Removal of asphaltene deposition in porous media using emulsified solvents-A visual study

Asphaltene deposition may cause profound formation damages in oil reservoirs. Solvents of various types can be used to remove asphaltene deposition though they are expensive and prone to safety hazards and detrimental environmental consequences. In this study, emulsified solvents (i.e. toluene/water emulsions) were investigated as an alternative approach for the removal of asphaltene deposition in porous media. Three different emulsions (90/10, 80/20, 70/30 vol percentages of water in oil emulsions) were prepared and injected at two injection rates of 0.1 and 1.0 cc/hr into a transparent heterogeneous micromodel containing deposited asphaltene to evaluate their ability to either dislodge or dissolve asphaltene deposition and also to compare their performance with the use of pure toluene in both microscopic and macroscopic scales. The results showed that all of the investigated emulsions were able to remove, to some extent, the deposited asphaltene despite having a lower volume fraction of toluene. Furthermore, emulsions swept the whole area of porous media, but toluene left more than half the area of micromodel un-swept. Emulsion 70/30 (w/o) was found to be the optimum solvent as it removed all of the deposited asphaltenes at lower injected pore volumes. It was also found that the deposited asphaltene was removed with injecting lower pore volume of solvents, which was due to higher toluene penetration into deposition as the emulsified solvent flowed slower in the micromodel.