HYDROCARBON RECOVERY METHOD Russian patent published in 2015 - IPC E21B43/22 

FIELD: oil and gas industry.

SUBSTANCE: invention is related to hydrocarbons from underground formation. The method of raw oil recovery from a reservoir, including at least one oil-bearing porous underground subsurface with connate water and oil in cavities of the rock pores having API density less than 25° and containing suspended undissolved solids (SUS), lies in injection of input water to the rock, wherein the input water contains SUS and total content of dissolved solids (TCDS) in it is equal to 30000 ppm or less, the ratio of total content of multivalent cations (MC) in the input water to total MC content in connate water is less than 0.9, and receipt of water-in-oil emulsion inside hydrocarbon-bearing rock; total SUS content in the input water and raw oil is sufficient for SUS content in emulsion to be at least 0.05% per emulsion mass and SUS in the input water is equal to at lest 0.05 kg/m³ and average size of particles is 10 mcm or less, raw oil in pores contains at least 0.05% of SUS with the same average size, total acid number (TAN) of oil is at least 0.5 mg of KOH/g, asphaltene content in it is at least 1-20 wt % and resin content is 5-30 wt %. The invention also suggests increase in recovery degree of raw oil from the above reservoir with connate water and oil in cavities of the rock pores having API density less than 25° and containing SUS with average diameter less than 2 mcm in quantity equal to at least 0.01 wt %, with TAN of at least 0.5mg of KOH/g, asphaltene content of at least 1 wt % and resin content of 5-30 wt %, and the input water is injected to the rock in order to receive water-in-oil emulsion in it, where this water is collected by determination of MC content in connate water, extraction of the input water containing dissolved solids (DS) in quantity less than 30000 ppm, the total MC content is such that the ratio of total MC content in the input water to total MC content in connate water is less than 0.9 and contains at least 0.05 wt % of SUS with average diameter less than 2 mcm in the above water. Invention has been developed in dependent claims.

EFFECT: improving washing efficiency and reducing quantity of residual oil in the rock.

9 cl, 3 ex, 4 dwg, 4 tbl