A method of drilling in a subterranean formation. A method may include providing a direct emulsion drilling fluid comprising an aqueous fluid, an oil, and a polysorbate emulsifier; circulating the direct emulsion drilling fluid from a surface, through a wellbore, and back to the surface; and extending the wellbore in the subterranean formation while circulating the direct emulsion drilling fluid.

The present invention relates to aqueous compositions for forming a foam, comprising a surfactant and a particulate inorganic material, and optionally one or more polymers, such as soil conditioning polymers, and/or viscosity increasing polymers. The present invention further relates to the use and application of said aqueous compositions.

A method includes injecting an aqueous-based injection fluid into a wellbore at a first temperature, where the aqueous-based injection fluid includes phase-changing nanodroplets having a liquid core and a shell. The method also includes exposing the phase-changing nanodroplets to a second temperature in the wellbore that is greater than or equal to a boiling point of the liquid core to change a liquid in the liquid core to a vapor phase and expand the phase-changing nanodroplets, thus removing debris from the wellbore and surrounding area.

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.

Amidoamine-based gemini surfactants having dual chains connected via an alkenylene or alkynylene linker. Each chain contains a quaternary ammonium head group and an ethoxylated alkyl tail. A water-based drilling fluid containing the gemini surfactant is also provided. As examined by linear swelling and free swelling tests, the gemini surfactant is effective in reducing clay swelling.

A method of removing calcium-containing water-based filter cake from a wellbore involving contacting the calcium-containing filter cake with a biodegradable acid solution of water, hydrochloric acid, formic acid, citric acid, and a surfactant. The method is performed at a pressure of 200 to 400 psi and a temperature of 50 to 125° C. The method removes calcium-containing filter cake made of water, calcium carbonate, a polymer or starch and a clay. The method meets industry standard steel corrosion rates of less than 0.049 lb/ft.sup.2 per day. Also disclosed is a biodegradable acid solution of water, hydrochloric acid, formic acid, citric acid, and a surfactant that meets OECD 301B thresholds for ready biodegradability.

A nonionic Gemini surfactant, (octylphenol polyoxyethylene ether disubstituted) dicarboxylic acid diphenyl ether has a structural formula of: ##STR00001##
and is prepared by a two-step reaction: S1, diphenyl ether 4,4′-dicarboxylic acid is subjected to an acyl chlorination reaction to obtain diphenyl ether 4,4′-dicarbonyl dichloride; S2, diphenyl ether 4,4′-dicarbonyl dichloride is subjected to an esterification reaction with octylphenol polyoxyethylene ether (OP-10) to obtain the target product (octylphenol polyoxyethylene ether disubstituted) dicarboxylic acid diphenyl ether. The surfactant is expected to be applied in tertiary oil recovery as an alkali/surfactant, in polymer/surfactant binary composite flooding, in alkali/surfactant/polymer ternary composite flooding, as a microemulsion emulsifier and the like, and it can also be compounded with a common surfactant to reduce the use cost, and thus create conditions for its large-scale application.

The anionic cocogem surfactant of formula (I) for an oil production process of increased efficiency ##STR00001##
wherein each R1 and R2 is independently selected from hydrogen or C1-C18 straight or branched alkyl optionally substituted by OH; each R3 is independently selected from hydrogen; C1-C25 straight or branched alkyl or alkenyl optionally comprising inter-chain amido-group; aromatic group optionally substituted by C1-C25, preferably C5-C20, more preferably C5-C15 straight or branched alkyl, preferably selected from phenyl and diphenylether; or C10-C20 straight or branched alkenyl, alkadienyl or alkatrienyl; Z is C1-C18 straight or branched alkylene optionally substituted by one or two C1-C6 alkyl or preferably C3-C6 cycloalkyl, optionally comprising (EO).sub.n and/or (PO).sub.m groups, wherein EO is ethylene-oxide i.e. —CH.sub.2CH.sub.2O—, and PO is propylene-oxide, i.e. —CH(CH.sub.3)CH.sub.2O—, wherein n and m is independently an integer of from 0 to 30 and n+m is an integer of from 1 to 30; and/or [NH(R4)].sup.+ quaternary ammonium, wherein R4 is hydrogen, C1-C6 alkyl, preferably methyl or ethyl; R5 is hydrogen or C1-C6 alkyl, preferably methyl or ethyl; An is one or more groups selected from SO.sub.3.sup.−, Cl.sup.− or CO.sub.2.sup.−; i is an integer of 0 or 1; p is an integer of 2 or 3; j is an integer of 2 or 3.

The present invention discloses a N,N,N′,N′-tetradodecyl-substituted diphenyl ether sulfonate anionic Gemini surfactant and the synthesis method thereof. It has a structural formula of: ##STR00001## and is prepared in a two-step reaction comprising: S1. subjecting 4,4′-diaminodiphenyl ether and bromododecane to an amine alkylation reaction to obtain N,N,N′,N′-tetradodecyl-substituted diphenyl ether; and S2. sulfonating the N,N,N′,N′-tetradodecyl-substituted diphenyl ether with concentrated sulfuric acid to produce the target product, N,N,N′,N′-tetradodecyl-substituted diphenyl ether sulfonate. The surfactant of the present invention has a high surface activity and can be synthesized with a simple procedure under mild reaction conditions, and can be easily separated and purified. The surfactant of the present invention is promising in applications for alkaline/surfactant in tertiary oil recovery, for polymer/surfactant binary compound flooding, alkaline/surfactant/polymer tertiary compound flooding, microemulsion emulsifier, and the like, and may also be compounded with common surfactants to lower the cost, thereby enabling its application in a large scale.

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.