Drilling EngineeringWell Control
Pore Pressure Gradient - Zamora Formula
Pore Pressure Gradient - Zamora calculates pore pressure gradient for well control workflows in drilling engineering.
How engineers use this formula
Use this formula when the listed inputs (g_n, d_cn, d_co) are known and the assumptions behind the cited well control 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, g_p equals 0.591818 psi/ft.
g_npsi/ft
0.465
d_cndimensionless
1.4
d_codimensionless
1.1
Inputs
g_n
psi/ftNormal Pore Pressure Gradient
d_cn
dimensionlessNormal Corrected d-Exponent
d_co
dimensionlessObserved Corrected d-Exponent
Outputs
g_p
psi/ft
Pore Pressure Gradient
g_n
psi/ft
Normal Pore Pressure Gradient
d_cn
dimensionless
Normal Corrected d-Exponent
d_co
dimensionless
Observed Corrected d-Exponent
Source and review
reviewedAdvanced Well Control, Watson, D., Brittenham, T., Moore, P.L. (2003)
Watson, D., Brittenham, T. and Moore, P.L. 2003. Advanced Well Control, SPE Textbook Series Vol. 10, Page 52.
Source