The precipitation and deposition of asphaltenes is a primary problem related to the processing, transportation and production of oil. Flocculation of asphaltene aggregates is likely to occur during the production and processing of crude oil. Recently, it has been shown that nanotechnology in the form of nanoparticles is useful for the inhibition or prevention of asphaltene formation damage. Although it is well known that the adsorption of asphaltenes on the nanoparticle surface would reduce the capacity of these asphaltic compounds to interact with each other, limited studies have been performed regarding the processes and the mechanisms associated with the effect of nanoparticles on the inhibition of the formation damage due to asphaltenes. To better understand this phenomenon from a mathematical approach, a population balance model (PBM) is proposed to describe the kinetics of asphaltene flocculation-fragmentation in the presence of nanoparticles. The model assumes that asphaltenes in the presence of a shear rate are related to the aggregation and fragmentation phenomena and includes a term related to the asphaltene adsorption on nanoparticles. An adsorption kinetic term was introduced into the model using the double exponential model. Experimental data of the kinetics of asphaltene aggregation were obtained by Dynamic Light Scattering (DLS) measurements at a fixed initial asphaltene concentration of 1000 mg/L and with different Heptol mixtures. In this study, commercial silica, γ-alumina and magnetite nanoparticles were used as adsorbents to study the effect of the chemical nature of the nanoparticles on the inhibition of the asphaltene growth and for model validation. Additionally, to demonstrate the versatility of the proposed model, the effect of asphaltene was also evaluated. The obtained results from the proposed population balance model agree well with the experimental data, within an % RSME < 9%.

The main objective of this study is to evaluate the effect of particle size and surface acidity of synthesized silica gel nanoparticles on the inhibition of formation damage caused by asphaltene precipitation/ deposition. Silica gel nanoparticles were synthesized through the sol−gel method, and their characterization was performed via N 2 physisorption at −196 °C, field emission scanning electron microscopy (FESEM), dynamic light scattering (DLS) measurements, and NH 3 temperature-programmed desorption (TPD). The size of the synthesized nanoparticles ranged from 11 to 240 nm. The ability of the nanoparticles to adsorb asphaltenes and to reduce asphaltene self-association was evaluated using batch-mode experiments. The kinetics of asphaltene aggregate growth in the presence and absence of nanoparticles were evaluated using DLS measurements in different Heptol solutions. The smallest nanoparticles (11 nm) had the highest adsorptive capacity for n-C 7 asphaltenes among the nanoparticles studied. Therefore, these nanoparticles were modified using acid, base, and neutral treatments, which showed the following order S11A ≫ S11B ≃ S11N ≃ S11 according to the n-C 7 asphaltene affinity and the reduction of its mean aggregate size in the bulk phase. The surface acidity values obtained through of temperature-programmed desorption test ranged from 1.07 and 1.32 mmol/g. In general, the asphaltene self-association was reduced to a higher degree as the amount of adsorbed asphaltene increased. Additionally, in this study, the performance of a nanofluid treatment was tested under flow conditions in porous media under typical reservoir conditions using the nanoparticles with the best performance in batch-mode experiments. Indeed, nanofluid treatment with silica nanoparticles increased the effective permeability to oil and enhanced the oil recovery with an increase in the recovery factor of 11% under the conditions reported here. This approach has the major benefit of being scalable to a producing field, and the study provides an understanding of the roles of size and surface acidity of silica nanoparticles in the wettability alteration and inhibition of formation damage caused by asphaltenes and their influences on asphaltene aggregate size in the oil matrix and the adsorbed phases.

The primary objective of this study is to show the importance of the adsorption method used in obtaining the nanoparticle dosage for inhibiting/remediating asphaltene-related problems. In this work, two methods for determining the adsorption isotherms for different asphaltenes onto three different types of nanoparticles were evaluated. The adsorption equilibrium of n-C7 asphaltenes was determined using batch-mode adsorption experiments that were performed in two different ways: (i) by exposing a certain mass of nanoparticles in a fixed volume of liquid with a varying initial concentration of asphaltenes and (ii) by exposing a given amount of asphaltenes in a fixed volume of liquid while varying the dosage of nanoparticles. The results obtained using these two methods were sufficient to determine the type I and III adsorption isotherms, respectively. These differences in behavior in adsorption isotherms can be due complexity of the n-C7 asphaltenes, which are self-associative molecules that impact directly the interaction between the adsorbate (i-mers depending on their concentration) and adsorbent. These results were proven through the aggregate size distribution of asphaltenes as estimated by dynamic light scattering (DLS) measurements. The experimental data was well described with the solid–liquid equilibrium (SLE) model. The adsorption isotherms obtained using the second method deviated significantly from those typically reported in the literature. However, this method is a useful tool for determining the required amount of nanoparticles based on the interactions of adsorbate–adsorbate and adsorbate–nanoadsorbent. Indeed, this method is of practical significance because the amount of asphaltenes at reservoir conditions can be considered constant when treatments are performed.

The main objective of this work is to develop a nanofluid based on the adsorption/desorption process of cationic, anionic, and nonionic surfactants onto nanoparticles and its application in enhancing the process of oil recovery. The development of the nanofluids was divided into two experimental routes for understanding the adsorption phenomena of the surfactants (cetyltrimethylammonium bromide (CTAB), sodium dodecyl sulfate (SDS), and polyoxyethylenesorbitan monolaurate (Tween 20)) onto silica nanoparticles (SiO 2 ) by (I) simultaneous addition of nanoparticles and surfactant before micelle formation and (II) the addition of nanoparticles after micelle formation. The adsorption/desorption isotherms for determining the ability of nanoparticles to adsorb surfactants were obtained at 25, 50, and 70 °C using batch-mode experiments. The experimental adsorption isotherms were types I and III depending on the route and the chemical nature of the surfactant and were adequately described by the solid−liquid equilibrium (SLE) model. The amount adsorbed of surfactant onto nanoparticles decreased in the order CTAB > Tween 20 > SDS and was higher for route II than for route I. Meanwhile, the desorption percentages obtained were 2.0, 5.3, and 9.1% for CTAB, Tween 20, and SDS, respectively. The thermodynamic behavior of surfactant adsorption onto SiO 2 nanoparticles suggested that the adsorption was a spontaneous and an exothermic process. From the adsorption/desorption isotherms, a composite nanomaterial for enhancing oil recovery was obtained and was evaluated through interfacial tension (IFT) measurements and displacement tests using a micromodel. The composite material based on nanoparticles−surfactant did not generate a significant effect on interfacial tension compared to the surfactant solution. However, the nanofluid increased the oil recovery up to 240% regarding surfactant flooding.