The analysis of the reasons for the decrease in the productivity of producing wells of Varadero oilfield was performed. It is established that the formation of deposits of asphaltenes in the bottom-hole formation zone and formation of highly viscous water-in-oil emulsions are the main reasons for the lower permeability of oil-saturated matrix of carbonate rocks. At temperature 65°C (reservoir temperature) Varadero oilfield oil has a viscosity more than 0,600 Pa·s. It is established that at temperature below 40 °C the oil is pseudoplasticity liquid and is well described by the rheological equation of Herschel – Bulkley. From the temperature dependence of the effective viscosity of the oil determined the optimal conditions for the application of thermal methods of enhanced recovery, with increasing temperature of the reservoir up to 80 -135 °C, the viscosity is reduced to 2-27 times.
The viscosity of water-oil emulsion at the reservoir temperature and water content more than 50% increases to 14 PA·s, the beginning of a sharp increase in viscosity is observed when the water content is more than 35%. Petroleum solvents and demulsifies introduced into an emulsion reduce its viscosity 20-50 times and are offered for treatment of producing wells in a continuous dispensing into the well and squeeze treatment into the reservoir. It is shown that the acid compositions on the basis of 12% HCl are compatible with oil and do not make a risk of formation of emulsions and precipitation of secondary collateralize formation.
The obtained information is used to develop optimal technologies of processing of bottom-hole zones of producing wells to increase the efficiency of heavy oil production.
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