Synergetic adsorption of asphaltenes and oil displacement surfactants on the oil-water interface: Insights on stabilization mechanism of the interfacial film

Insights into Molecular Dynamics and Oil Extraction Behavior of the Polymeric Surfactant in a Multilayered Heterogeneous Reservoir

Interlayer heterogeneity, an inevitable and complex challenge during water flooding, seriously constrains the spread of the sweep region and oil recovery enhancement in multilayered heterogeneous reservoirs. To overcome this challenge, a novel polymeric surfactant, having an excellent performance in the reduction of interfacial tension (IFT) and the increase of viscosity of displacing fluid, is applied for enlarging the sweep resonance and increasing the oil washing efficiency. Through the molecular dynamics (MD) simulation, the molecular distributing mechanisms of the polymeric surfactant at the oil-water interface are analyzed to provide the theoretical basis for explaining the microscopic mechanism of oil extraction. To directly reflect the microscopic behavior of oil extraction, multiple transparent sand-packed models are designed to investigate the flowing behavior of different fluids and the extracted mechanisms of the remaining oil in both pore and macroscales. The multilayered heterogeneous reservoirs consisting of high-, moderate-, and low-permeability layers are fabricated to represent a heterogeneous characteristic. The recognition from the visual experiment and MD simulation can study the performance control, the extracting performance of the remaining oil, and the expression of the displacing front from different perspectives. The results from MD simulation demonstrate that the polymeric surfactant can promote the disintegration of the remaining oil and enhance its mobility. The experimental results indicate that the sweep efficiency is restricted by viscous fingering and tongue advance. Through the analysis of mathematical models, the rising mobility ratio and the location of the displacing front have a strong positive relationship with viscous fingering and tongue advance, which can reasonably explain the plugging performance of the polymeric surfactant, greatly improving the sweeping effect of the whole reservoir. Moreover, the Marangoni effect generated by the IFT gradient can induce the transformation of interfacial energy to displacement kinetic energy by the emulsification of the oil-water interface so that the remaining oil in the blind-end pore can be effectively extracted. However, by comparing data from image quantification techniques and production dynamic performance, the sweep efficiency (484%) was significantly greater than that of oil recovery (300%), demonstrating that the expanded sweep effect still plays a dominant role in the extraction of remaining oil after polymeric surfactant flooding. This study provides a novel plugging and effective washing agent that is expected to be an excellent and comprehensive method for solving the problem of low oil recovery in multilayered heterogeneous reservoirs.

Molecular Dynamics Simulation of the Effects of Complex Surfactants on Oil-Water Interaction and Aggregation Characteristics at the Interface

In response to the problem of complex interaction between oil and water in the oil-water interface, especially heavy oil and water, this study investigated the effects of complex surfactants on the interaction of two phases and their aggregation characteristics by molecular dynamics simulation. The results showed that increasing the content of sodium lauryl polyether carboxylate (AEC-9Na) was beneficial to the coordination between it and alkyl glycoside (APG-10), improved the interfacial activity, and enhanced the interfacial stability of the composite system, and the best effect was achieved when AEC-9Na:APG-10 = 8:2. The thickness of the oil and water film on the oil-water interface was irregular. When the concentration of AEC-9Na was lower than that of APG-10, the total thickness of the interfacial film (ttotal) first increased. When the content of AEC-9Na is higher, a large number of sodium ions were adsorbed near the -COO- group of AEC-9Na, which will polarize out of the hydration layer structure and attract water molecules from the second hydration layer on the heavy oil surface to the first hydration layer through electrostatic interaction. Then, the thickness of the interface film was compressed, and the interface film was reduced. When the ratio increased to 10:0, the oil and water phase competed to adsorb surfactant molecules, and the headgroup tended to lay on the interface. Moreover, the hydrophilicity of the surfactant layer was weakened, and the thickness of the water film decreased. The distribution of surfactant was looser than 8:2, the light components of heavy oil molecules (saturated and aromatic hydrocarbons) entered the gap between surfactants in large quantities, and the hydrophobic tail chain tended to be laid on the oil-water interface. The oleophilicity of the surfactant layer increased, and the thickness of the oil film remarkably increased, so the total thickness of the interface film increased again.

A Review of Oil-Solid Separation and Oil-Water Separation in Unconventional Heavy Oil Production Process

Unconventional heavy oil ores (UHO) have been considered an important part of petroleum resources and an alternative source of chemicals and energy supply. Due to the participation of water and extractants, oil-solid separation (OSS) and oil-water separation (OWS) processes are inevitable in the industrial separation processes of UHO. Therefore, this critical review systematically reviews the basic theories of OSS and OWS, including solid wettability, contact angle, oil-solid interactions, structural characteristics of natural surfactants and interface characteristics of interfacially active asphaltene film. With the basic theories in mind, the corresponding OSS and OWS mechanisms are discussed. Finally, the present challenges and future research considerations are touched on to provide insights and theoretical fundamentals for OSS and OWS. Additionally, this critical review might even be useful for the provision of a framework of research prospects to guide future research directions in laboratories and industries that focus on the OSS and OWS processes in this important heavy oil production field.

Preparation of a demulsifier for oily wastewater using thorn fir bark as raw materials via a hydrothermal and solvent-free amination route

In current work, a TB-EDA demulsifier for disposing oily wastewater was prepared using thorn fir bark (TB) as starting materials via a hydrothermal and solvent-free amination route. Field emission scanning electron microscope (FE-SEM), energy dispersive X-ray spectrometer (EDS), and Fourier transform infrared spectroscope (FT-IR) were employed to characterize the TB-EDA demulsifier. Three-phase contact angle (CA), interfacial activity, formation of interfacial film (FIF), coalescence time of droplets (CTD), dynamic interfacial tension (IFT), and Zeta potential were carried out to study the possible demulsification mechanism. Bottle test was performed to investigate the effect of the TB-EDA dosage, salinity, and pH value on the demulsification performance at room temperature. Light transmittance (D_L) and oil removal rate (D_R) of separated water were 94.7% and 97.2%, respectively, with 100 mg/L of TB-EDA demulsifier in oily wastewater at room temperature. In addition, the TB-EDA demulsifier has an excellent salt tolerance even at the salinity of 50,000 mg/L. The corresponding D_L and D_R could reach 99.8% and 99.9%, respectively.

Nano-modification of carboxylated polyether for enhanced room temperature demulsification of oil-water emulsions: Synthesis, performance and mechanisms

Oil-water emulsions separation is frequently required considering the production and environmental issues. Herein, a nano-modification strategy has been proposed for carboxylated poly(propylene oxide)-poly(ethylene oxide) block polyether (mANP) using epoxy-functionalized magnetic nanoparticles (Fe₃O₄@SiO₂-GPTMS), achieving the construction of a highly efficient demulsifier (M-mANP). Bottle tests showed that M-mANP could separate over 98.5% of water from the asphaltene-stabilized water-in-oil (W/O) emulsion at mANP concentration of 150 ppm within 2 min at room temperature. The demulsification efficiency for crude oil-in-water emulsion was nearly 100%. According to interfacial tension and wettability tests, the nano-modification endows M-mANP with good amphiphilicity and high interfacial activity, which enables M-mANP to rapidly adsorb at the oil-water interface. Molecular dynamics simulation shows that abundant oxygen-containing groups (hydroxyl, ether bond, ester and carboxyl groups, Fe-O and Si-O bond) in M-mANP could strengthen the interaction with water, facilitating the replacement of asphaltene molecules at interfacial film. Observation of demulsification process by microscope reveals that the nano-size promotes M-mANP to bridge small dispersed droplets, enhancing the flocculation and coalescence of droplets. The nano-modified carboxylated polyether with outstanding demulsification ability shows a promising application for the treatment of different oil-water emulsions.

Effect of Oil-Displacing Agent Composition on Oil/Water Interface Stability of the Asphaltene-Rich ASP Flooding-Produced Water

In this work, the effect of oil-displacing agent composition on oil/water interface stability of the asphaltene-rich alkali-surfactant-polymer (ASP) flooding-produced water was systematically investigated, especially from the perspective of the interaction between oil displacement agents and asphaltene at the oil/water interface. Primarily, adsorption behavior of the artificial and natural interfacial substances (oil displacement surfactant and asphaltenes) on the oil/water interface was investigated by molecular dynamics simulation. The oil displacement surfactant and asphaltenes formed a cross-linked and compact interfacial film structure, which significantly enhanced the interface stability; the more the oil displacement surfactants adsorbed on the interface, the more stable is the cross-linked structure formed between them and asphaltenes. Then, the interfacial property variations that are originating from the interactions differences between oil displacement agents and asphaltenes were monitored via interfacial tension, zeta potential, and interfacial film rheology tests. Moreover, the effect of oil displacement agent concentrations on the interfacial film thinning and rupture kinetic behavior was further investigated. Finally, cream experiments were conducted to verify the effect of oil displacement agent composition on the oil/water separation efficiencies of asphaltene-rich ASP flooding-produced water. When 5% asphaltenes was added, the creaming oil removal rate reduced from 90.0 to 85.3% at 19 h. The interactions between asphaltenes and oil displacement agents immensely enhance the oil/water interfacial film strength and impede the oil/water separation process.