  We performed mesoscale simulations in order to investigate the effects that
additives, such as surfactants and polymers, have in the oil displacement
process by water and brine injection. A Many-Body Dissipative Particle Dynamics
(MDPD) model was parameterized in order to reproduce physical properties
obtained either by experiments or Classical Molecular Dynamics (MD). The MDPD
model was then employed to simulate the displacement of n-dodecane by water and
brine, with surfactant concentrations ranging from 1 wt. % to 10 wt. % SDS and
polymer concentration of 0.5 wt. % HPAM. We observed that while the additives
may enter the capillary without clogging, specific combinations of surfactant
concentrations and injection rates may lead to poor oil displacement. This
result can be understood in terms of the balance between water-wall and
(surface-mediated) water-oil interactions. As a consequence, our results show
an effective reversal of the wettability character, from water-wet to oil-wet,
as a function of the interface speed. We conclude by summarizing the
implications such results have on the fluid-fluid displacements involving
additives.
