VISCOELASTIC COMPOSITION WITH IMPROVED VISCOSITY Russian patent published in 2013 - IPC E21B43/22 C09K8/584 

FIELD: oil and gas industry.

SUBSTANCE: invention refers to method of oil production from underground formation at maintaining the pressure, according to which: a) provision is made for pumping using at least one pumping device in contact with underground oil-containing formation, the fluid containing the mixture of at least the following components: i) saline water medium, ii) mixture of 2 zwitter-ion thickening surface active substances or mixture of 2 populations of those SAS, which has bimodal nature of narrow distribution of R₁ groups, modified definitions, in weight content at the interval of 1 to 0.05 wt %, mainly 0.5 to 0.1%, and more preferably 0.4 to 0.15% so that the fluid can have surface tension at the boundary line of water and oil, which is measured at ambient temperature - 25°C, approximately 10 mN/m or less, and viscosity measured at the temperature of 80°C and at shear gradient of 10 s^-1, approximately 3 cP or higher, which meet the specified formulae; the fluid is extracted at least with one extraction device located in the place different from that where polymer was introduced; at that, the above fluid contains oil.

EFFECT: improvement of stability or thickening in saline water, at high temperature, at reduction of the content of thickening SAS.

21 cl, 1 ex, 2 tbl