Injection water

Oil producers often inject water into subterranean reservoirs to keep the pressure up and extract as much oil as possible. The injection water has to meet high standards to optimize oil recovery.




  • Horizontal dead-end ultrafiltration pretreats seawater
  • Horizontal dead-end ultrafiltration delivers the best feedwater quality to sulfate removal package plants 
  • Robust Crossflow process treats produced water for re-injection or safe disposal
  • Small footprint
  • Low energy consumption

application areas

During the early life of an oil field, production is relatively easy. Reservoir pressure will gradually drop and make it increasingly harder to bring the oil to the surface. When production goes below acceptable levels, oil companies often have to inject water into the reservoir to increase pressure and force the oil out. Some oil reservoirs benefit from injecting low-salinity water, chemicals, or a combination. 

The three main sources for water injection are seawater (offshore), river/lake/well water (onshore) and produced water (on- and offshore). 

Seawater may need to have sulphate removed, as it could cause souring and precipitation of barium and strontium in the reservoir. Sulfate removal membranes need good pretreatment. 

Produced water is the injection water that comes back up again with the oil. Increasingly strict environmental regulations are limiting or even prohibiting its disposal. Re-injecting produced water has therefore become an attractive alternative to seawater or surface water injection. 

pentair solutions

Ultrafiltration (UF) is known for the complete removal of all suspended solids and free/disperged oil. With a permeate quality of <1 mg/ltr TSS and <1 mg/ltr oil, UF is most suitable to deliver high-quality feedwater to downstream reverse osmosis (RO), nanofiltration (NF) and ion exchange (IX) systems, or to sulphate removal processes (SRP), (chemically) enhanced oil recovery (CEOR) and steam-assisted gravity drainage (SAGD). Pentair’s robust UF membrane systems are operated in dead-end or crossflow configuration. 

The dead-end operation mode, with a small footprint and low energy consumption, is very suitable for (sea)water applications in which the feed has an oil content of less than 5 mg/ltr, and TSS of less than 30-50 mg/ltr.

Crossflow operation concentrates the oil fraction 10 to 20 times and needs little chemical cleaning compared to conventional systems. It is better suited for much higher TSS concentrations (<200 mg/ltr), combined with an oil content of less than 1000 mg/ltr. 

If you have any questions, please contact us.

Featured cases

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Heilongjiang province, China

Produced water

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