title: Coarse-Grained Simulations of Polymer-Grafted Nanoparticles: Structural Stability and Interfacial Behavior.
abstract: In the tertiary oil recovery method known as "polymer flooding", the viscosity of the injected water is increased by dissolving partially hydrolyzed polyacrylamide so as to lower the mobility ratio and raise the vertical and areal sweep efficiencies. However, its drawbacks include the degradation of the polymer in the reservoir due to (1) shear while passing through chokes, perforations, and pore throats, (2) morphological changes induced by divalent ions, and (3) complete hydrolysis of the polymer at high temperatures. These factors adversely affect the viscosity of the polymer flood. Past experimental research showed that polymer-grafted nanoparticles (PNPs) could achieve the same viscosity enhancement at lower quantities than traditional linear polymers. The PNPs have the putative advantage of greater stability when confronted with the aforementioned reservoir conditions. In this work, we use dissipative particle dynamics (DPD) to simulate the oil-PNP-water system at the mesoscale and estimate its sensitivity to brine in ways that could serve as guidelines to experiments. We study the effect of salinity on the structure of linear and branched polyelectrolytes before extending the DPD model to PNPs at the oil-water interface. To this end, we parameterize the interactions of the polymer with the oil and water phases, and broadly map out solvent conditions that change the graft's morphology and affect the interfacial behavior of the grafted particle. We find that the equilibrium location of the grafted nanoparticle in an oil-brine system depends on its grafting density and the salinity.
authors: Shell India Markets Private Limited , Bangalore 560048, India.
authors: Nitish
authors: N
authors: Nair
authors: Massachusetts Institute of Technology , Cambridge, Massachusetts 02139, United States.
authors: Michelle
authors: M
authors: Park
authors: Culgi B.V. , P.O. Box 252, Leiden 2300 AG, The Netherlands.
authors: Jan-Willem
authors: JW
authors: Handgraaf
authors: Shell International Exploration and Production , Westhollow, Houston, Texas 77082-3101, United States.
authors: Flavia M
authors: FM
authors: Cassiola