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.

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