Patent ID: 7513167

Claim:
A method for determining the stress state and material properties in underground media surrounding a borehole, comprising the steps of: first, placing an expandable probe having a single-fracture probe orientation into said borehole at a specific depth of measurement; second, setting the single-fracture orientation of the probe normal to a stress vector to be measured; third, expanding said probe with increasing fluid loading pressure to initiate a single-fracture plane, while simultaneously measuring the diametrical expansion of the probe and the fluid loading pressure; fourth, reducing the fluid loading pressure to zero, then reapplying the loading pressure to reopen the single-fracture plane; fifth, obtaining the pressure versus diametrical expansion (p-d) diagram from the third and fourth steps; sixth, calculating material properties from the p-d diagram by tracking on the diagram; seventh, calculating the stress conditions from the p-d diagrams; further including the step of providing a pair of high friction hemi-cylindrical shells secured to the outer surface of the expandable probe to create a maximum saturated friction effect on the borehole boundary for accurate measurement of individual stress vectors, each shell comprising a unitary component of high strength material, said shells having confronting longitudinal edges that extend generally in a datum plane that corresponds to said single-fracture orientation.