We investigate the feasibility of estimating an in situ three-dimensional stress field by using data of drilling-induced tensile fractures (DTFs) observed in a single borehole. The principal assumptions in this investigation are that the rock is isotropic, homogeneous and elastic. A DTF is a longitudinal crack consisting of many small parallel cracks which are oblique to the borehole axis. A DTF is characterized by its circumferential position (θmD) along the borehole surface and the inclination (γm) of the small cracks with respect to the borehole axis. We show how it is possible to estimate the three-dimensional stress field by using the variation of ΘmD and γm with respect to borehole orientation (i.e. azimuth and inclination of a borehole). Based on the variation of ΘmD and γm as functions of borehole orientation which changes with depth, an inverse problem is formulated to estimate the three-dimensional stress field. Tests with synthetic data sets (ΘmD and γm) show that it is feasible to estimate the three-dimensional stress field and that the statistical approach is appropriate for the inversion practically. Finally, we discuss a DTF data set (ΘmD and γm) measured in a real borehole in the northern area of Japan Main Island and apply the inversion technique to estimate the stress field.
|Number of pages||12|
|Journal||International Journal of Rock Mechanics and Mining Sciences|
|Publication status||Published - 1998 Jan 1|
ASJC Scopus subject areas
- Geotechnical Engineering and Engineering Geology