A proppant material can include a core and an extended-release coating overlying the core. The extended release coating can include a polymer and an additive contained within the polymer.

Recover petroleum from a subterranean formulation by injecting an aqueous solution comprising a polyethylene oxide nonionic surfactants and a disulfonated anionic surfactant.

A wellbore fluid may include a gemini surfactant, a zwitterionic surfactant, an activator, and an aqueous base fluid. The gemini surfactant may have a structure represented by formula (I):

##STR00001##

where R.sup.1 is a C.sub.1-C.sub.10 hydrocarbon group, m and o are each, independently, an integer ranging from 1 to 4, and n is an integer ranging from 8 to 12.

The present invention discloses a composition for enhanced oil recovery comprising olefin sulfonate, sulfo-betaine, betaine and about 0.5 wt % to about 1.5 wt % magnesium chloride.

Surfactants are imbibed into Halloysite nanotubes (HNT) and the imbibed nanotubes are coated with wax on the nanotube outer surface. The wax layer prevents the surfactant from being disgorged from the HNT lumen until a triggering condition exists. Triggering conditions include contact with oil, which dissolves the wax; or exposure to temperatures above a melt transition of the wax, which causes the wax to melt. Upon exposure to a triggering condition, at least some of the imbibed surfactants are disgorged from the HNT and into the surrounding environment. The disgorged surfactants provide a conventional effect of reducing interfacial tension and changing reservoir rock wettability to enhance oil recovery. A range of surfactants and waxes are usefully employed in the compositions and methods described herein.

Enhanced oil recovery (EOR) including with a lamellar phase having Janus nanoparticles, petroleum surfactant, crude oil, and water and with additional water to give the flooding fluid that may be pumped through a wellbore into a subterranean formation to affect a property of hydrocarbon in the subterranean formation via contact of the flooding fluid with the hydrocarbon.

The invention discloses a core-shell structured anionic nano microemulsion system, and preparation and application thereof. The system comprises an anionic Gemini surfactant, an oil phase material, a solubilizer and water; wherein the microemulsion has a core-shell structure, with the outer shell being an anionic Gemini surfactant, and the inner core being an oil phase material. The anionic Gemini surfactant is N,N,N′,N′-dodecyl tetrasubstituted diphenyl ether sulfonate having the structural formula: ##STR00001## The anionic nano-microemulsion system of the present invention is homogeneous and transparent, has a spherical core-shell structure, has a nanometer size (3 to 40 nm) as droplets, has a narrow particle size distribution, is not easy to agglomerate, has good stability, and has an ultra-low interfacial tension and a capability of reducing viscosity of crude oil.

Methods for reducing scale deposition are provided. An exemplary method for reducing scale in an oilfield facility includes contacting a metallic surface with a production fluid including a film-forming surfactant selected from imidazolines, imidazolidines, amidoamines, isoxazolidines, fatty amines, α,β-unsaturated aldehydes, salts thereof, and combinations thereof, the production fluid including the film-forming surfactant in a concentration of at least about 200 ppm.

A method includes injecting an injection fluid through a well and to a depth of a formation, where the injection fluid includes phase-changing nanodroplets having a liquid core and a shell. The method also includes exposing the phase-changing nanodroplets to an external stimulus at the depth of the formation, wherein the liquid core of the phase-changing nanodroplets undergoes a liquid-to-vapor phase change causing the phase-changing nanodroplets to expand, and stimulating the formation at a near wellbore region by expansion of the phase-changing nanodroplets.

Enhanced oil recovery (EOR) including with a lamellar phase having Janus nanoparticles, petroleum surfactant, crude oil, and water and with additional water to give the flooding fluid that may be pumped through a wellbore into a subterranean formation to affect a property of hydrocarbon in the subterranean formation via contact of the flooding fluid with the hydrocarbon.