Grosmont Dolomite Cores from Various Formation Depths after Bitumen Extraction: Dissolution in Brine and Interfacial Properties as a Function of Common Lattice Ion and pH

Dissolution and ζ potential of dolomitic particles obtained from six cores at various depths in the Grosmont carbonate formation were studied after the bitumen was extracted. Changes in specific conductivity and pH during mixing and after equilibration for 12 h were indicators of dissolution. Zeta potentials were measured as functions of pH and concentrations of common lattice cations Ca2+ and Mg2+ and the anion CO3 2– concentrations in an indifferent electrolyte NaCl background. The negative ζ potential decreased with increases in the added Ca2+ and Mg2+ concentrations and became more negative with incrementally added CO3 2– anion. The ζ potentials for all core solids became less negative when pH was reduced. The data were compared to responses of a model dolomite which displayed an isoelectric point around pH 5.8. None of the core solids showed an isoelectric point. They were not positively charged like the model dolomite when cation concentrations were increased in the suspending medium. The organic film left on the core solids surfaces after bitumen extraction was responsible for the nonideal electrokinetic behavior. There were minor differences in properties of the solid/liquid interfaces from core to core. There was no specific correlation with the depth of origination for the cores. The dissolution and electrical charge responses of the cores solids would suggest possible impact on emulsions that may form during bitumen extraction if water is used for extraction as in steam assisted gravity drainage processes. The properties of the residual core left after bitumen is removed would determine how the aquifer environments are affected.