Geomechanics and FracturingIn-Situ Stress and Rock Mechanics

Pore Pressure of Shale Traugott Formula

P_{psh}=z\left[\frac{S_v}{z}-\left(\frac{S_v}{z}-\frac{P_{hydro}}{z}\right)\left(\frac{R_o}{R_n}\right)^{1.2}\right]

Pore Pressure of Shale Traugott calculates shale pore pressure for in-situ stress and rock mechanics workflows in geomechanics and fracturing.

Calculate

How engineers use this formula

Use this formula when the listed inputs (z, S_v, R_o, R_n, P_hydro) are known and the assumptions behind the cited in-situ stress and rock mechanics relationship match the engineering case being checked.

Assumptions

Input values are representative for the well, reservoir, fluid, or equipment case being evaluated.
The declared units match the field-unit constants used in the formula.
The cited formula applies to the selected petroleum engineering workflow.

Limitations

The calculation does not replace a full engineering model or operating procedure.
Accuracy depends on the source correlation, assumptions, input quality, and unit consistency.

Common mistakes

Mixing unit systems without converting the inputs.
Using default example values as field recommendations.
Applying the formula outside the source assumptions.

Default example

Using the default inputs, P_psh equals 7,106.552525 psi.

zft

10000

S_vpsi

9000

R_oohm-ft

1.5

R_nohm-ft

P_hydropsi

4650

Inputs

z

Depth

S_v

psi

Vertical Stress

R_o

ohm-ft

Observed Shale Resistivity

R_n

ohm-ft

Expected Normal Shale Resistivity

P_hydro

psi

Hydrostatic Pore Pressure

Outputs

P_psh

psi

Shale Pore Pressure

S_v

psi

Vertical Stress

P_hydro

psi

Hydrostatic Pore Pressure

R_o

ohm-ft

Observed Shale Resistivity

R_n

ohm-ft

Expected Normal Shale Resistivity

Source and review

reviewed

Reservoir Geomechanics, Zoback, M.D. (2007)

Zoback, M.D. 2007. Reservoir Geomechanics. Cambridge University Press, Page 47.

Source