METHOD AND APPARATUS FOR LASER-BASED NON-CONTACT THREE-DIMENSIONAL BOREHOLE STRESS MEASUREMENT AND PRISTINE STRESS ESTIMATION

摘要

A method and apparatus for non-destructively determining borehole stress parameters, that measures acoustic velocities in the rock formation. The apparatus or laser ultrasonic apparatus involving an acoustic signal generator and at least one interferometer sensing unit with shared reference is used to perform non-contact measurement. Horizontal and vertical stresses are evaluated in more than three angular directions (sometimes called azimuths) around the axis of the borehole using acoustoelastic principle. The magnitudes and directions of principal pristine stresses in the rock formation are derived from the measurement data by using closed-form solutions. Magnetometer is used to determine the angular direction of the stress measurement.