Pore pressure increase due to fluid activity (Mody and Hale)

Input(s)

$E_{m}$: Membrane Efficiency (dimensionless)

R: Gas Constant (psi/mol K)

T: Temperature $(\mathrm{K})$

$\mathrm{V}$: Volume $\left(\mathrm{ft}^{3}\right)$

$A_{p}$: Pore Fluid Activity (dimensionless)

$A_{m}$: Mud Activity (dimensionless)

Output(s)

$\delta P$: Pore Pressure Increase $(\mathrm{psi})$

Formula(s)

$$ \delta P=\mathrm{E}_{\mathrm{m}} *\left(\frac{\mathrm{R} * \mathrm{~T}}{\mathrm{~V}}\right) * \ln \left(\frac{\mathrm{A}_{\mathrm{p}}}{\mathrm{A}_{\mathrm{m}}}\right) $$

Reference(s)

Mark D. Zoback, Reservoir Geomechanics, Cambridge University Press, UK, Page: 321.