Geomechanics and FracturingIn-Situ Stress and Rock Mechanics

Linearized Mohr-Coulomb Criteria Formula

\sigma_1=C_o+(\sqrt{\mu^2+1}+\mu)^2\sigma_c

Linearized Mohr-Coulomb Criteria calculates maximum effective principal stress 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 (C_o, mu, sigma_c) 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, sigma_1 equals 11,858.285364 psi.

C_opsi

2500

mudimensionless

0.6

sigma_cpsi

3000

Inputs

C_o

psi

Unconfined Compressive Strength of Rock

mu

dimensionless

Slope of Failure Line

sigma_c

psi

Minimum Effective Principal Stress

Outputs

sigma_1

psi

Maximum Effective Principal Stress

C_o

psi

Unconfined Compressive Strength of Rock

sigma_c

psi

Minimum Effective Principal Stress

mu

dimensionless

Slope of Failure Line

Source and review

reviewed

Zoback, M.D. 2007. Reservoir Geomechanics, Cambridge University Press, Page 93.

Source