The carbonate reservoirs are generally known as oil-wet; however, our experience in the laboratory showed that not all types of carbonate rocks have the same wettability trend. Specially, the calcites and dolomites seem to show a different behavior and pattern. Also, they show different behavior when we try to alter their wettability from oil-wet to water-wet or gas-wet.
I am looking for the reasons of these differences. What make these two rock types different in terms of wettability and wettability alteration?
Please see the paper by Dag C Standnes and Tor Austad
Wettability alteration in carbonates: Interaction between cationic surfactant and carboxylates as a key factor in wettability alteration from oil-wet to water-wet conditions
Colloids and Surfaces A: Physicochemical and Engineering Aspects
Volume 216, Issues 1–3, 15 April 2003, Pages 243–259
Dear Reza,
If you have to do it with carbonate rocks, so you have to pay attention to how the microstructure is composed of the corresponding rock samples.
Each grain boundary in a fine-grained rock is a discontinuity surface and influences the surface properties significantly. Furthermore fluid inclusions can influence the wettability alteration.
May I show you as an example photomicrographs attached of two different calcite rock types (Fig. 1a and Fig. 1b) with widely varying particle shape and particle size. Now you can imagine that the wettability alteration possibly is greatly influenced by the particle size, the particle shape and the fluid inclusions.
Best regards,
Guenter
Dear Reza,
please find attached some more photomicrographs showing the differences in the microstructure of undeformed calcite rock, deformed calcite rock and deformed dolomite rock. In any case, we must distinguish carefully between intracrystalline porosity (fluid inclusions) and intergranular porosity (grain boundary pores). Furthermore, we must take into account all significant differences in the microstructure of sedimentary and metamorphic carbonate rocks, in any case, it is a very complicated story.
You have my permission to freely use my (unpublished) photomicrographs for your purposes.
Best regards,
Guenter
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