REAL-TIME DATA LOGGING WHILE DRILLING THROUGH MUD PULSE TELEMETRY
This study investigated the influence of mud channel characteristics on real-time data logging while drilling. Drill string bore filled with flowing mud as the data transmission medium in mud pulse telemetry can have significant changes in its properties as a result of mud type (water-based mud or oil-based mud) which selection depends on the formation being drilled and depth penetrated. Logging data are transmitted to the surface modulated onto pressure pulses which amplitudes are greatly attenuated as drilling depth increases. This attenuation in severe cases can make logging data in the pressure pulse not to be decodable by the transducers. MATLAB Simulink communication blockset was used to model the arrival probability of logging data based on the time of arrival at the surface while drilling using Poisson distribution function. The rate of penetration and data acquisition sample rate were simulated by varying the slope of the ramp function for depth and intensity of data read block for data capture. It was observed that the transmitted pressure pulses propagate to the surface unaffected by depth except in amplitude. Also, lower frequencies were observed to be better carriers of signal in mud pulse telemetry than higher frequencies because attenuation in high frequency components is relatively higher than the low frequency components. It was further discovered that influences of both drilling fluid viscosity and volume fraction of gas in drilling fluids on transmitted pulse amplitude were more notable than that of internal diameter of drillpipe.