Acoustoelasticity theory, numerical analysis and practical example of the cased hole with stress concentration by cross-dipole acoustic logging

作者：Li G^*; Wang KX; Liu JX; Cao ZL; Lu WG; Xie RH; Liu JS; Lu XM

来源：Chinese Journal of Geophysics, 2006, 49(1): 295-304.

• cased hole
• stress concentration
• acoustoelasticity
• flexural waves splitting
• dispersion curves crossover

In view of actual cases that most of damaged oil wells under the action of abnormal formation stress are all for cased hole, through solving distributions of stress fields around the well in each layers caused by stress concentration of borehole and utilizing perturbation integral method, acoustoelastical equations only for the open hole are developed into the cases of being suitable to eased hole. Under the action of biaxial stress, sensitivity coefficients and velocity-stress coefficient in acoustoclastical equations and dispersion curves of two dipole flexural modes polarized parallel and perpendicular to the applied stress direction are numerically investigated, respectively. Results show that velocity-stress coefficients primarily depend on the formation parameters, specially, the terms including third-elastic modulus in acoustoelastical equations; the split of phase velocities of flexural modes with different polarization and crossover of their dispersion curves are still main characteristics of the formation anisotropy induced by stress for cased hole, but usually dispersion curves will be moved to the higher frequency region, especially for lower velocity formation, which is a difference for cased hole from the case in open hole. This put forward new requirements to carry out forward and inverse operations in the cased hole case. A practical example of field data processing for a cased hole is also presented, which is in basic agreement with theoretical predict.

• 出版日期2006-1
• 单位吉林大学