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|a Reservoir wettability is depending firmly on the existence of polar components (acids or bases) which are soluble in crude oil and their interaction on the solid surfaces. Wettability alteration by chemical agents such as surfactant and nanoparticles is seen to be one of the realistic methods to modify the wettability of carbonate rock from oil-wet to water-wet conditions. An experimental study of wettability changes upon exposure to cetyltrimethyl ammonium bromide (CTAB) surfactant and nanoparticles dispersed in CTAB has been conducted. Besides that, the stability of the nanoparticles colloidal was also determined by sedimentation and transport test. In addition to that, interfacial tension (IFT) before and after addition of nanoparticles into the system was also determined. Finally, core displacement test was accomplished to determine the effectiveness of nanoparticles in displacing the remaining oil trapped in the reservoir. It was found that CTAB could alter the wettability of oil-wet dolomite to water-wet and addition of nanoparticles has enhanced the contact angle reduction. Al2O3 nano solution was more stable than ZrO2 and about 55% of Al2O3 and 52.5% of ZrO2 could be recovered from the transport test. The IFT of the system was 0.077 mN/m and has reduced after addition of nanoparticles into the system. The reduction of IFT due to Al2O3 was greater as compared to ZrO2. Oil recovery by water flooding was 55%, 62.7% and 56% for sand packs 1, 2, and 3 respectively. However, after injection of two pore volumes of Al2O3, ZrO2 nano solutions, and CTAB surfactant additional 20%, 16.7% and 14.1% of oil were recovered from sand packs 1, 2 and 3, respectively due to wettability alteration. As the conclusion, favourable wettability must be obtained in order to produce more oil especially in carbonate and mature reservoirs.
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