Non-conventional techniques to characterize complex SAGD emulsions and dilution effects on emulsion stabilization

A detailed characterization of a produced emulsion, obtained from Steam Assisted Gravity Drainage (SAGD) operations, as well as synthetic emulsions, prepared after diluting the oil with three different solvents, was carried out. Reference samples were also used for comparison purposes, in which the oil phase was solely composed of diluent. Non-conventional techniques such as Differential Scanning Calorimetry (DSC) and Multiple Light Scattering with near infrared radiation were employed for the studies. DSC was used to determine the type of emulsion and to quantify the amount of free and emulsified water for either synthetic or produced emulsions. The stability of the emulsions was monitored by using multiple light scattering of near infrared radiation and it was correlated with the compositional differences of the diluents (paraffinic vs aromatic nature and surface active compounds) and their potential effects on asphaltene precipitation. A comparison of the results with droplet size and zeta potential values indicated that stability in this type of emulsions results from a balance of the steric and electrostatic mechanisms, the former being the dominating force. Model oils were also prepared by diluting extracted asphaltenes with toluene and mixtures of toluene and heptane. It was demonstrated that asphaltene aggregates can be present even at concentrations as low as 0.005 wt% and they play a key role on SAGD emulsion stabilization.