Definition - What does Normal Pressure mean?
Normal Pressure, also known as normal pore pressure is the pressure of a formation fluid that is considered normal in an area where a change in pressure per unit depth is equal to hydrostatic pressure. The formation fluid may be gas, oil or water but the pressure of the fluid will be equivalent to the normal pressure, i.e., the hydrostatic head of a water column.
Petropedia explains Normal Pressure
Once the normal pressure of an area is known, one can estimate the normal pressure gradient because it is expressed in terms of pressure per unit length. With the help of pressure gradient, geologists can easily estimate the rate of pressure change with depth and direction. As the depth of a borehole increases the pressure also increases which signifies that as we go down the earth's surface, the pressure is expected to increase. 9.792 kPa/m is the measure of the normal hydrostatic pressure gradient for fresh water. The normal pressure is expressed in Pascals or Kilopascals whereas the normal pressure gradient is generally expressed in psi/ft or kPA/m (kPA = kilo Pascals).