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.

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The deposition of asphaltenes is one of the most difficult problems to overcome in oil production and processing. The presence of asphaltenes in crude oil, and consequently, the adsorption and deposition of asphaltenes on the rock surfaces, affects the rock properties, such as porosity, permeability, and wettability. This study aims at analyzing the effect of the chemical nature of 12 types of nanoparticles on asphaltenes adsorption; hence, the delay or inhibition of deposition and precipitation of asphaltenes on porous media under flow conditions at reservoir pressure and temperature were investigated. The adsorption equilibrium of asphaltenes onto nanoparticles was effectively achieved within relatively short times (approximately 2 min), which indicates the promising nature of adsorbents for delaying the agglomeration and inhibiting the precipitation and deposition of asphaltenes. The adsorption equilibrium of asphaltenes for the nanoparticles was determined using a batch method in the range 150–2000 mg/L. The equilibrium adsorption data were fit to both the Langmuir and Freundlich models. Additionally, in this study, the transport of nanoparticles in a porous media at a typical reservoir pressure and temperature was investigated. As a result, the use of nanoparticles allowed the system to flow successfully, which demonstrated the inhibition of precipitation and deposition and the enhanced perdurability against asphaltene damage in the porous media.

This study is a continuation of our previous works on the use of metal-based nanoparticles for the adsorption of asphaltenes and its subsequent catalytic thermal decomposition. In this study, we evaluated the effects of asphaltene aggregation on the adsorption process and the subsequent catalytic oxidation using fumed silica and nanoparticles of NiO and/or PdO supported on fumed silica. Adsorption isotherms were constructed through batch adsorption experiments at 25°C by using mixtures of n-heptane and toluene in amounts of 0, 20 %v/v (heptol 20) and 40 %v/v (heptol 40) of n-heptane to obtain different aggregate sizes of asphaltenes. Subsequently, asphaltene oxidation in the presence and absence of the nanoparticles was carried out in a TGA/FTIR system to investigate the impact of adsorbed asphaltene aggregates on the catalytic activity of the selected nanoparticles. The adsorption isotherms were described by the solid-liquid equilibrium (SLE) model, and the catalytic behavior of the nanoparticles was compared based upon the trend of effective activation energies using the isoconversional method of Ozawa−Flynn−Wall (OFW). The results showed that the K parameter of the SLE model for both nanoparticles followed the trend of heptol 40 > heptol 20 > toluene, indicating that as the amount of precipitant in the solution increases, a higher degree of asphaltene self-association on the active site of the catalysts is found. On the other hand, the H parameter revealed higher adsorption affinities as the nheptane in the solution increased. However, when different adsorbents were compared at a fixed asphaltene concentration from the same solution it was found that the use of functionalized nanoparticles led to a lower degree of asphaltene self-association and a higher affinity. A correlation between the effective activation energies from the OFW model and the SLE parameters was developed, finding that for a fixed adsorbent, the E α increases as the affinity and the degree of self-association of asphaltenes increases. However, when the same asphaltenes were compared using different adsorbents, it was observed that the E α increases as the affinity decreases and the degree of asphaltene selfassociation increases. Consequently, this work shows the effect of the adsorption process on the catalytic activity of the nanoparticles. The reported results should give a better context for the use of such nanoparticles for the upgrading of heavy and extra-heavy oil.

The aim of this study is to analyze the effect of temperature and NiO content on the asphaltene uptake by a hybrid nanomaterial composed of nickel oxide nanoparticles supported on a nanoparticulated matrix of silica gel. The silica gel nanoparticles were synthesized by sol−gel method. The silica-supported nanomaterial was prepared by an incipient wetness technique. At constant temperature, adsorption of asphaltenes onto the hybrid nanomaterials increased with increasing its nickel oxide content. Regardless of the asphaltene concentration, asphaltene uptake by the hybrid nanomaterials decreased with increasing temperature. Experimental data on asphaltene sorption isotherms were adequately adjusted by the Freundlich model. The calculated thermodynamic properties for the sorption of asphaltenes onto the nanoparticulated-materials confirmed the spontaneity and exothermic nature of this process.