METHODS AND FLUIDS FOR WELL TREATMENT Russian patent published in 2019 - IPC E21B43/267 C09K8/68 

FIELD: technological processes.

SUBSTANCE: invention relates to methods and fluids for well treatment with increasing oil recovery. Method of well treatment by hydraulic fracturing of formation includes formation of fluid for treatment of well at mixing of ingredients, including water fluid, thickener, stapler and a rheological modifier containing a dialdehyde, where fluid for well treatment does not contain additive, slowing down stitching dialdehyde, stitching of thickener in aqueous fluid using stapler, where dialdehyde does not require slowing down stitching and stitching increases viscosity of fluid for treatment of well to first viscosity, well treatment with fluid for well treatment, characterized by first viscosity, chemical conversion of dialdehyde after stitching with formation of diacid, wherein dialdehyde is subjected to insignificant chemical conversion before stitching, and after treatment of well, reduced viscosity of cross-linked fluid for treatment of well to second viscosity, less than first viscosity, under action of diacid. Method of well treatment by hydraulic fracturing of formation includes formation of fluid for treatment of well at mixing of ingredients, including water fluid, thickener, stapler, containing zirconium, and rheological modifier containing glyoxal, stitching of thickener in aqueous fluid using stapler, where dialdehyde requires no deceleration stitching and stitching increases viscosity of fluid for treatment of well to first viscosity, treatment of well with fluid for treatment of well, characterized by first viscosity, chemical conversion of glyoxal after stitching with formation of oxalic acid, wherein glyoxal is subjected to insignificant chemical conversion before stitching, after treatment of well, disruption of transverse bonds formed by zirconium under action of oxalic acid and reduced viscosity of cross-linked fluid for treatment of well to second viscosity, lower than first viscosity, under action of oxalic acid. Method of treating a well by hydraulic fracturing of a formation comprises forming a well treatment fluid while mixing ingredients including produced water, a thickener, stapler, containing metal cation, and rheological modifier containing dialdehyde, and zirconium compound, wherein the produced water contains only more than 1000 ppm of the dissolved solid substances and the well treatment fluid does not contain an additive which slows down stitching dialdehyde, dissolving at least part of zirconium compound in fluid for well treatment, stabilization of fluid pH for well treatment using zirconium compound, stitching of thickener in aqueous fluid using stapler and dissolved zirconium from zirconium compound, where dialdehyde requires no deceleration stitching and stitching increases viscosity of fluid for treatment of well compared to fluid for treatment of well, which does not contain zirconium compound, well treatment by fluid for well treatment, characterized by higher viscosity, chemical conversion of dialdehyde after stitching with formation of diacid, low pH and formation of chelate complexes of metal cation and dissolved zirconium with diacid, wherein the fluid cross-links for the well treatment are broken, and using the diacid the viscosity is reduced cross-linked fluid for well treatment in comparison with cross-linked fluid for well treatment, which does not contain rheological modifier. Invention is developed in dependent items of the formula.

EFFECT: higher efficiency of treatment.

19 cl, 10 dwg, 4 tbl, 10 ex