Borate Crosslinked Fracturing Fluids
Borate crosslinked fluids are provided for use in oil and gas well fracturing operations. The fluids have relatively low loadings of galactomannan gums such as guar. The guar is present in an amount from about 10 to about 15 ppt. A borate crosslinking agent comprising ulexite is used to crosslink the guar and control the viscosity of the fluid.
1 . An aqueous well treatment fluid, said well treatment fluid comprising:
(a) a gelling agent selected from the group consisting of galactomannan gum and derivatives thereof in an amount from about 10 to about 15 ppt; and
(b) a borate crosslinking agent comprising ulexite.
2 . The fluid of claim 1 , wherein said gelling agent is present in an amount from about 10 to about 12 ppt.
3 . The fluid of claim 1 , wherein said gelling agent is guar.
4 . The fluid of claim 1 , wherein said crosslinking agent is present in an amount effective to provide said fluid with a viscosity of less than about 20 cP at high shear rates and at least about 25 cP at low shear rates.
5 . The fluid of claim 1 , wherein said crosslinking agent is present in an amount effective to provide said fluid with a viscosity of less than about 15 cP at high shear rates and at least about 25 cP at low shear rates.
6 . The fluid of claim 1 , wherein said crosslinking agent is present in an amount effective to provide said fluid with a viscosity of less than about 20 cP at high shear rates and at least about 50 cP at low shear rates.
7 . The fluid of claim 1 , wherein said crosslinking agent is present in an amount effective to provide said fluid with a viscosity of less than about 15 cP at high shear rates and at least about 50 cP at low shear rates.
8 . The fluid of claim 1 , wherein said crosslinking agent consists essentially of ulexite.
9 . The fluid of claim 7 , wherein ulexite is present in amounts sufficient to provide from about 0.1 to about 1 mole % crosslinking.
10 . The fluid of claim 7 , wherein ulexite is present in an amount from about 0.1 to about 0.2 g/100 ml.
11 . The fluid of claim 1 , said fluid recovers from a high shear rate viscosity of less than about 20 cP to a low shear rate viscosity of at least about 25 cP in less than about 10 seconds.
12 . The fluid of claim 1 , said fluid recovers from a high shear rate viscosity of less than about 15 cP to a low shear rate viscosity of at least about 25 cP in less than about 10 seconds.
13 . The fluid of claim 1 , said fluid recovers from a high shear rate viscosity of less than about 15 cP to a low shear rate viscosity of at least about 50 cP in less than about 3 minutes.
14 . The fluid of claim 1 , said fluid recovers from a high shear rate viscosity of less than about 20 cP to a low shear rate viscosity of at least about 100% greater than said high shear rate viscosity in less than about 10 seconds.
15 . The fluid of claim 1 , said fluid recovers from a high shear rate viscosity of less than about 15 cP to a low shear rate viscosity of at least about 100% greater than said high shear rate viscosity in less than about 10 seconds.
16 . The fluid of claim 1 , said fluid recovers from a high shear rate viscosity of less than about 15 cP to a low shear rate viscosity of at least about 150% greater than said high shear rate viscosity in less than about 90 seconds.
17 . The fluid of claim 1 , said fluid recovers from a high shear rate viscosity of less than about 15 cP to a low shear rate viscosity of at least about 200% greater than said high shear rate viscosity in less than about 2 minutes.
18 . The fluid of claim 1 , said fluid recovers from a high shear rate viscosity of less than about 15 cP to a low shear rate viscosity of at least about 300% greater than said high shear rate viscosity in less than about 3 minutes.
19 . The fluid of claim 1 , wherein said fluid does not comprise additional friction reducers.
20 . An aqueous well treatment fluid, said well treatment fluid comprising viscosity enhancing additives, said viscosity enhancing additives consisting essentially of:
(a) a gelling agent selected from the group consisting of galactomannan gum and derivatives thereof in an amount from about 10 to about 15 ppt; and
(b) a borate crosslinking agent comprising ulexite.
21 . The well treatment fluid of claim 20 , wherein said gelling agent is present in an amount from about 10 to about 12 ppt.
22 . The well treatment fluid of claim 20 , wherein said crosslinking agent consists essentially of ulexite.
23 . The well treatment fluid of claim 20 , wherein said fluid comprises a breaker.
24 . A method of fracturing a formation extending around a well, said method comprising:
(a) pumping the fluid of claim 1 into the formation at a rate and pressure sufficient to form fractures in the formation.
25 . A method of controlling the viscosity of an aqueous fluid injected into a well to induce fracturing of adjacent formations, said method consisting of:
(a) adding a gelling agent selected from the group consisting of galactomannan gum and derivatives thereof in an amount from about 10 to about 15 ppt and a borate crosslinking agent comprising ulexite to increase the viscosity of said aqueous fluid; and
(b) adding a breaker to decrease the viscosity of said aqueous fluid.
26 . The fluid of claim 1 , wherein said fluid comprises a proppant.
27 . The well treatment fluid of claim 20 , wherein said fluid comprises a proppant.