Developing New Recyclable and pH-Sensitive Amphiphile for Heavy Oil Emulsion and Demulsification: A Molecular Dynamics Study

  • Hao Li
  • Caili Dai
  • Xuepeng Wu
Conference paper
Part of the Springer Series in Geomechanics and Geoengineering book series (SSGG)


We report a long-chain N-alkyl-N, N-dihydroxyethylammonium salt (ADHA) that can be reversibly transformed into charged surfactants by decreasing pH, thereby stabilizing(or destabilizing) water/oil emulsions. As the conventional oil reserves in the world continue to decline, the immense deposits of heavy crude oil attract much attention. A growing number of heavy oil reservoirs are being proven and developed. However, heavy oil’s recovery and pipeline transport pose new challenges due to its high viscosity. The emulsion of heavy oil by surfactant floods is able to lower the viscosity but consequently leads to oil–water separation problem. Therefore, the application of this technique will benefit from an efficient, rapid method of demulsification at specially desired stage, which raises stringent requirements to the surfactants. The increase of the pH reverses the reaction, deprotonates the surfactants into uncharged tert-ammonia (ADHA), and destabilizes the emulsion. In addition, the introduction of two hydroxyls in the head groups reduces the lipophilic of the ADHA. Hence, it is inclined to flocculate in water when the base is added and it is simple to realize the recycle of the surfactant. MD simulations are used to study the mechanisms of this novel surfactant. Demulsification was studied in a beaker; the emulsion separates into two layers within 3 min, revealing the ADHA’s function as a demulsifier. Aiming for deeper insights into the mechanisms of the transformation of ADHA, using MD simulation tools, we studied the behavior and properties of ADHA at the oil–water interface. Computational results suggest cohesive bindings with experimental outcomes and also give qualitative and quantitative explanations at molecular level. In summaries, these emulsion–demulsification processes suggest that the switchable surfactants are potentially useful for heavy oil production and pipeline transports.


pH-Sensitive amphiphile Heavy oil emulsion Molecular dynamics study 



The work was supported by the National Natural Science Foundation of China (21303268, U1663206), the National Science Fund for Distinguished Young Scholars (51,425,406), the Chang Jiang Scholars Program (T2014152).


  1. 1.
    Liu G (1995) Heavy oil emulsification viscosity reduction technologies. Spec Oil Gas Reservoirs 2(1):57–61Google Scholar
  2. 2.
    Cui G (2009) The methods and mechanism for reducing viscosity of heavy oil by emulsifying. China Unversity of Petroleum (East China)Google Scholar
  3. 3.
    Wu X, Wu Y, Yang S et al (2016) Synergistic effect of pH-responsive wormlike micelles based on a simple amphiphile. Soft Matter 12(20):4549–4556CrossRefGoogle Scholar
  4. 4.
    Accelrys (2014) Material studio of 8.0 version, Accelrys Software Inc, San Diego, CAGoogle Scholar
  5. 5.
    Sun H (1998) COMPASS: an ab initio force field optimized for condensed-phase applications overview with details on alkane and benzene compounds. J Phys Chem B 102:7338–7364CrossRefGoogle Scholar
  6. 6.
    Peng Z, Ewig CS, Hwang M-J, Waldman M, Hagler AT (1997) Derivation of class II force fields, 4. Van der Waals parameters of alkali metal cations and halide anions. J Phys Chem A 101:7243CrossRefGoogle Scholar
  7. 7.
    Buuren van AR, Berendsen HJC (1994) Langmuir 10:1703–1713CrossRefGoogle Scholar
  8. 8.
    Berendsen HJC, Postma JPM, Gunsteren van WF et al (1984) J Chem Phys 81:3684–3690Google Scholar
  9. 9.
    Rosen JM, Kunjappu JT (2004) Surfactants and interfacial phenomena. Wiley, Hoboken, New Jersey, p 93Google Scholar
  10. 10.
    Zhao TT, Xu GY, Yuan SL et al (2010) Molecular dynamics study of alkyl benzene sulfonate at air/water interface: effect of inorganic salts. J Phys Chem B 114(15):5025–5033CrossRefGoogle Scholar
  11. 11.
    Jang SS, Lin ST, Maiti PK et al (2004) Molecular dynamics study of a surfactant-mediated decane-water interface: effect of molecular architecture of alkyl benzene sulfonate. J Phys Chem B 108(32):12130–12140CrossRefGoogle Scholar
  12. 12.
    Liu Z, Zhou Q (2000) Deduction of the regressive equation between density and pressure and between density and pressure and between density and temperature of saturated vapor. J Chongqing Jianzhu Univ 3:118–121Google Scholar
  13. 13.
    Rivera JL, Mccabe C, Cummings PT (2003) Molecular simulations of liquid–liquid interfacial properties: Water–n-alkane and water-methanol–n-alkane systems. Phys Rev E 67(1):011603CrossRefGoogle Scholar
  14. 14.
    Rivera JL, Predota M, Chialvo AA et al (2002) Vapor–liquid equilibrium simulations of the SCPDP model of water. Chem Phys Lett 357(3–4):189–194CrossRefGoogle Scholar

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© Springer Nature Singapore Pte Ltd. 2019

Authors and Affiliations

  1. 1.School of Petroleum EngineeringChina University of Petroleum (East China)QingdaoChina

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