Wettability Alteration of Sandstone Cores by Alumina-Based Nanofluids

Abstract

Wettability alteration can occur at different stages during the producing life of a reservoir. Oil recovery from oilwet reservoirs can significantly be increased by altering its wettability from an oil-wet to a strongly water-wet condition. Chemical agents such as surfactants are known as wettability modifiers in oil-wet systems. More recently, nanofluids prepared by dispersing nanoparticles in several liquid agents have been considered as potential wettability modifiers. In this work, the effectiveness of alumina-based nanofluids in altering the wettability of sandstone cores with an induced oil-wet wettability was experimentally studied. Eight nanofluids with different nanoparticles concentration, ranging from 100 ppm to 10000 ppm, were prepared by dispersing alumina nanoparticles in an anionic commercial surfactant. The effect of nanofluids on wettability alteration was investigated by contact angle and imbibition tests, and it was shown that designed nanofluids could significantly change the wettability of the sandstone cores from a strongly oil-wet to a strongly water-wet condition. Imbibition tests also allowed identifying the effect of nanoparticles concentration on the suitability of the treatment for enhancing the imbibition process and restoring the original core wettability. Results showed that the effectiveness of the anionic surfactant as wettability modifier could be improved by adding nanoparticles in concentrations lower or equal than 500 ppm. The best performance was achieved when a concentration of 100 ppm was used. Additionally, a core displacement test was carried out by injecting in a sand pack a nanofluid prepared by dispersing alumina nanoparticles in distillated water. The treatment was effective in altering the sand pack wettability from an oil-wet to a strongly water-wet condition as indicated by a significant reduction in the residual water saturation and a displacement to the right of the oil relative permeability curve and the crossover point.

Application of Nanoparticles in Enhanced Oil Recovery: A Critical Review of Recent Progress

“…Currently, there are three main experimental methods that are commonly used by researchers for wettability measurement: the contact angle method, the Amott test and the core displacement test [37][38][39][40][41]. Among them, the contact angle method is the most universal used approach to determine wettability.…”

“…The core displacement test also can be used to determine wettability alterations by comparing the changes in residual water saturation (Swr), oil relative permeability (kro) and the point where the water and oil relative permeabilities are equal (crossover point) before and after nanofluid treatment. Based on Craig's rules, if the Swr increases, the kro and the crossover point move to the right after nanofluid treatment, the wettability is changed from an oil-wet to a water-wet condition ( Figure 9) [37]. Relative permeability curves.…”

“…The symbols are experimental data. The notation AT and BT indicates that measurements were carried out after or before nanofluid treatment [37].…”

“…Secondly, the use of Al 2 O 3 NPs with an anionic surfactant can change rock wettability from oil-wet to water-wet and also increase ultimate oil recovery [37]. Recently, Mohajeri et al [127] also found that C12TAB (a cationic surfactant)/ZrO 2 NPs could alter the wettability to a water-wet condition.…”

Improving the microscopic sweep efficiency of water flooding using silica nanoparticles

“…Based on previous studies, reduction of the interfacial tension between oil and water and alteration of the rock wettability toward water-wet condition can be identified as the chief mechanisms of improving oil recovery by silica nanoparticle (Ayatollahi et al 2012;Roustaei et al 2012;Torsater et al 2012;Giraldo et al 2013). In other words, oil recovery factor can be improved by nanoparticles through various mechanisms from IFT reduction to decreasing the oil viscosity to wettability alteration and improving the mobility ratio (Khademolhosseini et al 2015).…”