Demulsifiers: Breaking Oil/Water Emulsions (Basics)

Executive summary (what demulsifiers actually do)

Oil/water emulsions form when water droplets are dispersed in crude oil (or oil droplets dispersed in water) and stabilized by interfacial films (asphaltenes, resins, fine solids, surfactants, corrosion inhibitors, etc.). A demulsifier is typically a surfactant blend designed to:

• Displace or weaken the interfacial film around droplets.
• Promote coalescence (small droplets merge into larger ones that settle faster).
• Improve water drop and reduce the “rag layer” (emulsion pad) in separators and treaters.
• Protect downstream (heater treater, electrostatic treater, desalter) by reducing carryover and salts/BS&W.

Where it fits (production & processing)

Demulsifiers are used across the separation chain. Your injection point depends on residence time and mixing energy:

• Wellhead / flowline: early “conditioning” with long residence time; helps reduce stable emulsions before first separator.
• 1st/2nd stage separator: common point when you have sufficient mixing and predictable residence time.
• Heater treater / FWKO: supports water drop and rag layer reduction, especially in heavy crude and high BS&W.
• Electrostatic treater / desalter: focuses on reducing salt and residual water before export/refining interface.

Emulsion types (know what you’re breaking)

• W/O (water-in-oil): most common in crude production; target is faster water drop and cleaner oil.
• O/W (oil-in-water): common in produced water handling; requires different chemistry (often clarifiers/coagulants rather than classic crude demulsifiers).
• Multiple emulsions: W/O/W or complex rag layers; often driven by fine solids and mixed chemical programs.

What makes an emulsion “hard” to break

These are the usual drivers of stubborn emulsions and persistent rag layers:

• Asphaltenes/resins: strong interfacial films, especially in heavier crudes.
• Fine solids: clays, corrosion products, scale fines; solids-stabilized emulsions often need multi-step treatment.
• High viscosity (cold, heavy oil): slows droplet movement and coalescence.
• High shear mixing: chokes, pumps, valves create small droplets that settle slowly.
• Incompatible chemical programs: some corrosion inhibitors, wax inhibitors, and scale inhibitors can stabilize emulsions.
• Salinity and pH shifts: can change surfactant behavior and droplet charge.

Demulsifier chemistry families (high-level)

Supplier formulations vary, but demulsifiers are commonly built on nonionic surfactant backbones and resins. Typical families include:

• EO/PO block copolymers: tunable hydrophilic-lipophilic balance (HLB) for W/O breaking and coalescence.
• Resin-based demulsifiers: strong film-displacement characteristics for asphaltenic crudes.
• Ethoxylated phenolic resins / surfactant blends: often used for difficult emulsions with persistent rag layers.
• Solvent carriers: aromatic/aliphatic/oxygenated solvents used to deliver actives and control viscosity/pour point.

For procurement: chemistry family matters because it affects flash point, VOC profile, and elastomer compatibility (plus transport classification).

Selection matrix (crude + equipment → what to optimize)

• Light crude, low solids: optimize fast water drop and low residual water (BS&W) at low ppm.
• Heavy crude, high viscosity: optimize film break + coalescence; heat + mixing energy become more important.
• High solids / dirty systems: optimize rag layer reduction; may require solids handling and compatible upstream chemicals.
• Electrostatic treater/desalter: optimize conductivity and droplet coalescence behavior; avoid products that create stable rag layers under electric fields.
• Produced water O/W issues: evaluate separate water clarifier program (don’t force a crude demulsifier to do a water clarifier’s job).

Typical dosage ranges (starting points)

Real dosage is site-specific. Use these as screening ranges for trials:

Always specify dose as ppm on total fluid or on crude phase (be consistent). Ask suppliers for “active content” guidance so you can compare apples-to-apples.

Bottle test workflow (simple, repeatable, procurement-friendly)

Bottle tests are quick screens to shortlist candidates before field trials. The goal is to compare products at fixed conditions. A basic workflow:

1. Collect representative sample: take from a point that reflects actual emulsion (avoid stratified sampling). Record temperature and time since sampling.
2. Control temperature: test at field-relevant temperature (or at multiple temperatures if you operate across seasons).
3. Dose series: e.g., 5 / 10 / 25 / 50 / 100 ppm to see the response curve (watch for overdose behavior).
4. Mixing: consistent inversion count or shaker time (don’t change shear between candidates).
5. Readouts at fixed times: water drop (mL), interface sharpness, rag layer thickness, clarity of separated water, oil haze.
6. Scorecard: pick the top 2–3 for a controlled field trial.

What “good” looks like

• Fast water drop without creating a thick rag layer.
• Sharp interface (easy to control level in separators).
• Clear separated water (lower oil carryunder) and clean oil (lower BS&W).
• Dosage robustness: performance doesn’t collapse if operations drift slightly.

Field trial guidance (minimize risk)

• Pick a stable window: avoid running trials during major throughput changes or maintenance upsets.
• One change at a time: keep heater temperature, level control, and mixing devices constant.
• Track the right KPIs: BS&W, export water cut, salt (if relevant), rag layer volume, slop/oily water loads, chemical consumption.
• Watch interactions: corrosion inhibitor changes can affect emulsion stability; coordinate with the chemical program owner.

Specification & acceptance checks (COA/SDS + incoming QC)

For demulsifiers (usually liquid concentrates), request and verify:

• Identity: product name/grade, manufacturer, batch/lot, production date, shelf life.
• COA typical items: active content (if disclosed), density, viscosity, appearance, water content (if relevant), pH (if water-based), flash point (if solvent-based), pour point.
• Carrier solvent details: hydrocarbon vs oxygenated solvent; implications for VOC, odor, and transport classification.
• Safety: current SDS, PPE, spill response, compatibility notes (gaskets/hoses), firefighting guidance.
• Packaging: drums/IBCs/bulk, liner/valve type, labels with lot number, tamper seals.
• Logistics: Incoterms, lead time, temperature limits (freeze/heat), storage conditions, return policy for IBCs.

Incoming QC: quick checks you can implement

• Visual: stratification, sediment, haze, crystallization.
• Density/viscosity fingerprint: simple checks vs COA help detect dilution or drift.
• Small bottle test recheck: use a retained reference emulsion sample where possible for trend monitoring.

Troubleshooting signals (symptom → likely causes → first checks)

Handling & storage (EHS + operations)

• Storage: keep sealed; protect from water ingress and temperature extremes; use bunding/secondary containment.
• Materials compatibility: verify pump seals, hoses, and gasket compatibility with the solvent system.
• Fire safety (solvent-based): observe flash point guidance and site ignition control practices.
• Traceability: record lot numbers and consumption by day for claims management and performance audits.

RFQ notes (send this for accurate selection + pricing)

• Crude API gravity, viscosity range, BS&W %, and typical temperature at injection point.
• Solids content notes (sand/fines), asphaltene/resin tendency (if known), and crude blend variability.
• Separation equipment: separator stages, heater treater/FWKO, electrostatic treater/desalter, residence times.
• Water phase: salinity, pH, treatment constraints, produced water discharge requirements (if relevant).
• Current chemical program (demulsifier/corrosion inhibitor/scale inhibitor/wax inhibitor) at a high level.
• Volume, packaging preference (drum/IBC/bulk), delivery location, Incoterms, documentation needs (SDS/COA, change control).

Educational content only. Always follow site EHS rules and the supplier SDS for safe use. Field performance depends on crude blending, temperature, shear history, and separator operation—validate with your site trial plan.