Wireless MWD Continuous Wave Signal Transfer Model and Simulation

Abstract

Through studying the transportation and vibration of drilling pressure fluctuation in drill stem, mathematical models between pressure flow and time distance are established, the differential equations corresponding to the above-mentioned variables are deduced and general solutions of differential equations are obtained. By analyzing the transferring mode of power transmission signals and describing the influence of drill stem on fluctuation through characteristic impedance and transmittance, the expression of frequency domain hydraulic head and frequency domain flow is given. Through model-simulation, pressure distribution of different signals along drill stem are calculated, which shows, in the process of transferring signals, the pressure wave of drill stem is in the form of standing waves. The influences of different signal terminal impedances and characteristic impedances on signal transfer are analyzed, simulation analysis of the signal of different frequency inside the drill stem is made, and the attenuations of different frequency inside the drill stem are obtained. Through calculating the natural frequency of drill stem, the methods for seeking out the apposite frequency of transmitted signal suitable for data transfer in the drilling stem, which theoretically supports the frequency selection of continuous-wave communication technology.