Geomechanics and FracturingIn-Situ Stress and Rock Mechanics

Fracture Pressure - Hubbert and Willis Formula

S_{hmin}=0.3(S_v-P_p)+P_p

Fracture Pressure - Hubbert and Willis calculates fracture pressure or minimum horizontal 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 (S_v, P_p) 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, S_hmin equals 4,850 psi.

S_vpsi

8000

P_ppsi

3500

Inputs

S_v

psi

Vertical Stress

P_p

psi

Pore Pressure

Outputs

S_hmin

psi

Fracture Pressure or Minimum Horizontal Stress

S_v

psi

Vertical Stress

P_p

psi

Pore Pressure

Source and review

reviewed

Zoback, M.D. Reservoir Geomechanics. Cambridge University Press, Page 281.

Source