Method for making nano- and micro-particles for use as a proppant and fluid-loss-control additive
Nano- and micro-particles (NMP) can be formed from an oil/water emulsion. The emulsion is made by mixing a liquid solvent, at least one surfactant, a particle-forming compound, and at least curing agent. If desired, pH control agents and viscosity enhancers can be added to the liquid solvent. The particle-forming compound and the curing agents are mixed together and form the oil phase in the emulsion and after curing, the particles are formed. The nano- and micro-particles can be used as proppant to enhance the conductivity of nano- and microfractures and fluid-loss-control additive for hydraulic fracturing operations.
1. A method for producing a mixture of nano- and micro-particles for use as a proppant and fluid-loss-control additive, comprising:
mixing a liquid solvent, at least one surfactant, a particle-forming compound, and at least one curing agent to form an emulsion, and at least one pH control agent that elevates the pH of the emulsion to at least about 12, wherein the liquid solvent comprises seawater, the seawater comprising more than 32 wt % of the emulsion; and
incubating the emulsion to permit formation of nano- and micro-particles;
wherein the mixing of at least the pH control agent and the seawater further functions to ensure uniformity of diameters of the nano- and micro-particles, the diameters of the nano- and micro-particles being under 100 μm for substantially all of the nano- and micro-particles, and wherein the density of the nano-particles and micro-particles is 1.50 g/ml or less.
2. The method of claim 1 wherein the emulsion is incubated at about 30-150° C.
3. The method of claim 1 wherein the emulsion is incubated for about 5-200 minutes.
4. The method of claim 1 , wherein the liquid solvent further comprises: water, brine comprising monovalent, divalent, and multivalent salts, an alcohol comprising ethanol, propanol, butanol, or combinations thereof.
5. The method of claim 1 , wherein the at least one surfactant comprises anionic surfactants, cationic surfactants, nonionic surfactants, amphoteric surfactants or combinations thereof.
6. The method of claim 1 , wherein the particle-forming compound comprises aliphatic epoxides, anhydrides, glycidyl amine epoxide, cycloaliphatic epoxides, epoxy functional resins, polyurethane resins, phenol-formaldehyde resin, bis-phenol A diglycidyl ether, poly glycidyl ethers, acrylic resin, glycidyl ethers, bis-phenol F diglycidyl ethernovalac resins, or combinations thereof.
7. The method of claim 1 , wherein the at least one curing agent comprises isophorone diamine, boron tri-fluoride derivatives, imidazolines, mercaptans, hydrazides, polyamides, functional resins, mono ethanol amine, benzyl dimethylamine, lewis acids, tertiary amines, cycloaliphatic amines, amidoamines, aliphatic amines, aromatic amines, isophorone, imidazoles, sulfide, amides or their derivatives.
8. The method of claim 1 , wherein the pH control agent comprises sodium hydroxide, potassium hydroxide, or combinations thereof.
9. The method of claim 1 , further comprising:
adding a viscosity enhancer to the emulsion.
10. The method of claim 9 , wherein the viscosity enhancer comprises calcium carbonate nanoparticles, silicate nanoparticles, or water-soluble polymers comprising polyacrylamide or polyvinyl alcohol.