Study of Brine-Oil-Rock Interactions and wettability by help of adsorption enthalpies

Study of Brine-Oil-Rock Interactions and wettability by help of adsorption enthalpies
Jacquelin E. Cobosa Peter. Westhb and Erik G. Søgaarda
aDepartment of Chemistry and Bioscience, Aalborg University, Esbjerg, Denmark
bDepartment of Science and Environment, Roskilde University, Roskilde, Denmark
contact: egs@bio.aau.dk

The study we have performed is an attempt to determine the adhesion of different fluids onto the
rock surface of chalks at 75 o to mimic the processes that take place in an oil reservoir, in which the formation water during many years was in direct contact with the mineral surface before
oil invasion.
Two artificially produced formation waters corresponding to recipes of Valhal brine and Ekofisk brine were titrated into chalk and then crude oil was brought separately to those chalk-brine systems.
Everything was measured by help of Isothermal Titration Calorimetry (ITC) to be able to measure reaction adsorption enthalpies as an indirect measure of the wettability tendency of the liquids to 1) the chalk and 2) the chalk/brine systems. Finally, smart water as ionically modified seawater was added to the chalk/brine/oil systems. The results could give information of wettability alterations in the carbonate systems when using ionically modified seawater for water flooding.
The results from the experiments showed that the wettability of the chalk depends on the ionic composition of the formation water. In our case, Ekofisk brine made the rock more oil wet than Valhall brine which could be seen in the thermograms for the interaction between
the oil and the chalk-brine systems. In addition, thermograms showed the
substitution reactions of the calcium (Ca2+)by magnesium (Mg2+ ),which was enhanced by the presence of sulfate (SO42-). The research is still on-going and more interesting results on its way from this new methodology for oil reservoir wettability research.