DIPOLE FLEXURAL WAVES SPLITTING INDUCED BY BOREHOLE PRESSURIZATION AND FORMATION STRESS CONCENTRATION
井孔压力与地层应力集中诱导的偶极弯曲波的分裂

Based on the theory of acoustoelasticity, which is concerned with small deformation superimposed upon large initial strain, we numerically calculate the Stoneley and flexural mode dispersion curves in a fluid-filled borehole which is pressurized by fluid and uniaxially stressed solid formation. Computational results show that the fractional changes in the phase velocity are most sensitive to frequency sensitivity coefficient C m_2 , C m_3 and C m_4 , corresponding to three third-order elastic constant c_ 111 , c_ 112 and c_ 123 , respectively, for formations with higher degree of nonlinearity. The results also indicate that the velocity increases at the crossover point of dispersion curves for both flexural waves polarized parallel and perpendicular to the stress direction along with borehole pressure increase.