Patent ID: 7463550

Claim:
A method of estimating horizontal shear modulus c 66 in an anisotropic formation with a vertical X 3 -axis surrounding a borehole, comprising: measuring Stoneley dispersion with an acoustic tool; and calculating a horizontal shear modulus c 66 from the measured Stoneley dispersion using a process that accounts for both the presence of the acoustic tool in the borehole and near-wellbore alteration effects, the process including: attributing heavy-fluid column properties to the tool; determining far-field formation compressional velocity; estimating formation shear modulus c 66 using measured Stoneley velocity; calculating a reference shear velocity for an equivalent isotropic formation; determining heavy-fluid compressional velocity as a function of formation compressional velocity; calculating a reference Stoneley dispersion and associated eigenfunctions for an assumed homogeneous and equivalent isotropic formation; determining Stoneley wave velocity at a plurality of frequencies at each depth level of interest; creating measured Stoneley dispersion data at each depth level of interest; comparing measured Stoneley dispersion at a selected depth with the reference Stoneley dispersion; if a difference exists between the measured and reference Stoneley dispersions, selecting a plurality of Stoneley velocity data sets at the plurality of frequencies from the measured Stoneley dispersion; and calculating the radial profile of the horizontal shear modulus c 66 from the measured Stoneley dispersion data.