Some of the advantages of the simultaneous use of surfactants and nanoparticles in enhanced oil recovery (EOR) processes are the increase in the efficiency of injection fluid for sweeping, the reduction of adsorption of the surfactant onto the reservoir rock, the alteration of wettability, and the reduction of water/crude oil interfacial tension (IFT). However, a large amount of nanoparticles required in chemical EOR processes might limit their application. Therefore, the main objective of this work is to synthesize, characterize, and evaluate magnetic iron core–carbon shell nanoparticles that can be recovered and to study their impact on the reduction of surfactant adsorption on the porous media and oil recovery at reservoir conditions. The additional benefit of the proposed method is that these nanoparticles can be recovered and reused after the application because of their magnetic properties. The magnetic iron core–carbon shell nanoparticles were obtained following a new one-pot hydrothermal procedure and were carbonized at 900 °C using a teflon-lined autoclave. The core–shell nanoparticles were characterized using scanning electron microscopy, dynamic light scattering, N2 physisorption at −196 °C, X-ray diffraction, X-ray photoelectron spectroscopy (XPS), and magnetometry measurements. The magnetic iron core–carbon shell nanoparticles with an average particle size of 60 nm were obtained. The XPS spectrum corroborated that magnetic Fe(0) of the core was adequately coated with a carbon shell. The IFT was measured using a spinning drop tensiometer for a medium viscosity crude oil and a surfactant mixture. The minimum IFT reached was approximately 1 × 10–4 mN m–1 at a nanoparticle concentration of 100 mg L–1. At this concentration, the dynamic adsorption tests demonstrated that the nanoparticles reduce 33% the adsorption of the surfactant mixture in the porous media. The simultaneous effect of core–shell nanoparticles and the surfactant mixture was evaluated in a displacement test at reservoir conditions obtaining a final oil recovery of 98%.

The main objective of this study is to evaluate the effect of the preparation of the nanofluids based on the interactions between the surfactants, nanoparticles, and brine for being applied in ultra-low interfacial tension (IFT) for an enhanced oil recovery process. Three methodologies for the addition of the salt–surfactant–nanoparticle components for the formulation of an efficient injection fluid were evaluated: order of addition (i) salts, nanoparticles, and surfactants, (ii) salts, surfactants, and then nanoparticles, (iii) surfactants, nanoparticles, and then salts. Also, the effects of the total dissolved solids and the surfactant concentration were evaluated in the interfacial tension for selecting the better formulation of the surfactant solution. Three nanoparticles of different chemical natures were studied: silica gel (SiO2), alumina (γ-Al2O3), and magnetic iron core–carbon shell nanoparticles. The nanoparticles were characterized using dynamic light scattering, zeta-potential, N2 physisorption at −196 °C, and Fourier transform infrared spectroscopy. In addition, the interactions between the surfactant, different types of nanoparticles, and brine were investigated through adsorption isotherms for the three methodologies. The nanofluids based on the different nanoparticles were evaluated through IFT measurements using the spinning drop method. The adsorbed amount of surfactant mixture on nanoparticles decreased in the order of alumina > silica gel > magnetic iron core–carbon shell nanoparticles. The minimum IFT achieved was 1 × 10–4 mN m–1 following the methodology II at a core–shell nanoparticle dosage of 100 mg L–1.

In this study, a set of advanced characterization techniques were used to evaluate the morphological, structural, and thermal properties of a novel molecular hybrid based on silica nanoparticles/hydrolyzed polyacrylamide (CSNH-PC1), which was efficiently obtained using a two-step synthetic pathway. The morphology of the nanohybrid CSNH-PC1 was determined using scanning electron microscopy (SEM), dynamic light scattering (DLS), and nanotracking analysis (NTA) techniques. The presence of C, N, O, and Si atoms in the nanohybrid structure was verified using electron dispersive scanning (EDS). Moreover, the corresponding structural analysis was complemented using powder X-ray diffraction (XRD) and attenuated total reflection-Fourier transform infrared spectroscopy (ATR-FT-IR). The covalent bond between APTES-functionalized SiO2 nanoparticles (nSiO2-APTES), and the hydrolyzed polyacrylamide (HPAM) chain (MW ≈ 20.106 Da) was confirmed with high-resolution X-ray spectroscopy (XPS). Finally, the thermal properties of the nanohybrid were evaluated by using thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). The results showed that the CSNH-PC1 has a spherical morphology, with sizes between 420–480 nm and higher thermal resistance compared to HPAM polymers without modification, with a glass transition temperature of 360 °C. The integration of these advanced characterization techniques implemented here shows promising results for the study and evaluation of new nanomaterials with multiple applications.

Polymer flooding represents the most common chemical enhanced oil recovery (CEOR) method used at commercial scale. In this process, the polymeric solutions (generally hydrolyzed polyacrylamide - HPAM) are injected to improve the oil/water mobility ratio (M). However, due to mechanical, chemical, bio, and thermal degradation, polymer viscosity losses can occur, causing a negative impact on oil sweep efficiency. In this case, biopolymers seem to be promising candidates in EOR applications with special structural characteristics, which result in excellent stability in harsh environments with high temperatures, ionic forces, and shear stresses. This paper presents the laboratory evaluation of Scleroglucan (SG) and a commercial sulfonated polyacrylamide (ATBS) in synthetic brine, representative of a Colombian heavy-oil field. The effects of ionic strength, pH, temperature, and shear degradation effects on polymer viscosity were also evaluated. For SG, the results reflect its tolerance to high salinities (0-5%wt), ionic strengths (Na+, K+, Ca2+, and Mg2+), shear rates (0-300,000 s-1), temperatures (30, 50, 80 and 100 °C), and pH variations (3-10). The biopolymer was capable of preserving its viscous properties and stability after of the effect of these variables. Finally, the target viscosity (set as 17 cp) was achieved with a lower concentration (2.7 times) than the ATBS polymer tested.

This paper presents a methodology for the selection of the enhanced oil recovery technologies that better applies to some group of fields using screening criteria. The methodology has been integrated in a software in order to make repetitive analysis in an easier way, and has been applied for identifying the technologies whit higher technical potential of application in the Colombian Fields which have the biggest amount of oil in place (approximately 80%). The methodology incorporates oil and rock properties and the reservoir current conditions, besides the specific knowledge of the reservoir generalities and history. In some Colombian fields, processes that use water, gas or steam have been applied; additionally, some other projects using water, gas, chemicals and air are in a design stage at this moment, however, more than 90% of the approximately 280 Colombian fields are still in primary recovery. This is one of the main reasons for having an oil average recovery factor of about 21%, and it also states the need of using methodologies that allow identifying the best investment options. The technologies considered in this analysis were: water injection, lean gas, rich gas, N 2 , WAG, CO 2 (miscible and immiscible), polymer, surfactant -polymer, steam (cyclic and continuous) and some others such as CHOPS, VAPEX, WET VAPEX, SAGD, in situ combustion and electromagnetic heating.The application of the methodology presented in this study allowed to identify the enhanced oil recovery technologies with higher potential for being applied in the Colombian fields with biggest amount of oil in place; it also generated a guide for the construction of every analyzed field development plan, which is presented as an example for the Cocorná heavy oil field.The subject treated in this paper is more important for companies that own an important number of fields, and need to identify those with better characteristics for enhanced oil recovery projects in a quick and easy way; however, it is also very useful for companies that are beginning to develop any specific field.