## Petroleum Engineering Equations & Formulas

#### Fluid Pressure

Assuming a normal pressure regime, at a given depth below ground level, a certain pressure must exist
which just balances the overburden pressure (OBP) due to the weight of rock (which forms a matrix) and
fluid (which fills the matrix) overlying this point. The overburden pressure is in fact balanced by a
combination of the fluid pressure in the pore space (FP) and the sress between the rock grains of the
matrix (σ_{g).}

#### Formula:

OBP = FP + σ_{g}Where: σ_{g}: is the stress between the rock grains of the matrix FP: is the fluid pressure in the pore space.

### $$ OBP = FP + \sigma_{g} $$

Where:

- $\sigma_{g}$ is the stress between the rock grains of the matrix.
- $FP$ is the fluid pressure in the pore space.