Acoustic velocity of seismic-while-drilling (SWD) borehole guided waves

Borehole guided waves, other than the extensional waves traveling through the drillstring, can be used as pilot signals to obtain seismic-while-drilling (SWD) seismograms and information about the drilling conditions. This occurs when there is no rotation of the drillstring while drilling and when the contacts between the drillpipe and the borehole wall preclude the propagation of the extensional wave. To obtain the velocity of the guided waves, we model the compressional-wave velocity of drilling mud with different compositions of low-and high-gravity solids, corresponding to a given drilling plan and taking into account the presence of formation cuttings and in-situ conditions. Then we compute the velocities of the tube wave (with and without casing) and the guided wave traveling in the mud inside the drillstring (pipe wave). The results indicate the pipe wave constitutes a reliable pilot signal in the absence of drillpipe rotation. This allows us to obtain a complete depth reverse vertical seismic profile.