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Phenol-formaldehyde resins combined with polymers have a wide range of industrial applications as plugging agents for profile control and enhanced oil recovery. Due to the structural resemblance between lignin and phenol, there are possibilities for environmentally friendly phenol-formaldehyde resin manufacturing. Sulfonated lignin–based phenol-formaldehyde resin was synthesized by partially replacing phenol with lignin, which improved the utilization rate of lignin and achieved the purpose of environmental preservation and resource conservation. Partially hydrolyzed polyacrylamide is the most widely used polymer in chemical methods for enhanced oil recovery. However, the stability of reservoirs with high salt and high temperatures is weak under these conditions. To solve the problem of low oil recovery in high-salt reservoir environments, polymer flooding is adopted, which utilizes high-molecular-weight polymers to raise the viscosity of injected fluids, thereby improving sweep efficiency and altering mobility ratio between oil and injected fluid. We focus on the stability study of different molecular weights partially hydrolyzed polyacrylamide combined with sulfonated lignin – based phenol-formaldehyde resins in metal ions and surfactants. The zeta potential and hydrodynamic diameter of the partially hydrolyzed polyacrylamide – sulfonated lignin – based phenol-formaldehyde resin system in Ca2+ were measured by dynamic light scattering and static light scattering, and the dispersion stability was analyzed. The interfacial energy – modified DLVO theory was introduced to evaluate the stability of its colloidal solution, which made it possible to predict the aggregation behavior of sulfonated lignin – based phenol-formaldehyde resin and the co-migration process of metal cations in real time. [ABSTRACT FROM AUTHOR]

Enhanced oil recovery research focuses on the phenol–formaldehyde resin (PFR) solution (EOR). We studied PFR's morphology and aggregation kinetics at various pH levels. A hydrated layer formed on the surface of PFR as a result of hydrogen bonding between the hydroxyl and phenolic hydroxyl groups and water molecules. We quantitatively quantified the impact of pH on the morphology and aggregation kinetics of PFR by incorporating the hydrated force into the DLVO (Derjaguin Landau Verwey Overbeek) theory. We were able to predict the situation of aggregates plugging into the reservoir by altering the size of PFR aggregates in a capillary. [ABSTRACT FROM AUTHOR]

• A novel surfactant-biopolymer (SP) combined system was successfully developed for heavy oil reservoirs. • The emulsification performance and synergistic mechanisms of SP system were systematically investigated. • The mechanism of SP system for enhancing heavy oil recovery was revealed with dual viscosity reduction and mobility controllability. Surfactant-polymer (SP) combined systems have been proven to be efficient for enhancing heavy oil recovery through in-situ emulsification and water thickening mechanisms due to their dual viscosity reduction and mobility controllability. In this study, 0.1 wt% anionic surfactant (fatty alcohol polyoxyethylene ether sulfate, SC) and 0.05 wt% biopolymer (xanthan gum, XG) were combined to develop a novel SP system (SC-XG). The emulsification properties including stability, droplet morphology and size distribution, as well as oil–water interfacial tension (IFT), rheology were systematically investigated. The results showed that the addition of XG into SC systems could obviously decrease the viscosity ratio of oil to displaced water (μ o / μ d) to 1.42 and simultaneously maintain the high viscosity reduction rate at 94.03 %, which is beneficial for decreasing the mobility ratio of water to oil (M). Besides, the emulsion prepared by SC-XG displayed stronger stability and smaller droplet size compared to those of SC after aging 2 h. Although the addition of XG into SC system could slightly increase the oil–water IFT, the viscosity and viscoelasticity were significantly strengthened and displayed main contributions to the enhancement of emulsion stability. Finally, the sand-pack flooding experiments showed that the optimum SC-XG system could enhance the heavy oil recovery by 20.20 % after brine flooding process, which exhibited dual viscosity reduction and mobility controllability. This study demonstrates the facile design and potential applications of SP system for heavy oil reservoirs. [ABSTRACT FROM AUTHOR]

In recent years, phenol-formaldehyde resin (PFR) as a colloid plugging agent was extensively used in enhanced oil recovery. It has been popularly concerned that the influence of environment on the structure, migration and aggregation behavior of PFR. The classical Derjaguin-Landau-Verwey-Overbeek (DLVO) theory can explain the interaction potential between particles. However, the classical DLVO cannot explain differences when colloids aggregate in the same valence metal cation solution. In this work, the effects of ion specificity of divalent metal cations (i. e., Mg2 + and Ca2 +) on the aggregation rate, fractal dimension, zeta potential and the c ritical c oagulation c oncentration (CCC) of PFR were systematically studied by dynamic light scattering experiment, electrophoretic light scattering and spectral turbidimetry. The experimental results showed that metal cations with poor hydration (i. e., Mg2 +) can promote aggregation more than metal cations with good hydration (i. e., Ca2 +). The hydrated differences of ions can be explained quantitatively by the improved DLVO theory introducing Lewis acid-base interaction. This result revealed the important significance of ion specificity in the aggregation behavior of PFR colloids, and made it possible to understand the co-transport process of PFR aggregates and metal cations in reservoirs. Thus, it is possible to precisely control the aggregation rate and the fractal dimension of PFR aggregates. [Display omitted] • Phenol-formaldehyde resin was prepared by adding NaOH step by step. • The aggregation kinetics of Phenol-formaldehyde were studied by turbidities. • We studied morphology of aggregates of Phenol-formaldehyde by fractal dimension. • Based on the DLVO theory, We proposed the interface energy of the colloid. • We explained differences of divalent ions by Lewis acid-base interaction. [ABSTRACT FROM AUTHOR]