Stress at edge of wellbore breakout

Input(s)

$\mathrm{C}_{\mathrm{o}}$: Wellbore Strength (psi)

$\mathrm{P}_{\mathrm{p}}$: Pore Pressure $(\mathrm{psi})$

P: Drawdown Differential in Pressure (psi)

$\sigma_{\mathrm{t}}$: Thermally Induced Stress (psi)

$\mathrm{w}_{\mathrm{b}}$: Wellbore Breakout (degrees)

$\mathrm{S}_{\mathrm{hmin}}$: Minimum Horizontal Stress (psi)

Output(s)

$\theta_{\mathrm{b}}$: Breakout Angle (degrees)

$\mathrm{S}_{\mathrm{hmax}}$: Maximum Principle Stress (psi)

Formula(s)

$$ \begin{gathered} 2 \theta_{\mathrm{b}}=\pi-\mathrm{w}_{\mathrm{b}} \\ \mathrm{S}_{\mathrm{h} \max }=\frac{\left(\left(\mathrm{C}_{\mathrm{o}}\right)+2 * \mathrm{P}_{\mathrm{p}}+\mathrm{P}+\sigma_{\mathrm{t}}\right)-\mathrm{S}_{\mathrm{h} \min } *\left(1+2 * \cos \left(\theta_{\mathrm{b}}\right)\right)}{1-2 * \cos \left(\theta_{\mathrm{b}}\right)} \end{gathered} $$

Reference(s)

Mark D. Zoback, Reservoir Geomechanics, Cambridge University Press, UK, Page: 223.