Enhanced oil recovery
Enhanced oil recovery (EOR) is a set of techniques used to increase the quantity of hydrocarbons extracted from a deposit.
The four enhanced oil recovery techniques
There are essentially four different techniques for improving oil recovery and extracting 30 to 60% of the stock, instead of the 20 to 40% recoverable using conventional methods.
- First of all it is possible to inject gas (natural gas, nitrogen, CO2) into the well to increase the pressure and, sometimes, reduce the viscosity of the hydrocarbons. The injected gas remains trapped in the well. This technique can therefore be used to combine increased crude oil recovery with geological storage of CO2.
- Chemical diluent or surfactant solutions can also be used to reduce surface tension and capillary pressure in oil wells.
- The injection of certain micro-organisms is a way to reduce the length of carbon chains while generating in situ surfactants and CO2 which reduce the viscosity of crude oil.
- Finally, the injection of water vapour helps reduce the viscosity and vaporise a fraction of the crude oil.
Without these techniques, it would not be possible to extract hundreds of thousands of cubic metres of crude oil from geological reservoirs.
Output at the Lost Hills Oil Field continues to increase, contrary to the output of other Californian oil fields, thanks to EOR. © Richard Masoner CC by-sa 2.0