Choline-based crosslinker compositions for fracturing fluids
View Patent ↗Disclosed are compositions derived of mixtures of choline ion salts (typically choline chloride) in aqueous solution with suspended particulates of sparingly soluble borate minerals or with alkali or alkaline earth borate salts, boric acid and its ester derivatives and salts, or other aqueous soluble borate forms. These compositions are useful as cross-linkers for polysaccharides and other biopolymers and particularly as used in subterranean treatment fluids for completion and stimulation of oil and gas wells. Advantages of the compositions are the combination into a single package of the properties of clay stabilizing actives (choline ion) and crosslinking actives (borates, etc.), in relatively high concentrations, and these compositions are easy to handle, being stable and pumpable at low temperatures, and with attractive environmental profiles. Also disclosed are the analogous choline solutions mixed with metallic cross-linking ions know in the art such as Zr + , Ti 4+ , Al 3+ , & Fe 3+ .
1. A composition for crosslinking polymers in aqueous solution comprising from 5 wt. % to 60 wt. % of a crosslinking agent and from 5 wt. % to 95 wt. % of a base solution of aqueous choline salt, based on the total weight of the composition, wherein the crosslinking agent is in a stable solution or in a stable suspension and the particle size of the crosslinking agent is from about 20 mesh to about 400 mesh.
2. The composition of claim 1 , wherein the base solution is aqueous choline chloride.
3. The composition of claim 1 , further comprising an alcoholic or polyol co-solvent.
4. The composition of claim 1 , wherein the base solution suspends the crosslinking agent.
5. The composition of claim 1 , wherein the concentration of the aqueous choline salt is from 30 wt % to 70 wt % of the composition.
6. The composition of claim 3 , wherein the concentration of the co-solvent is from 1 wt % to 50 wt % of the composition.
7. The composition to claim 6 , wherein the concentration of the co-solvent is from 1 wt % to 30 wt % of the composition.
8. The composition of claim 6 , wherein the concentration of the co-solvent is from 5 wt % to 15 wt % of the composition.
9. The composition of claim 1 , wherein the crosslinking agents are transition metal containing compounds, the transition metal selected from the group consisting of titanium (4+), zirconium (4+) chromium (3+) iron (3+)and aluminum (3+), and the transition metal containing compounds release transition metal ions when dissolved in an aqueous liquid.
10. The composition of claim 1 , wherein the crosslinking agent is a borate releasing compound.
11. The composition of claim 1 , wherein the crosslinking agent is a mixture of a sparingly soluble alkali/alkaline earth metal borate and a slightly soluble borate.
12. The composition of claim 10 , wherein the crosslinking agent is:
(a) a sparingly soluble borate mineral selected from the group consisting of ulexite, colemanite, probertite, and a mixture thereof; or
(b) a slightly soluble borate and/or borate oxide selected from the group consisting of boric acid, common borax, sodium tetraborate, another alkali or alkaline earth borate hydrate, and a mixture thereof;
(c) or a mixture of (a) and (b).
13. The composition of claim 1 , wherein the concentration of the crosslinking agent is from 15 wt % to 45 wt % of the composition.
14. The composition of claim 3 , wherein the co-solvent is methanol, ethanol, 1- or 2-propanol, ethylene glycol, propylene glycol, glycerol, an alkyloxyethanol ether, diethylene glycol, an alkyldiethyleglycol ether, or a mixture thereof.
15. The composition of claim 1 further comprising a biocide, a pH adjuster, an antioxidant, or a combination thereof.
16. The composition of claim 1 wherein the crosslinking agent is in a stable suspension.