Asphaltene deposition in miscible gas flooding of oil reservoirs

Gas and water flooding of oil reservoirs are the most commonly adopted operations to enhance oil recovery. The interaction between the injection fluid and reservoir oil may, however, precipitate asphaltic particles of oil and potentially causes serious operating problems and loss of recovery. An experimental investigation of asphaltene deposition in oil reservoirs by miscible gas flooding has been conducted. Flow visualisation experiments were performed in high pressure glass micromodels. The micromodel was also deployed in series with a compatible glass bead pack. The observations and the measurements made are reported and discussed. Miscible displacement of oil with propane did not result in significant precipitation of asphaltenes within the pores. However, bulk mixing of propane and oil promoted asphaltene flocculation pore plugging and permeability impairment which could result in a severe loss of fluid production. The adsorption of asphaltic material on reservoir rock surfaces can also alter the rock permeability and fluid distribution in pores and hence affect ultimate oil recovery.