| WANG Shizhen,WU Lirong,HONG Lanlan,LI Xiaoling,WU Yuguo,DING Yi,LI Ting.Experimental Analysis of Effect of Inorganic Salts on Oil-water Interface of Sodium Dodecyl Benzene Sulfonate System Based on Molecular Dynamics[J],54(10):256-265 |
| Experimental Analysis of Effect of Inorganic Salts on Oil-water Interface of Sodium Dodecyl Benzene Sulfonate System Based on Molecular Dynamics |
| Received:July 30, 2024 Revised:November 27, 2024 |
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| DOI：10.16490/j.cnki.issn.1001-3660.2025.10.021 |
| KeyWord:inorganic salt molecular dynamics surfactant SDBS oil-water interface emulsion viscosity reduction |
| Author | Institution |
| WANG Shizhen |
College of Petroleum Engineering, Liaoning Petrochemical University, Liaoning Fushun , China |
| WU Lirong |
Sinopec Senmei Fujian Petroleum Co., Ltd., Fuzhou , China |
| HONG Lanlan |
Sinopec Sales Co., Ltd., Fujian Quanzhou Petroleum Branch, Fujian Quanzhou , China |
| LI Xiaoling |
College of Petroleum Engineering, Liaoning Petrochemical University, Liaoning Fushun , China |
| WU Yuguo |
College of Petroleum Engineering, Liaoning Petrochemical University, Liaoning Fushun , China |
| DING Yi |
College of Petroleum Engineering, Liaoning Petrochemical University, Liaoning Fushun , China |
| LI Ting |
College of Petroleum Engineering, Liaoning Petrochemical University, Liaoning Fushun , China |
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| Abstract: |
| This paper aims to provide a more valuable reference method for safe and economic transportation of heavy oil, which can better improve the viscosity reduction effect and enhance its stability at normal temperature. Aiming at the problem of safe and economic transportation of heavy oil, which has been focused on by many scholars, the synergic effect of inorganic salts on the oil-water interface of heavy oil emulsion during the viscosity reduction process of heavy oil was specifically studied. According to the theory of molecular dynamics, various molecular models were obtained by MS. The oil model was built according to the four components in the heavy oil. After optimization and annealing treatment, the oil model and 996 water molecules were assembled together (8 SDBS molecules and inorganic salts were randomly dispersed within the water molecular box). A time step of 1 fs was selected, MD simulation of 500 ps under canonical ensemble (NVT) was performed, and then analysis was performed using the Forcite module. The RDF curve was used to analyze the microstructure information of particles in solution when different inorganic salt molecules (species and mass fraction) were added, the influence of NaCl on the stability of the oil-water interface was determined by EIF. The effects of various types of inorganic salts (NaCl, MgCl2 and CaCl2) on solution fluidity were analyzed based on MSD and diffusion coefficient (D), followed by an analysis of how inorganic salts affected the thickness of the oil/water interface using concentration distribution curves for simulated oil and water molecules along the Z-axis direction. In the verification part of the experiment, the oil and the emulsifier system aqueous solution were placed in a jacketed beaker (the emulsifier system was composed of an optimal mass concentration of 1.25% SDBS and inorganic salts). The heavy oil emulsion was preheated in a constant-temperature water bath at 25 ℃, then stirred with a multi-function agitator (HJ-5) at 400 r/min. After the heavy oil emulsion was obtained, the apparent viscosity was measured with a digital viscometer (DV-T2). The interfacial tension between the surfactant SDBS compound inorganic salt system and Liaohe's heavy oil was measured by a rotating drop interfacial tensiometer (JJ2000B). In the simulation, the interface thickness of the three systems (NaCl, MgCl2, and CaCl2) was 9.765, 10.793 and 11.307 Å, and the diffusion coefficients (D) of the three systems was (5.83, 5.13 and 4.81)×10−5 cm2/s. Experiments confirmed that inorganic salts could enhance the reduction of viscosity and stability of heavy oil emulsion under low concentration conditions. The viscosity increase of NaCl, MgCl2, and CaCl2 systems after 2 hours was 46.0, 14.1 and 6.6 mPa.s respectively. Among them, Ca2+ had the most significant effect, which could enhance various properties of surfactants. When the mass concentration of all three inorganic salts is 0.1%, the promoting effect of NaCl is poor at the same concentration, but increasing the concentration can further improve the synergistic effect. When 1.5% NaCl is added, the viscosity of heavy oil is 15 mPa.s, and the viscosity only increases by 11 mPa.s after 2 hours. However, increasing the concentration of CaCl2 and MgCl2 inhibits the emulsification effect of SDBS, and at the same time, the solution salts out, which has an adverse effect on the viscosity reduction of heavy oil. |
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