Pour point
- Also known as
- pour point depressant
The pour point is the lowest temperature at which an oil will still flow under standard test conditions. Below it, wax crystals or high viscosity make the oil behave almost like a solid. For crude oil it is measured by methods such as ASTM D97 and ASTM D5853.
What is the pour point?
As a waxy oil cools, dissolved paraffin waxes begin to crystallize. With further cooling, the crystals grow and link into a network that traps the liquid oil, until the oil stops flowing. The pour point is the temperature near which that happens. It is determined by cooling a sample under specified conditions and checking at regular temperature intervals whether it still moves when the container is tilted.
ASTM D97 covers petroleum products generally, and ASTM D5853 is a method specifically for crude oils.
Pour point and wax appearance temperature
Wax begins to crystallize at the wax appearance temperature, which is higher than the pour point. Between the two temperatures, the oil still flows but carries wax crystals and can deposit wax on cold surfaces, causing paraffin deposition. Below the pour point, the oil can gel.
Why it matters
- Pipeline restarts. If a pipeline carrying high-pour-point crude shuts down and cools, the oil can gel and require high pressure to restart.
- Storage and transport in cold climates and subsea environments.
- Production. Wells that are shut in can face gelled oil on restart.
These issues are part of flow assurance.
Managing high pour points
- Pour point depressants, polymers that interfere with wax crystal growth so that crystals stay small and do not form a network.
- Heating and insulation of lines and tanks.
- Dilution with lighter oils or solvents.
Frequently asked questions
For handling in cold conditions, yes: a lower pour point means the oil stays fluid at lower temperatures.
Not necessarily. It mainly improves flow of the bulk oil. Deposition on cold surfaces may need other treatments, such as paraffin inhibitors or dispersants.
Sources
- ASTM D97 Standard Test Method for Pour Point of Petroleum Products, ASTM International
- ASTM D5853 Standard Test Method for Pour Point of Crude Oils, ASTM International
- pour point, SLB Energy Glossary