In-situ stress determination by stress perturbation

The normal borehole deformation meter is used to measure the radial deformations of borehole induced by stress perturbation, as which is taken here the normal stress-relief overcoring technique. For the cases with and without knowledge of material parameters, the induced deformations of borehole are computed with different methods and compared with measured ones. In this way, the three dimensional in-situ stresses can be determined uniquely for actual complicated geological conditions and only one borehole is needed.