Chapter 4
wettability of kaolinite from water-wet to more oil-wet. Kaolinite is partially
positively charged. The positively-charged sites can adsorb anionic naphthenate
and become oil-wet.
Figure 4.3 Water-wet fraction of kaolinite in toluene-brine mixture with 1.0 %
kaolinite
The third bar is water-wet fraction (30%) in the sample with 100 ppm sodium
naphthenate adding 0.6 mM NaOH at pH 9.0. Compared with the second bar,
water-wet fraction increases. Adding NaOH can convert some of the positively-
charged sites to negatively-charged sites. This can reduce the adsorption of
naphthenate on kaolinite surface and make kaolinite more water-wet.
The last bar is water-wet fraction (38%) in the sample with 100 ppm sodium
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