Upstream · Production
Produced water
On a mature field every barrel of oil comes with several barrels of water. That salty, hot water, laden with residual oil, is the site’s largest stream by volume and Exploration & Production’s first environmental subject. Treating it costs; reinjecting it holds pressure; valorising it is our Water-to-Value™ programme.
Where the water comes from, and why it grows
The water was there before the oil: formation water fills the rock under and around the oil. As you produce, it rises — the water cut, which grows with the field’s age. On Doba basin fields, produced for twenty years, the water cut often exceeds three quarters: “production” is first a production of water, from which oil is separated.
The treatment chain
- Primary separation — at the CPF, free water settles in the separators.
- De-oiling — hydrocyclones, flotation, filters: residual oil falls to a few tens of milligrams per litre.
- Filtration and conditioning — remove solids, inhibit corrosion and bacteria before injection.
- Reinjection — into the reservoir, to hold pressure and support production; or into a dedicated deep aquifer.
- Monitoring — water quality, injector well integrity, declared volume balance.
Water-to-Value™: water as a resource
Treated water is a resource. Reinjected, it is the carrier of secondary recovery and EOR — alkalis, surfactants and polymers dissolve in that water. Treated further, it can, depending on salinity and regulation, serve non-food crop irrigation, roads, concrete making, or controlled recharge. Every cubic metre that finds a use stops being a cost.
What we put in place
Skid-mounted de-oiling units, sized to the field’s water cut, movable.
Pressure maintenance as the default use; no untreated surface discharge.
Inhibitors and biocides formulated with our chemicals pole; natron as alkali in EOR loops.
Volumes produced, reinjected, valorised: declared and published, like payments.
Benchmarks
| Parameter | Order of magnitude | Stake |
|---|---|---|
| Water cut, mature field | 70 to 95% | volume to treat |
| Residual oil before injection | ≤ 30 mg/l | plugging, regulation |
| Salinity | varies by reservoir | possible uses |
| Treatment cost | a notable share of opex | field economics |
Onshore industry orders of magnitude; Doba values are field-specific.