics of drill pipe channel and down hole data, the thesis adopted 2FSK method to modulate WMD data and used data error control positive and negative code methods. Aimed at the high temperature environment in the down hole, the military chip was used as the control chip in the design of circuit which controlled acoustic wave emission transducer, the controlling circuit structure and launched process were designed. Besides all, the selection of down hole power was studied.