Method for estimating formation in-situ stress magnitudes using a sonic borehole tool

摘要

A method of estimating formation in-situ stress magnitude and nonlinear constants of an earth formation traversed by a borehole includes analyzing the flexural wave dispersions for dipole sources aligned parallel and perpendicular to the maximum far-field compressive stress direction together with the Stoneley wave dispersion derived from a monopole source. In the presence of formation and borehole stresses above and beyond those in an assumed isotropic reference state, the borehole flexural and Stoneley wave velocity dispersions are also functions of the formation stresses and nonlinear constants. A multi- frequency inversion of the flexural or Stoneley wave velocity dispersions over a selected frequency band is performed to determine the uniaxial stress magnitude S and the quantities ##EQU1## where c.sub.111, c.sub.112, and c.sub.123 are the formation non-linear constants.