Real-Time Data Logging While Drilling Through Mud Pulse Telemetry

ABSTRACT

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 (waterbased

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.