The name is absent

Chapter 6

layers when partially oil-wet clay solids are present. Increasing pH and adding
silicate can make clay solids more water-wet and the volume of the rag layer
smaller.

Kaolinite with 100 ppm sodium naphthenate in toluene-brine mixture is
chosen as the model system for wettability test. Kaolinite is water-wet in
toluene-brine mixtures. But when sodium naphthenate is added, most of kaolinite
becomes oil-wet. It has been found that the higher the naphthenate concentration,
the lower the water-wet fraction. Wettability of kaolinite can be altered by pH
control, silicate and surfactant. NaOH and silicate can make kaolinite surface
more negative, which results in kaolinite becoming more water-wet. But to reach
water-wet fraction above 70% requires adding NaOH or silicate above pH 10.0.
Adding 366 ppm silicate at pH 10 can get 80% of kaolinite water-wet. CsTAB,
amine oxide DO and betaine 13 with appropriate dosage (5 ppm, 20 ppm and 200
ppm) can make 90% kaolinite water-wet with 100 ppm naphthenate. Much less
CsTAB or amine oxide DO is required compared to betaine. Cationic groups of in
these surfactants can interact with anionic naphthenate can form ion pairs, which
can minimize the adsorption of CsTAB and naphthenate and make kaolinite more
water-wet. Wettability of kaolinite is sensitive to the dosage of CsTAB and amine
oxide. The adsorption of excess cationic groups on kaolinite surface makes

190

<<   203   204   205   206   207   208   209   >>

More intriguing information