METHOD OF RE-FRACTURING USING BORATED GALACTOMANNAN GUM Russian patent published in 2019 - IPC E21B43/26 C09K8/514 

FIELD: chemistry.

SUBSTANCE: invention relates to re-fracturing of a subterranean formation. Method of re-fracturing a subterranean formation penetrated by a well having a number of zones, includes: a) hydraulic fracturing of the productive zone inside the subterranean formation, b) isolating the productive zone subjected to hydraulic fracturing from the second zone in the well by pumping to the well non-hydrated borated galactomannan gum and a cross-linking agent, where before transition to the cross-linked state, the non-hydrated borated galactomannan gum contains borate ions, and forming a thickened temporary seal by reacting said gum and cross-linking agent, thereby isolating said production zone from the second zone, c) breaking down said thickened temporary seal by injecting into the well a viscosity reducing agent, and reducing the viscosity of the thickened temporary seal by means of said agent pumped into well under pressure which is insufficient for the creation or expansion of fractures in the subterranean formation, and d) re-fracturing of said isolated zone after decomposition of the thickened temporary seal by pumping into the well a fluid for hydraulic fracturing of the formation under pressure, sufficient for the creation or expansion of fractures in the isolated productive zone subjected to hydraulic fracturing. Method of hydraulic fracturing a subterranean formation includes: a) pumping to the well non-hydrated borated galactomannan gum and a cross-linking agent, b) sealing the productive zone subjected to hydraulic fracturing relative to the other zone in the well by means of gel for temporary isolation due to the reaction of said gum and cross-linking agent to form temporary isolation gel from the product of said reaction, c) pumping into the well a viscosity reducing agent, reducing the viscosity of the gel for temporary isolation, removing the seal of said productive zone relative to another zone and removing the gel for temporary isolation from the well, where said agent is pumped into the well under pressure which is insufficient for the creation or expansion of fractures in the subterranean formation, d) re-fracturing the unsealed productive zone, subjecting it to hydraulic fracturing by pumping into said zone a fluid for hydraulic fracturing of a formation under pressure sufficient for the creation or expansion of fractures, e) pumping said gum and cross-linking agent into the well and forming a gel for temporary isolation between the zone subjected to re-fracturing, and another zone by reacting said gum and cross-linking agent. Method for increasing productivity of oil-and-gas bearing formation penetrated by a well, having a number of productive zones, includes a) forming a gel for temporary isolation between a zone previously subjected to hydraulic fracturing and another zone by pumping said gum and delayed-action crosslinking agent and reaction thereof, b) pumping a viscosity reducing agent into the well, reducing the viscosity of the gel for temporary isolation and then removing it from the well, c) pumping into the well a fluid for hydraulic fracturing of the formation under pressure sufficient to create or expand the fracture in the subterranean formation, and re-fracturing the productive zone, d) injecting into well a well treatment fluid containing said gum and delayed-action crosslinking agent, and e) isolating said production zone by curing the well treatment fluid containing said gum and delayed-action crosslinking agent. Invention is developed in dependent items of the formula.

EFFECT: technical result is higher efficiency of re-fracturing treatment.

20 cl, 7 dwg, 2 tbl, 9 ex