Axial stress around vertical wellbore
Input(s)
R: Radius of Wellbore (ft)
\(\mathrm{r}\): Position in Respect to Centre of Wellbore (ft)
\(\Theta\): Azimuth of \(\mathrm{S}_{\mathrm{hmax}}(\mathrm{rad})\)
\(\mathrm{S}_{\mathrm{hmax}}\): Maximum Horizontal Stress (psi)
\(\mathrm{S}_{\mathrm{hmin}}\): Minimum Horizontal Stress (psi)
Output(s)
\(\tau\): Twisting Stress (psi)
Formula(s)
\[
\tau=0.5 *\left(\mathrm{~S}_{\mathrm{h} \max }-\mathrm{S}_{\mathrm{h} \min }\right) *\left(1+\left(\frac{2 * \mathrm{R}^{2}}{\mathrm{r}^{2}}\right)-\left(\frac{3 * \mathrm{R}^{4}}{\mathrm{r}^{4}}\right)\right) * \sin (2 * \Theta)
\]
Reference(s)
Mark D. Zoback, Reservoir Geomechanics, Cambridge University Press, UK, Page: 170.