Method of Stimulating Subterranean Formation Using Low pH Fluid Containing a Glycinate Salt
Hydraulic fracturing is conducted by use of a well treatment fluid which contains a guar gum derivative as viscosifying or gelling polymer, an organic zirconate complex of a zirconium metal and an alkanol amine as crosslinking agent and a salt of a hydroxylated glycine as crosslinking delaying agent. The fluid is characterized by a low pH, generally greater than or equal to 3.0 and less than or equal to 5.0.
1 . A method of fracturing a subterranean formation penetrated by a well comprising the steps of:
(a) forming an aqueous fluid having a pH greater than or equal to 3.0 and less than or equal to 5.0, the aqueous fluid comprising:
(i) a guar gum derivative selected from the group consisting of carboxyalkyl guars and hydroxyalkylated guars;
(ii) an organic zirconate complex of a zirconium metal and an alkanol amine; and
(iii) a salt of a hydroxylated glycine; and
(b) pumping the fluid of step (a) down the well under sufficient pressure to fracture the subterranean formation.
2 . The method of claim 1 , wherein crosslinking of the aqueous fluid is delayed or inhibited until the aqueous fluid is placed at or near the fracturing site within the formation.
3 . The method of claim 1 wherein the guar gum derivative is a hydroxyalkylated guar.
4 . The method of claim 1 , wherein the guar gum derivative is selected from the group consisting of carboxymethyl hydroxypropyl guar, hydroxypropyl guar and carboxymethyl guar.
5 . The method of claim 1 , wherein the organic zirconate complex is an amine zirconium complex.
6 . The method of claim 1 , wherein the organic zirconate complex is in an alcohol solvent.
7 . The method of claim 6 , wherein the alcohol solvent is propanol.
8 . The method of claim 1 , wherein the salt of the hydroxylated glycine is a sodium, potassium, calcium, magnesium, zinc, zirconium, titanium, iron or ammonium salt.
9 . The method of claim 8 , wherein the salt of hydroxylated glycine is a sodium salt.
10 . The method of claim 9 , wherein the salt of hydroxylated glycine is a sodium salt of N,N-bis(2-hydroxyethyl)glycine.
11 . The method of claim 1 , wherein the aqueous fluid further comprises a foaming gas.
12 . The method of claim 11 , wherein the foaming gas is nitrogen or carbon dioxide.
13 . The method of claim 12 , wherein the foaming gas is carbon dioxide and further wherein the pH of the aqueous fracturing fluid is less than or equal to 3.7.
14 . The method of claim 1 , wherein the pH of the aqueous fluid is buffered between from about 4.0 to about 4.8.
15 . The method of clam 6 , wherein the organic zirconate complex is an amine zirconium complex in an alcohol solvent.
16 . A method of fracturing a subterranean formation penetrated by a well comprising the steps of:
(a) forming an aqueous fluid having a pH greater than or equal to 3.6 and less than or equal to 5.0, the aqueous fluid comprising:
(i) a guar gum derivative selected from the group consisting of hydroxyalkylated guars and carboxyalkyl guars;
(ii) an organic zirconate complex of a zirconium metal and an alkanol amine in an alcohol solvent; and
(iii) a salt of N,N-bis(2-hydroxyethyl)glycine; and
(b) pumping the fluid of step (a) down the well under sufficient pressure to fracture the subterranean formation.
17 . The method of claim 16 , wherein the salt of the N,N-bis(2-hydroxyethyl)glycine is present in the aqueous fluid in an amount sufficient to inhibit or delay crosslinking of the guar gum derivative and the organic zirconate complex until after the fluid has been pumped into the formation.
18 . The method of claim 16 , wherein the salt of N,N-bis(2-hydroxyethyl)glycine is a sodium, potassium, calcium, magnesium, zinc, zirconium, titanium, iron or ammonium salt.
19 . The method of claim 18 , wherein the salt of N,N-bis(2-hydroxyethyl)glycine hydroxylated glycine is a sodium salt.
20 . The method of claim 16 , wherein the aqueous fluid further comprises a foaming gas.
21 . The method of claim 16 , wherein the organic zirconate complex is an amine zirconium complex in an alcohol solvent.
22 . A method of fracturing a subterranean formation penetrated by a well comprising the steps of:
(a) forming an aqueous fluid having a pH greater than or equal to 3.6 and less than or equal to 5.0, the aqueous fluid comprising:
(i) a guar gum derivative selected from the group consisting of carboxymethyl guar, carboxymethylhydroxypropyl guar and hydroxypropyl guar;
(ii) an amine zirconium complex in an alcohol solvent; and
(iii) a sodium salt of N,N-bis(2-hydroxyethyl)glycine; and
(b) pumping the fluid of step (a) down the well under sufficient pressure to fracture the subterranean formation.
23 . The method of claim 22 , wherein the foaming gas is carbon dioxide and further wherein the pH of the aqueous fluid is less than or equal to 3.7.
24 . The method of claim 22 , wherein the aqueous fluid further comprises a buffer and the pH of the aqueous fluid is between from about 4.0 to about 4.8.