METHOD FOR EXTRACTING CRUDE OIL FROM CRUDE OIL RESERVOIRS WITH A HIGH RESERVOIR TEMPERATURE

摘要

The present invention relates to a two-stage method for extracting crude oil from a crude oil reservoir that has a reservoir temperature at least 70°C and a salinity of between 20,000 and 350,000 ppm, in which an aqueous formulation comprising at least one glucan with a β-1,3-glycosidically-linked backbone chain and pendant groups with β-1,6-glycosidic bonds thereto, and with a weight-average molecular weight M_W of 1,5∙10⁶ to 25∙10⁶ g/mol, is injected into a crude oil reservoir through at least one injection borehole, and crude oil is removed from said reservoir through at least one production borehole. The aqueous formulation is produced in two stages, an aqueous concentrate of the glucan being produced first and the concentration then being diluted with water on-site to obtain the concentration for use selected such that the viscosity of the aqueous formulation is at least 3 mPa∙s, wherein said viscosity compared to the viscosity of oil is selected such that the viscosity of the aqueous formulation is ≤ the viscosity of oil, and the aqueous formulation is injected into an oil formation and crude oil is extracted through at least one production borehole.