Numerical Simulation The Wave Fields Of Multipole Acoustic Logging-While-Drilling In Complex Borehole

With the wide application of LWD technology,more and more study on wave propagation characteristics of multipole acoustic logging-while-drilling had been achived.At present,the main research direction of propagation characteristics of wave propagation characteristics of multipole acoustic logging-while-drilling in complex borehole and the anisotropic medium.This paper aims to research influence on wave propagation characteristics of multipole acoustic logging-while-drilling under the conditions of complex borehole.How the borehole environment impact mode wave frequency dispersion characteristics.These researches are important for data analyses.The results were firstly carried out by using the software system of Comsol Multiphysics.We compared our results with the analytical solutions and found that they are in quantitative agreement.This paper evaluates the wave propagation characteristics of multipole acoustic logging-while-drilling using low-frequency dipole and quadrupole acoustic sources.The numerical modeling results show that the LWD dipole acoustic waves contain strong tool waves traveling along the collar.In comparison,the quadrupole wave is a better measurement candidate.Wave propagation characteristics in the circular borehole generated by dipole acoustic sources,simulation results shows as the increasing of the distance between the tool and the central axis,the first wave travelling time becomes longer,and amplitude of the wave also becomes larger.Wave propagation characteristics in the circular borehole generated by quadrupole acoustic sources,simulation results shows as the increasing of the distance between the tool and the central axis,the first wave travelling time becomes shorter,and amplitude of the wave also becomes larger.Wave propagation characteristics in the elliptical borehole generated by dipole acoustic sources,simulation results shows as the increasing of the distance between the tool and the central axis,the first wave travelling time becomes longer,and amplitude of the wave also becomes larger.As the increasing of the ellipse eccentricity,the first wave travelling time becomes shorter,and amplitude of the wave also becomes larger.As the increase of the inclination angle,the first wave travelling time becomes longer,and amplitude of the wave also becomes small.Wave propagation characteristics in the elliptical borehole generated by quadrupole acoustic sources,simulation results shows as the increasing of the distance between the tool and the central axis,the first wave travelling time becomes shorter,and amplitude of the wave also becomes larger.As the increasing of the ellipse eccentricity,the first wave travelling time becomes shorter,and amplitude of the wave also becomes larger.