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Oil-in-Water Chemistry: Free, Dispersed & Dissolved

Oil exists in produced water as free, dispersed and dissolved fractions, each governed by different physics and removed by different processes. Quantifying the droplet-size distribution is the starting point for any deoiling design.

How Oil Partitions in Produced Water

Free, Dispersed & Dissolved

Free oil (>150 micron) rises readily; dispersed oil (2–150 micron) needs enhanced separation; dissolved hydrocarbons require adsorption or biological polishing.

Droplet-Size Distribution

Pumps, chokes and valves shear oil into ever-finer droplets. The d50 of the distribution, not the total concentration, dictates which technology can remove it.

Stokes Rise Velocity

Rise velocity scales with the square of droplet diameter and the density difference, so coalescing larger droplets before separation is the most effective lever.

Emulsions and Shear

Emulsion Stabilisation

Natural surfactants, asphaltenes and production chemicals stabilise oil-water emulsions that resist gravity separation.

Shear History

Every pressure drop downstream of the wellhead reduces droplet size; minimising shear preserves separability.

Solids Interaction

Fine solids partition to the oil-water interface, stabilising emulsions and complicating both deoiling and solids handling.

From Chemistry to Process

Coalescence First

Plate packs and coalescing media enlarge droplets so that gravity and flotation can capture them.

Flotation for Fines

Induced or dissolved gas flotation lifts the dispersed fraction the separators leave behind.

Polishing for Dissolved

Adsorption media and biological steps address the dissolved hydrocarbons beyond physical separation.

Need a produced water treatment, reuse or reinjection solution?

Reynolds & Bauhm delivers this scope as part of an integrated, single-point engagement matched to your project, programme and regulatory regime.

Industries We Serve

Our expertise spans multiple industries with sector-specific water treatment solutions.