Rotation of maximum principal stress near wellbore (Zoback \ Day-Lewis)

Input(s)

A: Constant a Value (dimensionless)

$\Delta$: Fault Orientation (degrees)

q: Ratio of Pore Pressure to Differential Stress (dimensionless)

Output(s)

$\gamma$: Stress Rotation (radian)

Formula(s)

$$ \gamma=0.5 * \operatorname{atan}\left(\mathrm{A} * \mathrm{q} * \frac{\sin (2 * \Delta)}{1+\mathrm{A} * \mathrm{q} * \cos (2 * \Delta)}\right) $$

Reference(s)

Mark D. Zoback, Reservoir Geomechanics, Cambridge University Press, UK, Page: 393.