Stress at edge of wellbore breakout

Input(s)

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

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

P: Drawdown Differential in Pressure (psi)

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

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

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

Output(s)

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

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

Formula(s)

2θb=πwbShmax=((Co)+2Pp+P+σt)Shmin(1+2cos(θb))12cos(θb)\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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