Research Of Signal Transmission Characteristics Of Double Flow Drill Pipe

Double drill structure of double flow drill pipe not only had a distinct advantageon the amount of drilling fluids, cleaning of down hole waste, precise control of downhole pressure, safety performance of drilling and efficiency of drilling, but also madesignal transmission in MWD more convenient, signal could be loaded on the doubleflow drill pipe directly, inner drill and outer drill acted as the two lines of transmissionline respectively, and it could achieve wire-transmission in no additional transmissionconductor, is an important direction in the development of MWD.Signal transmission was an important technology in MWD, Therefore, to realizethe MWD in double flow drill pipe, the transmission properties and principle of signalin double flow drill pipe must be known, looking from the structure of double flowdrill pipe, its structure was similar to that of a coaxial cable, so their signaltransmission principle and analysis method were similar.In this paper, first of all, the theory and the circuit method of transmission linewere introduced, because transmission structure of imitation double flow drill pipewas similar to coaxial double’s, coaxial cable was used as the experimental carrier toset up its signal transmission model, provided the basis for signal transmission modeldouble flow drill pipe.Secondly, the imitation double flow drill pipe were machined, which was asame proportion size with actual double flow drill pipe, by measuring imitationdouble flow drill pipe’s line parameters and transmission characteristics, the unitlength in different frequencies were determined, the signal transmission model of3000m imitation double flow drill pipe system was established by using thiscascading model, the signal transmission characteristics was obtained by using theMultisim software to simulate.Then, in order to test the actual signal communication features, the signaltransmission circuit and signal receiving circuit were designed, which were all basedon the principle of power line carrier.2FSK was selected as the signal modulationmethod, AD9832was used to act as the modulation chip. The received signal wasdemodulated by PLL NE564, the demodulation circuit had certain adaptability, toensure normal and stable transmission of signals.Finally, signal transmission model of imitation double flow drill pipe system wasset up, with which signal transmission experiment was done, the way of signaltransmission was one-way. Imitation double flow drill pipe was analyzed for powersupply, DC power supply was selected. Power transmission model of imitation doubleflow drill pipe system was set up, on which signal and DC power were loadedtogether, the power in loader and the effect of signal transmission were observed.