Invert emulsions may be used in downhole operations to delay the swelling of water-swellable polymers. For example, a treatment fluid may be introduced into a wellbore penetrating a subterranean formation, the treatment fluid comprising an emulsion with an continuous oil phase and a discontinuous aqueous phase, an emulsifier, and a water-swellable polymer suspended in the continuous oil phase, wherein the aqueous discontinuous phase has a pH of about 0 to about 11; the emulsion may be broken while the treatment fluid in a portion of the subterranean formation; and the water-swellable polymer may be swollen into a swollen polymer, thereby reducing fluid flow through the portion of the subterranean formation. In some instances, for carbonate subterranean formation, the aqueous discontinuous phase may have a pH of about 7 to about 11.

Invert emulsions may be used in downhole operations to delay the swelling of water-swellable polymers. For example, a treatment fluid may be introduced into a wellbore penetrating a subterranean formation, the treatment fluid comprising an emulsion with an continuous oil phase and a discontinuous aqueous phase, an emulsifier, and a water-swellable polymer suspended in the continuous oil phase, wherein the aqueous discontinuous phase has a pH of about 0 to about 11; the emulsion may be broken while the treatment fluid in a portion of the subterranean formation; and the water-swellable polymer may be swollen into a swollen polymer, thereby reducing fluid flow through the portion of the subterranean formation. In some instances, for carbonate subterranean formation, the aqueous discontinuous phase may have a pH of about 7 to about 11.

Some embodiments of the present disclosure provide a method for preparing a self-phase change proppant based on an emulsified and toughened bio-based epoxy resin. Toughening modification is performed on the bio-based epoxy resin by graphite particles, and then the bio-based epoxy resin after the toughening modification is emulsified by SiO.sub.2 particles as an emulsifier to prepare the self-phase change proppant; a proportion of different mesh numbers in the self-phase change proppant is adjusted by changing a concentration of the emulsifier during emulsification; and the chemical formula of the bio-based epoxy resin is: ##STR00001##
The proppant particles in the present disclosure have good sphericity and high fracture permeability after being laid, which can effectively extract the remaining oil in the fractures, thus improving the development efficiency of the oilfield.

Some embodiments of the present disclosure provide a method for preparing a self-phase change proppant based on an emulsified and toughened bio-based epoxy resin. Toughening modification is performed on the bio-based epoxy resin by graphite particles, and then the bio-based epoxy resin after the toughening modification is emulsified by SiO.sub.2 particles as an emulsifier to prepare the self-phase change proppant; a proportion of different mesh numbers in the self-phase change proppant is adjusted by changing a concentration of the emulsifier during emulsification; and the chemical formula of the bio-based epoxy resin is: ##STR00001##
The proppant particles in the present disclosure have good sphericity and high fracture permeability after being laid, which can effectively extract the remaining oil in the fractures, thus improving the development efficiency of the oilfield.

A method of extracting underground resources including a step of mixing hydrolysable particles and a proppant to an aqueous dispersion fluid, and introducing the fluid with pressure into an ore chute formed under the ground, wherein as the hydrolysable particles, use is made of spherical particles that include a hydrolysable resin of a weight average molecular weight (Mw) of not less than 5,000 and, specifically, not less than 10,000, and that have an average particle size (D.sub.50) in a range of 300 to 1,000 μm, and a circularity of a short diameter/long diameter ratio of not less than 0.8. The spherical particles have a hyrolysable capability, a circularity and a particle size adapted to the hydraulic fracturing.

A method of extracting underground resources including a step of mixing hydrolysable particles and a proppant to an aqueous dispersion fluid, and introducing the fluid with pressure into an ore chute formed under the ground, wherein as the hydrolysable particles, use is made of spherical particles that include a hydrolysable resin of a weight average molecular weight (Mw) of not less than 5,000 and, specifically, not less than 10,000, and that have an average particle size (D.sub.50) in a range of 300 to 1,000 μm, and a circularity of a short diameter/long diameter ratio of not less than 0.8. The spherical particles have a hyrolysable capability, a circularity and a particle size adapted to the hydraulic fracturing.

A method for controlling fluid loss into the pores of an underground formation during fracturing operations is provided. Nanoparticles are added to the fracturing fluid to plug the pore throats of pores in the underground formation. As a result, the fracturing fluid is inhibited from entering the pores. By minimizing fluid loss, higher fracturing fluid pressures are maintained, thereby resulting in more extensive fracture networks. Additionally, nanoparticles minimize the interaction between the fracturing fluid and the formation, especially in water sensitive formations. As a result, the nanoparticles help maintain the integrity and conductivity of the generated, propped fractures.

A method for controlling fluid loss into the pores of an underground formation during fracturing operations is provided. Nanoparticles are added to the fracturing fluid to plug the pore throats of pores in the underground formation. As a result, the fracturing fluid is inhibited from entering the pores. By minimizing fluid loss, higher fracturing fluid pressures are maintained, thereby resulting in more extensive fracture networks. Additionally, nanoparticles minimize the interaction between the fracturing fluid and the formation, especially in water sensitive formations. As a result, the nanoparticles help maintain the integrity and conductivity of the generated, propped fractures.

A composite particle that incorporates a material and is designed to undergo a reaction and/or mechanical or chemical change with the environment to increase in volume. The composite particle can be combined with a constraining matrix to create an expandable particle upon reaction. These particles can be used in stimulating wells, including oil and gas reservoirs.

A composite particle that incorporates a material and is designed to undergo a reaction and/or mechanical or chemical change with the environment to increase in volume. The composite particle can be combined with a constraining matrix to create an expandable particle upon reaction. These particles can be used in stimulating wells, including oil and gas reservoirs.