Patent ID: 8944183
Filing Date: 2015-02-03
Classification: E21B,G01V

Abstract:
1. An apparatus configured to evaluate an earth formation, the apparatus comprising: a bottomhole assembly (BHA) configured to be conveyed in a borehole; a drillbit on the BHA configured to generate an acoustic signal including multipole components propagating through the earth formation during continued rotation of the BHA; a drill collar on the BHA coupled to the drillbit, wherein the drillbit and drill collar are configured, when rotating at a frequency in a predetermined frequency band, to generate multipole components propagating through the earth formation substantially free of multipole components propagating through the drill collar; a first acoustic detector on the BHA configured to produce a first signal indicative of the multipole components contained in the propagating acoustic signal; a second acoustic detector on the BHA axially spaced apart from the first acoustic detector and configured to produce a second signal indicative of the multipole components contained in the propagating acoustic signal; and at least one processor configured to estimate a formation velocity of the earth formation using the first signal and the second signal.