Definition - What does Osmotic Pressure mean?
Osmotic Pressure is the minimum amount of pressure that is applied on a solution to stop the inward flow of a liquid such as water across a semipermeable membrane. At times osmotic pressure is the measure of the tendency to absorb water back into any solution because of osmosis process. A good example of an osmotic system is a hydrocarbon reservoir.
Petropedia explains Osmotic Pressure
In any osmotic system such as reservoirs, there are low salinity regions and high salinity regions. When areas with both low and high salinity regions come into contact with each other they create a semipermeable membrane as shown in the diagram below.
Low salinity regions mostly comprise of water due to low salt or ion concentration whereas, hydrocarbons in a reservoir have higher salt or ion concentrations. The region where water comes into contact with the hydrocarbons, a semipermeable membrane is formed. This membrane allows water molecules to get pulled up along with the hydrocarbon during the production process. This is why during enhanced oil recovery techniques, water or steam is injected into the well, so that it can push the hydrocarbons further because of osmotic pressure creation beneath and improve the production levels.