Geomechanics and FracturingIn-Situ Stress and Rock Mechanics

Mode I Fracture Stress Intensity Formula

K_I=(P_f-S_c)\pi L^{0.5}

Mode I Fracture Stress Intensity calculates mode i stress intensity 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 (P_f, S_c, L) 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, K_I equals 23,561.944902 psi*ft^0.5.

P_fpsi

6500

S_cpsi

5000

Lft

Inputs

P_f

psi

Fracture Pressure

S_c

psi

Minimum Principal Stress

L

Fracture Length

Outputs

K_I

psi*ft^0.5

Mode I Stress Intensity

P_f

psi

Fracture Pressure

S_c

psi

Minimum Principal Stress

L

Fracture Length

Source and review

reviewed

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

Zoback, M.D. 2007. Reservoir Geomechanics, Cambridge University Press, Page 122.

Source