Sulfates and Phosphates as Allosteric Effectors in Mannanohydrolase Enzyme Breakers
AssigneeBaker Hughes Incorporated
InventorsCharles David Armstrong, Hoang Le, Bharath Rajappa, Qi Qu
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Abstract
The allosteric effectors, sulfate and phosphate, can be used with mannanohydrolase enzymes to better control the break of gelled fracturing fluids in wellbore operations.
Claims26
In a method of fracturing a subterranean formation comprising introducing into the formation an aqueous fracturing fluid comprising:
- a. a hydratable polymer selected from the group consisting of guar, guar derivatives, cellulose derivatives, water soluble biopolymers, and combinations thereof;
- b. a crosslinking agent for crosslinking the hydratable polymer to form a polymer gel;
- c. an enzyme breaker comprising an 1,4-β-mannanase;
- the improvement being adding a sulfate or a phosphate to the aqueous fracturing fluid.
The method of claim 11, wherein the intrinsic viscosity of the hydratable polymer in the aqueous fracturing fluid is greater than about 16 dl/g.
An aqueous fracturing fluid comprising:
- a. a hydratable polymer selected from the group consisting of guar, guar derivatives, cellulose derivatives, water soluble biopolymers, and combinations thereof;
- b. a crosslinking agent for crosslinking the hydratable polymer to form a polymer gel;
- c. an enzyme breaker comprising at least one of the following:
- i. a mannanohydrolase enzyme that is coded by the nucleotide sequence shown in FIG. 1A, or a nucleotide sequence which is at least 60% homologous with the sequence of FIG. 1A, or when translated, has the amino acid sequence which is at least 60% homologous to the amino acid sequence of FIG. 1B;
- ii. an alkaline mannanohydrolase enzyme that is coded by the nucleotide sequence shown in FIG. 2, or a nucleotide sequence which is at least 60% homologous with the sequence of FIG. 2;
- or
- iii. a mannanohydrolase enzyme that is a member of the glycosyl hydrolase family 5 and is coded for by a gene sequence as depicted in FIG. 2;
- and
- d. a sulfate or a phosphate.
A method of fracturing a subterranean formation comprising introducing into the formation an aqueous fracturing fluid comprising:
- a) a hydratable polymer selected from the group consisting of guar, guar derivatives, cellulose derivatives, water soluble biopolymers, and combinations thereof;
- b) a crosslinking agent for crosslinking the hydratable polymer to form a polymer gel;
- c) an enzyme breaker comprising at least one of the following:
- (i) a mannanohydrolase enzyme that is coded by the nucleotide sequence shown in FIG. 1A, or a nucleotide sequence which is at least 60% homologous with the sequence of FIG. 1A, or when translated, has the amino acid sequence which is at least 60% homologous to the amino acid sequence of FIG. 1B;
- (ii) a mannanohydrolase enzyme that is coded by the nucleotide sequence shown in FIG. 2, or a nucleotide sequence which is at least 60% homologous with the sequence of FIG. 2;
- or
- (iii) an mannanohydrolase enzyme that is a member of the glycosyl hydrolase family 5 and is coded for by a gene sequence as depicted in FIG. 2;
- and
- d) a sulfate or a phosphate in about a 1:1 stoichiometric ratio with the enzyme breaker.
Dependencies are inferred from the claim text.