Insights into Nanoscale Wettability Effects of Low Salinity and Nanofluid Enhanced Oil Recovery Techniques

Abstract

In this study, enhanced oil recovery (EOR) techniques—namely low salinity and nanofluid EOR—are probed at the nanometer-scale using an atomic force microscope (AFM). Mica substrates were used as model clay-rich rocks while AFM tips were coated to present alkyl (-CH3), aromatic (-C6H5) and carboxylic acid (-COOH) functional groups, to simulate oil media. We prepared brine formulations to test brine dilution and cation bridging effects while selected concentrations (0 to 1 wt%) of hydrophilic SiO2 nanoparticles dispersed in 1 wt% NaCl were used as nanofluids. Samples were immersed in fluid cells and chemical force mapping was used to measure the adhesion force between polar/non-polar moieties to substrates. Adhesion work was evaluated based on force-displacement curves and compared with theories. Results from AFM studies indicate that low salinity waters and nanoparticle dispersions promote nanoscale wettability alteration by significantly reducing three-phase adhesion force and the reversible thermodynamic work of adhesion, also known as adhesion energy. The maximum reduction in adhesion energy obtained in experiments was in excellent agreement with existing theories. Electrostatic repulsion and reduced non-electrostatic adhesion are prominent surface forces common to both low salinity and nanofluid EOR. Structural forces are complex in nature and may not always decrease total adhesion force and energy at high nanoparticle concentration. Wettability effects also depend on surface chemical groups and the presence of divalent Mg2+ and Ca2+ cations. This study provides fresh insights and fundamental information about low salinity and nanofluid EOR while demonstrating the application of force-distance spectroscopy in investigating EOR techniques.

Preparation of SiO2-Fluorinated Acrylate Polymer Nanoemulsions (SCFs) and Their Application as Depressurization and Injection Treatment Agents

“…The adhesion resistance of the fluid in the porous medium increases, forming water boundary layers, reducing permeability, increasing water injection pressure, and ultimately hindering injection and reducing oil recovery . The wettability of a rock surface controls the distribution of fluids in pore spaces in rocks. , Wettability is considered the main parameter governing enhanced oil recovery (EOR). − If a rock surface is hydrophobic, liquid retention in a porous medium and adhesion resistance are decreased, leading to faster water flow, the injection volume is increased and the injection pressure is reduced to a certain extent . Therefore, the key to solving injection problems is to change the wettability of reservoirs.…”

Mathematical Modeling and Pilot Test Validation of Nanoparticles Injection in Heavy Hydrocarbon Reservoirs

“…On the other hand, when oil droplets are attached to the surface, nanoparticles increase the disjointing pressure because they can be located in their surrounding region. Afekare et al [23,24] employed atomic force microscopy to investigate the oil release mechanisms when SiO 2 nanoparticles are injected in a clay-rich surfaces. The authors found a significant reduction in the adhesion force and adhesion energy: the wettability alteration was controlled by the reduction in nonelectrostatic and interaction force and increasing of the electrostatic repulsion force.…”

Visualizing and Quantifying Wettability Alteration by Silica Nanofluids

“…Previously, atomic force microscopy (AFM) with a sharp solid tip has been used to probe properties of rock surfaces relevant to the oil industry, including their topography as well as mechanical and chemical properties. , The AFM tip can also be functionalized with different organic groups (chemical force microscopy) to mimic the interactions between different oil components and the solid substrate. ,− Intermolecular forces and the adhesion between the chemically modified tips and substrate can be measured with piconewton resolutions, and wettability alterations can be resolved spatially with submicrometer resolutions by using this technique. Chemical force microscopy with its solid tip cannot, however, fully capture the interactions of a liquid droplet with a solid substrate.…”