Petrospec Technologies
Overburden Gradient Worksheet
phi = phi
0
* e
(- pde * tvd)
obg = (obg
max
* ( 1.0 - phi ) + nhg * phi ) / tvd
Constants
Constant Name
Value
Kelly Bushing (feet)
Water Depth (feet)
Initial Porosity (decimal)
Normal Hydrostatic Gradient (psi/ft)
Maximum Overburden Gradient (psi/ft)
Porosity Decay Exponent
Slow Porosity Decay = 0.0001
Gulf of Mexico = 0.00025
Fast Porosity Decay = 0.001
Data Values
True Vertical Depth
(feet)
Porosity
(decimal)
Overburden Pressure
(psi)
Overburden Gradient
(psi/ft)
