Contents
Material Wettability, Wicking and Microfluidics

Wettability Alteration Screening for Surfactants and Chemicals: Contact Angle and Interfacial Tension on One Bench

Rank surfactants and chemicals by how far they shift an oil wet surface toward water wet, and by how much they lower oil and water interfacial tension, before you commit core or field time.

Who this is for: Enhanced oil recovery, production chemistry and formulation labs that screen surfactants, nanofluids and brines.

Where it fits: Early screening on aged mineral plates and fluids, before imbibition, Amott or coreflood tests.

What it does not do: It does not give core scale wettability indices, and pendant drop cannot measure ultralow interfacial tension.

Method
Contact angle of oil on aged plates under brine, plus pendant drop surface and interfacial tension
Standard
No contact angle screening standard found; API RP 40 covers core analysis
Setup
About 2 minutes
Book a 15 minute demo Request a quote
Production of detergent, blue liquid boiling and fuming in flask, chemistry
Why it matters

Why wettability alteration is worth screening

50.7° to 104.0°

water contact angle on calcite after 22 days of aging in crude oil; SDS treatment then brought it down to 27.4°.

Ebrahimi et al., Scientific Reports 14, 2024

129° to 30°

contact angle on aged carbonate rock after soaking in a tuned brine, the best of the brines tested.

Ahmadi, Riazi, Malayeri, SCA2017-102, Society of Core Analysts, 2017

Up to several months

time that Amott and USBM wettability tests on cores can take, against hours to days for a contact angle screen on plates.

Repina et al., E3S Web of Conferences 367:01006, 2023

Sources: Ebrahimi et al., Toward mechanistic understanding of wettability alteration in carbonate rocks, Scientific Reports, 2024; Ahmadi, Riazi, Malayeri, Investigation of wettability alteration of carbonate rock in presence of sulfate, calcium and magnesium ions, SCA2017-102; Repina et al., E3S Web of Conferences, 2023. Figures come from these sources, not from Droplet Lab measurements.

Quick reference

What this wettability alteration screen does and what it does not

A quick reference for chemistry labs checking fit before reading further.

Evidence Box

Problem this solves

Too many surfactant and brine candidates for core tests, and no fast way to rank how each changes wetting and interfacial tension.

Standards

No standard prescribes a contact angle screen for wettability alteration. API RP 40 covers core analysis, including core handling to preserve wettability, not contact angle.

Peer reviewed method

The Dropometer drop shape method was validated against a KRUSS DSA100E in two peer reviewed papers, in Review of Scientific Instruments and Colloids and Surfaces A.

Customer case study

A University of Waterloo rheology lab measured surface and oil and water interfacial tension on a Droplet Lab tensiometer in seven publications, 2025 to 2026.

Customer publication

A Colloids and Interfaces (2025) study measured mineral oil and water interfacial tension falling from 57.2 to 3.02 mN/m with 1 wt% SDS, 10 readings per solution.

Honest limit

Pendant drop works down to about 1 mN/m. Ultralow interfacial tension for surfactant flooding needs a spinning drop tensiometer.

Who this is for

What wettability alteration question are you trying to answer?

Pick the card closest to your role. Each one points to the part of this page that answers it.

EOR or production chemist

You have a list of surfactants, nanofluids or brines. Contact angle on aged plates and interfacial tension rank them before you spend core and coreflood time.

Age every plate in the same oil, at the same temperature and time.

Formulation scientist

You tune surfactant blends for wetting on another surface, such as leaves, fabrics or minerals. The same contact angle and tension pair shows what each change does.

Measure surface tension and CMC before you test wetting.

University research group

Students compare chemicals across many brines and surfaces. One locked method keeps results comparable from one project to the next.

Report temperature, aging and equilibration time with every value.
Fit check

Is this the right screen for your chemicals?

It measures contact angle and surface or interfacial tension on bench samples. It does not test cores.

Good fit if

You rank many surfactants or brines before core tests.
You can prepare flat polished mineral plates.
Your interfacial tension is above about 1 mN/m.
You want surface tension, CMC and contact angle from one kit.
You measure at room temperature or close to it.

Less relevant if

You need ultralow interfacial tension; use a spinning drop.
You need reservoir pressure and temperature in a cell.
You need Amott or USBM indices on cores.
Your crude oil is too dark to image against brine without care.
Summary

How contact angle and interfacial tension rank wettability alteration chemicals

The answer in under a minute.

Age polished mineral plates in oil, then measure the contact angle of an oil drop under brine before and after soaking in each candidate solution. Measure surface tension, CMC and oil and water interfacial tension for the same solutions. Shortlist the chemicals that move the angle furthest toward water wet at the lowest dose, then confirm on cores.

The Dropometer contact angle and surface tension kit runs both measurements. The University of Waterloo case study shows a lab measuring oil and water interfacial tension with surfactants, and the cellulose nanocrystal and surfactant emulsion study reports the full method. The API RP 40 page covers core analysis, and our oil and gas guide and surface tension measurement guide explain more.

Expert Quote

Expert perspective on surfactant screening

“

The critical micelle concentration is not a number you look up; it is where the surface tension curve flattens, and the only honest way to know it is to measure it.

Dr. Alidad Amirfazli

Professor, Department of Mechanical Engineering, York University; Co-founder, Scientific Advisor, Droplet Lab

The problem

Why wettability alteration chemicals are hard to rank

Oil reservoirs and many industrial surfaces start water wet and turn oil wet as polar oil components adsorb. In one study, calcite went from 50.7° to 104.0° after 22 days in crude oil. Chemicals that shift the surface back toward water wet can release oil that waterflooding leaves behind, and the US Department of Energy puts secondary recovery at only 20 to 40% of the oil in place. The core tests that prove it, Amott and USBM, can take months, so labs cannot run them on every surfactant, nanofluid and brine. Contact angle on aged mineral plates ranks candidates in days, but results move with aging, temperature, roughness and equilibration time. In one study the same surfactant left calcite oil wet at 25 °C and made it water wet at 70 to 90 °C. Some surfactants even push a surface toward oil wet. Interfacial tension is the second lever, and pendant drop stops working below about 1 mN/m, where ultralow tension formulations sit.

Too many candidates for the core and coreflood budget.
Imbibition tests take weeks per chemical.
Contact angles on plates disagree between operators.
A chemical lowers interfacial tension but does not change wetting.
Results from different labs cannot be compared.
Troubleshooting

Why wettability screening results vary and what to check

Why:

  • Oil wet behaviour depends on oil composition, aging temperature and time.

How to detect:

  • Untreated aged plates do not read the same baseline angle.

Corrective action:

  • Age all plates in the same oil, temperature and time, and measure an untreated plate in every batch.

Why:

  • Roughness and residue change the apparent angle before any chemical acts.

How to detect:

  • Spread between spots on one plate is large.

Corrective action:

  • Polish and clean plates the same way and record the procedure.

Why:

  • Chemicals adsorb and the angle keeps changing for hours or days.

How to detect:

  • The angle still moves between repeat readings.

Corrective action:

  • Fix the soaking and equilibration time and read at the same time for every candidate.

Why:

Dose relative to CMC changes adsorption. Our CMC experiment shows how to find it.

How to detect:

  • Two doses of the same chemical rank differently.

Corrective action:

Measure CMC first, then test at set multiples of it. Our CMC reference values help as a check.

Why:

  • Below about 1 mN/m the drop detaches or deforms and the fit fails.

How to detect:

  • Drops fall off the needle or give unstable fits.

Corrective action:

  • Report as below the pendant drop range and confirm on a spinning drop tensiometer.

Why:

Drop volume, temperature and timing change results. Our guide to reproducible contact angle measurement covers fair comparisons.

How to detect:

  • A reference chemical reads differently between sessions.

Corrective action:

  • Run a reference chemical in every session and lock the method.

Not sure your screening results are comparable?

Send your plate preparation and two candidate chemicals, and we will review the method on a call.

Book a 15 minute demo
Lab records

What a wettability screening record contains

Each run produces a record you can file with the chemical and compare across projects.

Substrate

Mineral, polishing, cleaning and aging oil, time and temperature.

Fluids

Brine composition, chemical, dose and its CMC.

Method settings

Drop volume, geometry, soaking and equilibration time, temperature.

Readings

Angle before and after, surface and interfacial tension, with n and spread.

Confirming test

Imbibition, Amott or coreflood result for shortlisted chemicals.

Drop images

Automatic edge and baseline detection gives the same reading from the same image, so a reviewer can recheck any result.

Measurements

What to measure when screening wettability alteration

Wetting

Contact angle on aged plates, before and after treatment

Why it matters: It shows how far each chemical moves the surface toward water wet.

How to interpret: Commonly used ranges: water wet up to about 60 to 75°, intermediate to about 105 to 120°, oil wet above that. Labs draw the lines differently, so report yours.

When it is not enough: A polished plate does not show rock heterogeneity or pore effects.

Hysteresis

Advancing and receding angles

Why it matters: A single static angle can mislead on rough or mixed surfaces.

How to interpret: On one dolomite, advancing angles near 152° came with receding angles of 23 to 26°.

When it is not enough: It still reads one spot on one plate.

Interface

Oil and water interfacial tension by pendant drop

Why it matters: Lower tension helps release trapped oil.

How to interpret: Compare candidates at the same dose; with SDS, mineral oil and water fell from 57.2 to 3.02 mN/m in one Dropometer study.

When it is not enough: Below about 1 mN/m the drop detaches; use a spinning drop.

Dose

Surface tension and CMC in your brine

Why it matters: Adsorption and wetting change depend on dose relative to CMC.

How to interpret: Find the break in the surface tension curve, then test at set multiples of it.

When it is not enough: Brine salinity and temperature shift CMC; measure in your own brine.

Validation

Validated measurement approach for surfactant screening

How the Dropometer itself has been validated, and how a customer measured surfactant interfaces with it.

Peer reviewed method

The Dropometer drop shape method is published in Review of Scientific Instruments and Colloids and Surfaces A. Contact angle was validated against a KRUSS DSA100E, with a published accuracy of 0.35°.

See the validation papers

Customer evidence on surfactant interfaces

University of Waterloo researchers measured surface and mineral oil and water interfacial tension with a Droplet Lab tensiometer, 10 readings per solution at 22 ± 1 °C. SDS lowered interfacial tension from 57.2 to 3.02 mN/m at 1 wt%, while cellulose nanocrystals alone reached only 38.3 mN/m (Colloids and Interfaces, 2025).

Read the citation analysis
QC Protocol

How to screen wettability alteration chemicals

Six steps per candidate. Keep every step identical between chemicals.

1

Characterise fluids

Measure surface tension and CMC of each chemical in your brine. Our surface tension guide explains the pendant drop method.

2

Prepare plates

Polish and clean mineral plates the same way, then age them in oil at a fixed temperature and time.

3

Baseline

Measure the oil drop contact angle under brine on an untreated aged plate.

4

Treat

Soak aged plates in each candidate solution for the locked time.

5

Measure

Measure the angle again and the oil and water interfacial tension for the same solution. Our capillary number entry explains why both matter.

We completed our gage R&R study on the unit and it performed very well.

Brandon Barbee

Corporate Quality Engineer, Zeus Industries, Polymer Manufacturing

Download the wettability alteration screening SOP

A two page SOP you can adapt for your chemicals, with plate aging, the method lock, ranking rules, a troubleshooting table and a record sheet.

Contact angle measurement with the Dropometer

Example output

Example wettability alteration screening log

Example data only. Your values will differ with mineral, oil, brine and aging.

How to read this log

The untreated aged plate sets the baseline. Chemical A moved the plate furthest toward water wet. Chemical B lowered interfacial tension most but moved the angle less. Chemical C did little at this dose. The last row fell below the pendant drop range, so it needs a spinning drop check. Our page on drilling and fracturing fluid surfactant screening covers related fluids.

Example wettability alteration screening log

Sample Dose Angle after treatment (°) Shift from baseline (°) Interfacial tension (mN/m) Decision
Untreated aged plate None 145 0 28 Baseline
Chemical A 2 x CMC 70 75 6 Shortlist
Chemical B 2 x CMC 105 40 2 Shortlist, check wetting
Chemical C 2 x CMC 138 7 15 Reject
Chemical D 2 x CMC 95 50 Below range Confirm on spinning drop

Example data, not customer data. Angle measured through the water phase on aged calcite plates; interfacial tension by pendant drop at room temperature; n = 3.

Signal order

The order to check signals when ranking chemicals

Check these in order. Each one rules out a cause before you look at the next.

1

Fluid surface tension and CMC

Confirms each chemical is dosed as intended.

2

Untreated baseline

Confirms plates aged the same way.

3

Angle shift

Shows how far each chemical moves wetting.

4

Interfacial tension

Shows the second lever, and whether it is in pendant drop range.

5

Core test

Confirms what the screen predicts. Our page on leaf coverage uses the same surfactant logic on plants.

FAQ

Common questions about wettability alteration screening

Questions chemistry labs ask about contact angle and interfacial tension screens.

What contact angle means water wet or oil wet?

Commonly used ranges after Anderson put water wet up to about 60 to 75°, intermediate up to about 105 to 120°, and oil wet above that, measured through the water phase. Other labs use 75 and 105°, or 80 and 100°. State the cut offs you use with every result.

How long should plates age in oil?

Long enough for the baseline to stop moving. Published work aged calcite for 5 to 22 days and cites 2 to 4 weeks for stable wetting. Age every plate in the same oil, at the same temperature and time, and measure an untreated aged plate in each batch.

Can the Dropometer measure ultralow interfacial tension?

No. Pendant drop needs a drop that hangs with a clear neck, and below about 1 mN/m the drop detaches from the needle. Surfactant flooding often targets 10-3 mN/m, which needs a spinning drop tensiometer. Use pendant drop to rank chemicals in the mN/m range.

Why measure at room temperature if the reservoir is hot?

Because a bench screen ranks candidates; it does not predict the reservoir. In one study a surfactant left calcite oil wet at 25 °C and water wet at 70 to 90 °C, so test shortlisted chemicals at reservoir temperature on cores or in a heated cell before you decide.

Which surfactants work best on carbonates?

Cationic surfactants such as CTAB are often reported as the most effective on calcite, compared with anionic and nonionic ones. Results depend on mineral content, oil and temperature, and some anionic surfactants have pushed dolomite toward oil wet. Screen your own candidates on your own plates.

How is this different from Amott or USBM tests?

Amott and USBM measure the average wettability of a whole core, and can take months. A contact angle reads one polished plate in hours to days. Use the plate screen to shortlist, then run core tests on the few chemicals that matter.

Does API RP 40 cover this?

Not directly. API RP 40 gives recommended practices for core analysis, including handling cores to preserve wettability. It does not prescribe a contact angle screen, so report your full method alongside the results.

Business impact

What changes when you screen before core tests

Typical changes in how labs work. Benchmarks are given only where a published source exists.

Before and with a bench screen

Metric Before Dropometer With Dropometer Indicative Benchmark
Time to a first ranking Core tests for each candidate Plate contact angle in hours to days Amott and USBM up to several months (Repina et al., 2023)
Candidates tested A few per year Many per project, shortlist to cores No published benchmark; track on your own projects
Wetting change measured Inferred from recovery Angle before and after treatment Calcite 104.0° aged to 27.4° with SDS (Ebrahimi et al., 2024)
Interfacial tension Sent out or estimated Pendant drop in the same session 57.2 to 3.02 mN/m with SDS (Kim and Pal, 2025, Dropometer)

See the measurement on your own fluids

Send two candidate chemicals and your brine. We will show the readings on a call.

Book a 15 minute demo

Estimate saved core tests from a bench screen

Enter your own numbers. The result is an estimate, not a Droplet Lab claim.

Screening estimate

Estimate saved core tests from a bench screen.

Each Dropometer unit is US$5,000; the default models one unit.
Your own cost to run imbibition, Amott or coreflood tests on one candidate.
Plate aging, contact angle and interfacial tension measurement per candidate.
No published benchmark. Use your own estimate and start low if unsure.

Result

~0
Candidates saved per month
~0
Monthly savings
~0
Payback period
~0
First year net benefit

Monthly savings = materials saved + technician time saved from reduced iterations.

Limits

What a bench screen cannot tell you

Honest limits, so you know when to reach for another test.

Polished plates are not rock pores.
Pendant drop stops working near 1 mN/m.
Bench temperature is not reservoir temperature.
Results depend on aging oil, time and temperature.
It does not give Amott or USBM indices.
Equilibrium can take hours or days.

Contact angle and interfacial tension on bench samples rank chemicals. Core scale wettability, recovery and behaviour at reservoir conditions need core tests.

Book a 15 minute demo Request a quote
Related

Standards, evidence and related surfactant workflows

These pages cover core analysis, customer evidence and the surfactant checks that sit beside this one.

Standard

API RP 40

Recommended practices for core analysis.

View standard

Case study

University of Waterloo

Surface and interfacial tension in seven publications.

Read case study

Published paper

Cellulose nanocrystals and surfactants in emulsions

Oil and water interfacial tension with four surfactants.

Read our analysis

Instrument

Dropometer

Contact angle, surface tension and interfacial tension.

View product

Related use case

Material wettability, wicking and microfluidics

All wettability and wicking use cases in one place.

View Page

Related use case

Drilling and fracturing fluid surfactant screening

Surface tension checks on oilfield fluids.

View Page

Related use case

Leaf coverage and spray wetting

Surfactants that change wetting on leaves.

View Page

Guide

Dynamic surface tension

Why surface age matters for surfactants.

Read guide

How this page was created

Editorial and technical transparency notes for this page.

Transparency Details 4 checklist items
01

Drafting assistance

Drafted with Claude Opus 5.5 (Anthropic) using web search for sources, then edited by the Droplet Lab team.

02

Technical review

Reviewed and edited for technical accuracy by the Droplet Lab Team.

03

Verification steps

Standard identifiers, units, thresholds and key procedural claims are checked against cited sources before publication.

04

Updates

Reviewed every 12 months or when the underlying method changes.

Report a correction

Spotted an issue in this summary? Send a correction request and our team will review it.

Correction Request

We work hard to keep this page accurate and up to date. If you spot an error (wrong revision/year, missing requirement, incorrect interpretation, or broken link), tell us and we'll review it.

Contact us to report a correction
Sources

References

1.
Anderson, W. G. Wettability literature survey, part 2: wettability measurement. Journal of Petroleum Technology 38:1246 to 1262, 1986. Ranges as tabulated in the AAPG Wiki entry on wettability. https://wiki.aapg.org/Wettability
2.
Ebrahimi et al. Toward mechanistic understanding of wettability alteration in carbonate rocks in the presence of nanoparticles, gelatin biopolymer, and core shell nanocomposite of Fe3O4@gelatin. Scientific Reports 14, 2024. https://www.nature.com/articles/s41598-024-80893-2
3.
Ahmadi, Riazi, Malayeri. Investigation of wettability alteration of carbonate rock in presence of sulfate, calcium and magnesium ions. SCA2017-102, Society of Core Analysts, 2017. https://jgmaas.com/SCA/2017/SCA2017-102.pdf
4.
Jarrahian, Vafaie-Sefti, Ayatollahi, Moghadam, Mousavi Moghadam. Study of wettability alteration mechanisms by surfactants. SCA2010-38, Society of Core Analysts, 2010. https://jgmaas.com/SCA/2010/SCA2010-38.pdf
5.
Mohanty, K. K. ACS Petroleum Research Fund report 46419-AC9, 2009. https://acswebcontent.acs.org/prfar/2009/reports/P10188.html
6.
Xu, Ayirala, Rao. SCA2005-53, Society of Core Analysts, 2005. https://jgmaas.com/SCA/2005/SCA2005-53.pdf
7.
Al-Attar, Abubacker, Zekri, Khalifi, Lwisa. Contact angle and IFT measurements at elevated temperatures for evaluating wettability in a selected carbonate reservoir in the UAE. SCA2016-076, 2016. https://jgmaas.com/SCA/2016/SCA2016-076.pdf
8.
AlZaabi et al. Impact of carbonate mineral heterogeneity on wettability alteration potential of surfactants. Fuel 342:127819, 2023. https://ro.ecu.edu.au/ecuworks2022-2026/2079
9.
Repina et al. E3S Web of Conferences 367:01006, 2023. https://www.e3s-conferences.org/articles/e3sconf/pdf/2023/04/e3sconf_sca2022_01006.pdf
10.
Han, Lu, Fan, Li, Holmberg. Tenside Surfactants Detergents 58(3):164 to 176, 2021. https://research.chalmers.se/publication/524188/file/524188_Fulltext.pdf
11.
Huhtamaki et al. Surface wetting characterization using contact angle measurements. Nature Protocols 13:1521 to 1538, 2018. https://dx.doi.org/10.1038/s41596-018-0003-z
12.
SLB Energy Glossary. Spinning drop tensiometer. https://glossary.slb.com/terms/s/spinning-drop_tensiometer
13.
US Department of Energy. Enhanced oil recovery. https://www.energy.gov/hgeo/enhanced-oil-recovery
14.
Kim, Pal. Influence of cellulose nanocrystals and surfactants on catastrophic phase inversion and stability of emulsions. Colloids and Interfaces 9:46, 2025. See our citation analysis. https://dropletlab.com/validation/citations/analysis/influence-of-cellulose-nanocrystals-and-surfactants-on-catastrophic-phase-inversion-and-stability-of-emulsions/
15.
University of Waterloo case study: surface tension next to every flow curve. See the case study. https://dropletlab.com/validation/case-studies/waterloo-rheology-surface-tension-pendant-drop/
16.
Marquez, R., Bullon, J., Forgiarini, A., Salager, J. L. The oscillatory spinning drop technique: an innovative method to measure dilational interfacial rheological properties of brine crude oil systems in the presence of asphaltenes. Colloids and Interfaces 5(3):42, 2021. https://www.mdpi.com/2504-5377/5/3/42
17.
API Recommended Practice 40. Recommended practices for core analysis, second edition, 1998. https://energistics.org/sites/default/files/2022-10/rp40.pdf
18.
Chen, X. et al. Contact angle measurement with a smartphone. Review of Scientific Instruments 89(3):035117, 2018. https://pubs.aip.org/aip/rsi/article-abstract/89/3/035117/368179/Contact-angle-measurement-with-a-smartphone
19.
Surface tension measurement with a smartphone using a pendant drop. Colloids and Surfaces A: Physicochemical and Engineering Aspects. https://www.sciencedirect.com/science/article/abs/pii/S0927775717307744
20.
Droplet Lab validation papers
21.
Customer publications that cite the Dropometer
22.
Surface tension measurement guide
23.
Oil and gas guide