Viscosity Reduction and Anticipation of the Phase Inversion Point of Water-in-Oil (W/O) Emulsions Flowing in a Pipeline in the Presence of Demulsifier - Part I: Study of the Emulsions Behavior and Phenomenaviscosity Reduction and Anticipation of the Phase Inversion Point of Water-in-Oil (W/O) Emulsions Flowing in a Pipeline in the Presence of Demulsifier - Part Ii: Modeling Apparent Viscosity Reduction