Well-known technology of solvent-based recovery of heavy (extra-viscous) oils and bitumens has a number of indisputable advantages. They include the possibility of development of thin oil reservoirs, reduced or zero water consumption, significant decrease in the capital and operating expenditures, and reduction of the overall power consumption up to 85%. The results of the current pilot projects show that this technology is competitive even in conditions of low oil prices. Physical simulation of the oil displacement process in conditions corresponding to the Ashalchinskoye field allows evaluating the applicability of composite solvents based on light aliphatic and aromatic hydrocarbons. It was established that application of the composite solvent based on the light saturate hydrocarbons only leads to deposition of the oil residues enriched with asphaltenes (up to 50-60%) in the pore space. With the increase of proportion of aromatic hydrocarbon (toluene) in the composite solvent, precipitation of asphaltenes is decreased proportionally. Experimental simulation revealed the optimal concentration of aromatic hydrocarbon in the composite solvent based on pentane-hexane fraction for effective displacement of the extra-viscous oil. The velocity of the oil displacement and the volume of recoverable oil are both increased when the amount of asphaltenes deposited in the pore space is decreased. Various synthetic and natural amphiphilic substances behaving as inhibitors of asphaltene deposition process can be used in the composite solvent instead of toluene and other aromatic hydrocarbons.
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