ABSTRACT
Advancements in wellbore imaging technologies allow observations of very small-scale features on the borehole wall such as drilling-induced tensile wall fractures which occur only in the rock immediately adjacent to the borehole wall due to the stress concentration. We utilize an interactive software system, SFIB (Stress and Failure of Inclined Boreholes, Peška & Zoback 1997a), to demonstrate how the formation of drilling-induced tensile wall fractures is controlled by the in situ stress and is supported by drilling perturbations related to excess mud weight and borehole cooling. The calculations also illustrate various shapes of drilling-induced tensile fractures under different stress conditions and borehole directions. Relationship between the stress and fractures can be used to constrain the in situ stress which is essential for wellbore stability and hydrocarbon migration. We present a method for stress determination from drilling- induced tensile fractures detected by image data at various depths in multiple variably-oriented wellbores.
