Method and compositions for fracturing subterranean formations

Claim 2

An aqueous gel comprising: an aqueous fluid comprising a water-alcohol solution having from about 0 to 80 percent alcohol by volume; a gelling agent comprising a solvatable polysaccharide having a molecular weight in excess of about 100,000 present in an amount sufficient to gel said aqueous fluid; and a retarded crosslinking composition, present in an amount sufficient to crosslink at least a portion of said gelling agent, comprising an organotitanate chelate which is soluble in said aqueous fluid, a polyhydroxyl-containing compound comprising at least one member selected from the group consisting of glycerol, erythritol, threitol, ribitol, arabinitol, xylitol, allitol, altritol, sorbitol, mannitol, dulcitol, iditol, and perseitol and an aqueous fluid, said retarded crosslinking composition having been aged for a period of at least about one hour prior to admixing with said solvatable polysaccharide and said constituents of said retarded crosslinking composition being present in a volumetric ratio, respectively, in the range of from about 1:0.05:0.05 to about 1:10:10.

Claim 3

The aqueous gel of claim 1 wherein said solvatable polysaccharide is selected from the group consisting of guar gum, locust bean gum, karaya gum, sodium carboxymethylguar, hydroxyethylguar, sodium carboxymethylhydroxyethylguar, hydroxypropylguar, and sodium carboxymethylhydroxpropylguar.

Claim 4

The aqueous gel of claim 1 wherein said crosslinking compound comprises at least one member selected from the group consisting of titanium-triethanolamine chelate, titanium-ammonium lactate chelate and titanium-acetylacetonate chelate.

Claim 5

The aqueous gel of claim 1 wherein said crosslinking compound, polyhydroxyl-containing compound and aqueous fluid of said retarded crosslinking composition are present in a volumetric ratio, respectively, in the range of from about 1:0.1:0.1 to about 1:4:4.

Claim 6

A process for fracturing a subterranean formation which comprises: introducing into said formation an aqueous gel at a flow rate and pressure sufficient to produce a fracture in said formation, said aqueous gel being comprised of an aqueous fluid, a gelling agent comprising a solvatable polysaccharide having a molecular weight of least about 100,000 a retarded crosslinking composition, present in an amount sufficient to crosslink at least a portion of said gelling agent, comprising organotitanate chelates having titanium in the +4 oxidation state, a polyhydroxyl-containing compound comprising at least one member selected from the group consisting of glycerol, erythritol, threitol, ribitol, arabinitol, xylitol, allitol, altritol, sorbitol, mannitol, dulcitol, iditol, and perseitol and an aqueous fluid which are present in said retarded crosslinking composition in a volumetric ratio, respectively, in the range of from about 1.0:0.05:0.05 to about 1:10:10, said retarded crosslinking composition having been aged for at least about one hour prior to admixing to form said aqueous gel.

Claim 7

A process for fracturing a subterranean formation which comprises: introducing into said formation an aqueous gel at a flow rate and pressure sufficient to produce a fracture in said formation, said aqueous gel being comprised of an aqueous fluid, a gelling agent comprising a solvatable polysaccharide having a molecular weight of least about 100,000 a retarded crosslinking composition, present in an amount sufficient to crosslink at least a portion of said gelling agent, comprising organotitanate chelates having titanium in the +4 oxidation state, a polyhydroxyl-containing compound comprising at least one member selected from the group consisting of glycerol, erythritol, threitol, ribitol, arabinitol, xylitol, allitol, altritol, sorbitol, mannitol, dulcitol, iditol, and perseitol and an aqueous fluid which are present in said retarded crosslinking composition in a volumetric ratio, respectively, in the range of from about 1.0:0.05:0.05 to about 1:10:10, said retarded crosslinking composition having been aged for at least about one hour prior to admixing to form said aqueous gel.

Claim 8

The process of claim 5 wherein said solvatable polysaccharide is selected from the group consisting of galactomannans, glucomannans, and derivatives thereof.

Claim 9

The process of claim 5 wherein said crosslinking compound comprises at least one member selected from the group consisting of titanium-triethanolamine chelate, titanium-ammonium lactate chelate and titanium-acetylacetonate chelate.

Claim 10

The process of claim 5 wherein said polyhydroxyl-containing compound comprises at least one member selected from the group consisting of glycerol, sorbitol, perseitol and mixtures thereof.

Claim 11

The process of claim 5 wherein said gelling agent is present in said aqueous fluid in a concentration in the range of from about 0.2 to about 1.25 percent by weight of said aqueous fluid.

Claim 12

The proces of claim 5 wherein said aqueous fluid comprises a water-alcohol solution having in a range of from about 0 to about 80 percent alcohol by volume of solution.

Claim 13

The process of claim 10 wherein said alcohol is selected from alkanols having from 1 to 5 carbon atoms.

Claim 14

The process of claim 5 wherein said retarded crosslinking composition is present in the range of from about 0.1 gallon to about 0.5 gallon per 10 pounds of gelling agent.

Claim 15

The process of claim 5 wherein said solvatable polysaccharide is selected from the group consisting of guar gum, locust bean gum, karaya gum, sodium carboxymethylguar, hydroxyethylguar, sodium carboxymethylhydroxyethylguar, hydroxypropylguar, and sodium carboxymethylhydroxypropylguar.

Claim 16

The process of claim 5 wherein said crosslinking compound, polyhydroxyl-containing compound and aqueous fluid of said retarded crosslinking composition are present in a volumetric ratio, respectively, in the range of from about 1:0.1:0.1 to about 1:4:4.

Claim 17

A process for hydraulically fracturing a subterranean formation penetrated by a well bore which comprises: preparing a base gel by mixing an aqueous fluid comprising a water-alcohol solution having in a range of from about 0 to about 80 percent alcohol by volume of solution with a gelling agent selected from solvatable polysaccharides having a molecular weight of at least about 100,000; admixing a retarded crosslinking composition with said gelling agent in an amount sufficient to crosslink at least a portion of said gelling agent, said retarded crosslinking composition comprising: (i) a crosslinking compound soluble in said aqueous fluid comprising an organotitanate chelate having titanium in the +4 oxidation state, (ii) a polyhydroxyl-containing compound comprising at least one member selected from the group consisting of glycerol, erythritol, threitol, ribitol, arabinitol, xylitol, allitol, altritol, sorbitol, mannitol, dulcitol, iditol and perseitol and (iii) an aqueous fluid present in said retarded crosslinking composition in a ratio, respectively, in the range of from about 1:0.05:0.05 to about 1:10:10 with said base gel, said retarded crosslinking composition having been aged for a period of at least about one hour, said retarded crosslinking composition being capable of delaying the reaction rate of said crosslinking compound with said gelling agent of said base gel; introducing said base gel containing said retarded crosslinking composition into said well bore; permitting said base gel and said crosslinking compound to react after a controllable period of time to form a crosslinked aqueous gel, at least a portion of the delay in the rate of said reaction resulting from the presence of said polyhydroxyl-containing compound and aqueous fluid in said retarded crosslinking composition; and introducing said crosslinked aqueous gel into said formation from said well bore at a flow rate and pressure sufficient to produce a fracture in said formation.

Claim 18

A process for hydraulically fracturing a subterranean formation penetrated by a well bore which comprises: preparing a base gel by mixing an aqueous fluid comprising a water-alcohol solution having in a range of from about 0 to about 80 percent alcohol by volume of solution with a gelling agent selected from solvatable polysaccharides having a molecular weight of at least about 100,000; admixing a retarded crosslinking composition with said gelling agent in an amount sufficient to crosslink at least a portion of said gelling agent, said retarded crosslinking composition comprising: (i) a crosslinking compound soluble in said aqueous fluid comprising an organotitanate chelate having titanium in the +4 oxidation state, (ii) a polyhydroxyl-containing compound comprising at least one member selected from the group consisting of glycerol, erythritol, threitol, ribitol, arabinitol, xylitol, allitol, altritol, sorbitol, mannitol, dulcitol, iditol and perseitol and (iii) an aqueous fluid present in said retarded crosslinking composition in a ratio, respectively, in the range of from about 1:0.05:0.05 to about 1:10:10 with said base gel, said retarded crosslinking composition having been aged for a period of at least about one hour, said retarded crosslinking composition being capable of delaying the reaction rate of said crosslinking compound with said gelling agent of said base gel; introducing said base gel containing said retarded crosslinking composition into said well bore; permitting said base gel and said crosslinking compound to react after a controllable period of time to form a crosslinked aqueous gel, at least a portion of the delay in the rate of said reaction resulting from the presence of said polyhydroxyl-containing compound and aqueous fluid in said retarded crosslinking composition; and introducing said crosslinked aqueous gel into said formation from said well bore at a flow rate and pressure sufficient to produce a fracture in said formation.

Claim 21

The process of claim 15 wherein said solvatable polysaccharide is selected from the group consisting of guar gum, locust bean gum, karaya gum, sodium carboxymethylguar, hydroxyethylguar, sodium carboxymethylhydroxyethylguar, hydroxypropylguar, and sodium carboxymethylhydroxypropylguar.

Claim 22

The process of claim 15 wherein said crosslinking compound comprises at least one member selected from the group consisting of titanium-triethanolamine chelate, titanium-ammonium lactate chelate and titanium-acetylacetonate chelate.

Claim 23

The process of claim 15 wherein said polyhydroxyl-containing compound comprises at least one member selected from the group consisting of glycerol, sorbitol, perseitol and mixtures thereof.

Claim 24

The process of claim 15 wherein said gelling agent is present in said aqueous fluid in a concentration in the range of from about 0.2 to about 1.25 percent by weight of said aqueous fluid.

Claim 25

The process of claim 15 wherein said retarded crosslinking composition is present in the range of from about 0.1 gallon to about 0.5 gallon per 10 pounds of gelling agent.