Polysaccharide treatment fluid and method of treating a subterranean formation
A treatment fluid for treating a subterranean formation penetrated by a wellbore is formed from an aqueous medium, a diutan heteropolysaccharide having a tetrasaccharide repeating unit in the polymer backbone and a peroxide breaker. A method of treating a subterranean formation penetrated by a wellbore may be carried out by introducing the treatment fluid into the formation through the wellbore. Breaking aids or catalysts may also be used with the treatment fluid.
1. A treatment fluid for treating a subterranean formation penetrated by a wellbore comprising:
an aqueous medium;
a diutan heteropolysaccharide having a tetrasaccharide repeating unit in the polymer backbone as represented by the formula:
wherein at least three different saccharides are present in the repeating unit, such saccharides including D-glucose, D-glucuronic acid, and either L-rhamnose or L-mannose; M + is an ionic species; R 1 , R 2 , R 3 , R 4 , R 5 , R 6 , R 7 , R 8 , R 9 , and R 10 are selected from the group consisting of hydrogen, methyl, acetyl, glyceryl, or a saccharide group containing one to three saccharides units; R 11 is a methyl or methylol group; and the weight average molecular weight (Mw) for the heteropolysaccharide is from about 10 5 to about 10 7 ;
a diutan reactive peroxide breaker;
a breaking aid or catalyst; and,
an iron contamination control agent, wherein the breaking agent or catalyst is at least one of iron (II) sulfate or a hydrate thereof, iron (II) chloride, iron (II) gluconate, iron powder with a pH-adjusting agent, or a combination of these.
2. The treatment fluid of claim 1 , wherein the iron contamination control agent is selected from the group consisting of N-(2-hydroxyethyl)ethylenediamine-N,N′,N ′-triacetic acid (HEDTA) and salts thereof, ethylenediaminetetraacetic acid (EDTA) and salts thereof, nitrilotriacetic acid and salts thereof, ethanoldiglycine and salts thereof, diethylene triamine pentaacetic acid (DTPA) and salts thereof, ethylene glycol tetraacetic acid (EGTA) and salts thereof, phosphonic acids and salts thereof, sodium erythorbate, hydroxymethylsulfinates, D-isoascorbic acid (or erythorbic acid) and salts thereof, ascorbic acid and salts thereof, L-ascorbic acid and salts thereof, D-erythroascorbic acid and salts thereof, thioglycolic acid and salts thereof, other thiols, and any combination thereof.
3. The treatment fluid of claim 1 , further comprising a surfactant and an electrolyte.
4. The treatment fluid of claim 1 , further comprising a gas component.
5. The treatment fluid of claim 1 , wherein the peroxide breaker is a stabilized peroxide breaker.
6. The treatment fluid of claim 1 , wherein the peroxide breaker is selected from a group consisting of hydrogen peroxide, superoxides, metal peroxides, organic peroxides, urea peroxide, percarbonates, persulfates, perborates and hydrates thereof, surfactant-stabilized peroxides, encapsulated peroxides or combinations of these.
7. The treatment fluid of claim 1 , wherein the peroxide breaker is selected from a group consisting of urea peroxide, sodium percarbonate, potassium percarbonate, ammonium percarbonate, sodium persulfate, potassium persulfate, ammonium persulfate, sodium perborate, hydrogen peroxide, a surfactant-stabilized peroxide, an encapsulated peroxide or combinations of these.
8. The treatment fluid of claim 1 , wherein the peroxide breaker is present in the fluid in an amount of from about 0.001% to 20% by weight of the fluid.
9. The treatment fluid of claim 1 , wherein the diutan heteropolysaccharide is present in the fluid in an amount of from about 0.01% to about 4% by weight of the treatment fluid.
10. The treatment fluid of claim 1 provided a crosslinker is not incorporated to effectively increase viscosity of the treatment fluid.