Radiation pattern and seismic waves generated by a working roller‐cone drill bit

Abstract

The seismic body wave radiation pattern of a working roller-cone drill bit can be characterized by theoretical modeling and field data examples. Our model of drill-bit signal generation is a pseudo-random series of bit-tooth impacts that create both axial forces and tangential torques about the borehole axis. Each drill tooth impact creates an extensional wave that travels up the drill string and body waves that radiate into the earth. The model predicts that P-waves radiate primarily along the axis of the borehole, and shear waves radiate primarily perpendicular to the borehole axis. In a vertical hole, the largest P-waves will be recorded directly above and below the drill bit; whereas, the largest shear waves will be recorded in a horizontal plane containing the drill bit. In a deviated borehole, the radiation patterns should be rotated by the inclination angle of the drill bit. This proposed seismic body wave radiation pattern is investigated with field data examples.

The use of monopole and dipole sources in crosswell surveying

“…An additional pulse is also visible, particularly for z=30.0 m. This mode can be identified as a result of the propagation of conical waves (Meredith et al, 1993;Samec, 1991, Rector andHardage, 1992). This wave is the three-dimensional, axisymmetric space equivalent of a two-dimensional head-wave.…”

The use of monopole and dipole sources in crosswell surveying

“…An additional pulse is also visible, particularly for z=30.0 m. This mode can be identified as a result of the propagation of conical waves (Meredith et al, 1993;Samec, 1991, Rector andHardage, 1992). This wave is the three-dimensional, axisymmetric space equivalent of a two-dimensional head-wave.…”

Estimating rock properties using sound levels produced during drilling

“…A couple of studies in oil and gas industries have proposed a technique called ''Seismic While Drilling'' for estimating rock formations. For instance, few studies have proposed the use of noise produced by the bit during drilling as a seismic source for surveying the area around a well and also for formation characterization while drilling [5][6][7][8][9][10][11][12][13][14]. A recent study [15] has also reported a method of estimating formation properties by analyzing acoustic waves that are emitted from and received by a bottom hole assembly.…”