Circumferential Stresses and Crack Opening Displacements at a Fractured Well Bore

摘要

Results of a plane strain analysis of the circumferential stresses around the wall of a fractured borehole and the associated crack opening displacements are presented. These borehole stresses are of considerable interest in at least two geologic applications involving the possibility of forming multiple fractures at boreholes and the measurement of in-situ stresses. For short cracks, the borehole stresses near the crack are shown to become highly compressive over a large region of the borehole. As the crack grows, the magnitude of this stress decreases but remains compressive over a larger angle around the borehole. These fracture induced stresses effectively clamp the borehole in compression and prohibit additional crack initiation and growth under quasi-static loading conditions. It it also clear that these compressive stresses and associated strains must be accounted for in any stress-relieving technique utilized for the investigation of in-situ stresses. (ERA citation 06:033932)