Oil-based slurries and methods for making thereof
Disclosed herein is a copolymer concentrate in a bio-solvent that can be further diluted into a slurry composition. The bio-solvent facilitates the formation of a viscosified base fluid with the mixing being carried out in a short period of time and at ambient, providing a free flowing, pumpable, and dispersible slurry. The slurry is characterized as having excellent stability, maintaining suspension over a wide range of temperatures. In embodiments, the bio-solvent is selected from terpene and terpene-derivative-containing solvents, fatty acid alkyl esters, and mixtures thereof. The bio-solvent can be first mixed with a styrenic diblock copolymer to form a concentrate prior mixing with a hydrocarbon solvent, forming a viscosified base fluid for subsequent mixing with a water-soluble polymer to form the slurry. The bio-solvent can also be used to dilute the hydrocarbon solvent, prior to mixing with the styrenic diblock copolymer to form the viscosified base fluid.
1. A method for making a slurry for subsequent dilution, forming a fluid for injection into a subterranean formation, the method comprising:
a) dissolving a styrenic diblock copolymer in amount of equal to or greater than 15 wt. % in a bio-solvent, forming a pourable concentrate having a viscosity of less than 10,000 cP at a shear rate of 600 s −1 ;
b) dissolving the pourable concentrate in a sufficient amount of a hydrocarbon solvent forming a mixture having a concentration of 1 to 3 wt. % of the styrenic diblock copolymer; and
c) adding a water-soluble polymer into the mixture forming the slurry, for a concentration of the water-soluble polymer of 40-70 wt. % based on the total wt. % of the slurry;
wherein the styrenic diblock copolymer has a formula A-B, wherein A is a monoalkenyl arene and B is a conjugated diene block;
wherein the bio-solvent is selected from the group consisting of terpene and terpene-derivative-containing solvents, fatty acid alkyl esters, and mixtures thereof;
wherein the hydrocarbon solvent is selected from the group consisting of mineral oils, kerosene, jet-fuel, white oils, diesel oils, olefins, organic esters, synthetic fluids, and mixtures thereof;
wherein the water-soluble polymer is selected from the group consisting of water-based polysaccharides, polyethylene oxide, acrylamide polymers, and mixtures thereof; and
wherein the styrenic diblock copolymer maintains the water-soluble polymer in suspension in the slurry with less than 3 wt. % free hydrocarbon solvent separation after at least 1 day standing.
2. The method of claim 1 , wherein the pourable concentrate composition further comprises additives in an amount of at >0.5 wt. %, based on the total weight of the pourable concentrate composition.
3. The method of claim 1 , wherein the bio-solvent is present in an amount of >60 wt. %, based on the total weight of the pourable concentrate composition.
4. The method of claim 1 , wherein the bio-solvent is present in an amount of >5 wt. %, based on the total weight of the bio-solvent and the hydrocarbon solvent.
5. The method of claim 1 , wherein the hydrocarbon solvent and the bio-solvent are present at a weight ratio of 5:95 to 15:85.
6. The method of claim 1 , wherein the styrenic diblock copolymer is a hydrogenated styrene-(ethylene/propylene) styrene (SEPS) block copolymer.
7. The method of claim 1 , wherein the styrenic diblock copolymer has a peak molecular weight of 200-250 kg/mole and a polystyrene (PSC) content of 30-50%.
8. The method of claim 1 , wherein the styrenic diblock copolymer is coated with a dusting agent in an amount of 0.02 to 2 wt. %, based on the total weight of the styrenic diblock copolymer;
wherein the dusting agents is selected from the group consisting of fumed silica, talc, calcium carbonate, and mixtures thereof.
9. The method of claim 1 , wherein the slurry has a Turbiscan Stability Index of ≤2.0.
10. A slurry prepared by the method of claim 1 .
11. The slurry of claim 10 , wherein the slurry has a viscosity of 500-2200 cp.