Effects of suspended solid particles on the propagation and attenuation of mud pressure pulses inside drill string

The attenuation of mud pressure pulses in the drilling fluid inside drill string has restricted the application of mud pulse telemetry systems in directional drilling operations. This paper aims to investigate the effects of suspended solid particles on the propagation and attenuation characteristics of pressure pulses. In this work, an analytical model estimating the wave speed and attenuation factor of pressure pulses has been proposed based on the solid–liquid two-fluid model by performing linear perturbation theory, with the interactions of the solid–liquid two phases being considered. The model calculations are compared with the results of the experiments, showing good agreement. Based on the model, the propagation behavior of pressure pulses has been analyzed to ascertain the important parameters affecting the wave speed and attenuation factor. The results indicate that the angular frequency of the pressure pulses, the volume fraction, size and density of the solid particles all exert significant influence on the pressure pulses propagation and attenuation. Lower angular frequency, solid particle size and density tend to reduce the attenuation of pressure pulses. The pressure pulses have maximum attenuation when the volume fraction falls within the range of 20%–30%. For different angular frequencies, the general effects of the volume fraction, size and density of the solid particles on the wave speed and attenuation factor are the same, although they differ in degree.