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PhD Defense by Muhammad Adeel Nasser Sohals

Muhammad Adeel Nasser Sohals, Department of Chemistry and Bioscience, will defend his thesis on "Enhanced Oil Recovery Based on Ionically Modified Water in Carbonates".


13.01.2017 kl. 13.00 - 16.00



"Enhanced Oil Recovery Based on Ionically Modified Water in Carbonates"


The wettability alteration process depends on the formation water composition, crude oil chemistry, reservoir temperature, rock surface mineralogy and composition of the injected water. The study of all the parameters is important to understand their role in wettability alteration mechanisms, but injected water chemistry is the only that can be tuned at reservoir scale. Therefore, this study principally focused on the investigation of water chemistry effects on wettability including: a) effect of potential scale forming ions on initial wetting conditions, b) effect of ionic composition and strength, c) influence of temperature, d) impact of oxyanions concentration, and e) interfacial tension.

This study used flotation to measure wettability. Comparisons of wettability trends measured by flotation with imbibition showed flotation produced similar results. The experiments used Dan chalk, reservoir oil and synthetic brines were performed at 23, 50 and 100oC. The flotation technique directly measures the wettability and physically separates oil-wet rock from water-wet rock. The resulting measurement is expressed as % water-wet grains. A flotation wettability index (FWI) was defined and works in the same way as Amott wettability index by expressing the wetting condition with a numerical value between completely oil-wet (-1) and water-wet (+1). The technique also allows determination of the amount of oil retained on water-wet surfaces after wettability alteration. The retained oil offers additional information on the wettability alteration mechanisms compared to other wettability measurement techniques.

The experimental results show that changing water chemistry can improve the oil wetness or water wetness. The first effect, improving oil wetting, was found to be associated with an ionic composition, specifically addition of oxyanions, while reducing the ionic strength (dilution) improved the water-wet conditions of the crude-oil-brine (CBR) system. The addition of the oxyanions sulfate and borate shifted the wettability to more oil wet. All the brines had Ca and Mg present so we could not isolate any specific effects associated with the cations. Sulfate was temperature sensitive with little shift at 23 and 50oC as concentration increased, but at 100oC the wettability shift was pronounced from neutral to oil wet. Borate showed less temperature sensitivity and less ability to shift wettability. The wettability shift for both oxyanions was proportional to concentration. Dilution of the brines increased the water-wet conditions up to 10-fold dilution, but further dilutions did not increase water wetting. Dilution changed wettability for formation brines from -0.50 to -0.75 (oil-wet) to -0.25 & 0.0. Increase in temperature shifted the CBR system towards more oil-wet for all the brines tested including the brines without sulfate or borate. The wettability shifted from near neutral-wet to more oil-wet conditions when the temperature increased from 23oC to 100oC. The temperature effect was different depending on oxyanion. Sulfate showed no temperature effect between 23 and 50oC, but showed significant shifting at 100oC with greater shift to oil wet with increasing sulfate concentration. In contrast, borate showed a systematic increase in oil wetting as temperature increased.

The interfacial tension (IFT) between crude oil and advanced fluids was measured at 23 and 90oC. IFT increased for seawater and seawater without sulfate as temperature increased from 23oC to 100oC, but decreased for seawater with borate. The dilutions of all the brines increased the IFT at constant temperature. The lowest IFT was 11.5 mN/m, which is not low enough to improve oil recovery independently without wettability alteration.


  • Professor MSO, Erik Gydesen Søgaard, Department of Chemistry and Bioscience, Aalborg University


  • Associate Professor, Saqib Sohail Toor (Chairman), Department of Energy Technology, AAU, Denmark 
  • Ph.D. and Senior Scientist, Patrick V. Brady, Geoscience Research & Applications Group, Mexico
  • Ph.D. and Project Manager, Vural Sander Suicmez, Maersk Oil and Gas A/S, Copenhagen K, Denmark





Department of Chemistry and Bioscience, Section of Chemical Engineering


Niels Bohrs Vej 8, 6700 Esbjerg

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