Diluted microemulsions with low surface tensions

Abstract

Compositions relating to microemulsions or diluted microemulsions for treating gas wells having wellbores and methods related to treating gas wells having wellbores using the same are generally provided. In some embodiments, the microemulsions or diluted microemulsions have an especially low surface tension at a gas well bottom hole temperature and pressure.

What is claimed is: 
     
         1 . A microemulsion suitable for treating a gas well, comprising:
 an aqueous phase;   a surfactant; and   a non-aqueous phase comprising a combination of solvents comprising a first solvent and a second solvent,   wherein the first solvent comprises a methylated cyclic alkane solvent and/or a methyl siloxane solvent of less than or equal to 800 g/mol molecular weight; and   wherein the second solvent comprises a terpene, an alkyl aliphatic carboxylic acid ester, an unsaturated hydrocarbon solvent, an aromatic solvent, a dialkyl ether, a bicyclic hydrocarbon solvent, a C 6 -C 10  linear or branched alkane solvent, and/or an alcohol.   
     
     
         2 . The microemulsion of  claim 1 , wherein the first solvent comprises the methyl siloxane solvent of less than or equal to 800 g/mol molecular weight. 
     
     
         3 . The microemulsion of  claim 1 , wherein the second solvent comprises the terpene, and the terpene comprises d-limonene, dipentene, alpha terpineol, alpha-pinene, beta-pinene, alpha-terpinene, alpha-terpinyl acetate, menthone, cineole, citranellol, carvone, linanool, geraniol, nopol, menthol, eucalyptol, 1,8-cineol, a terpene containing an aldehyde, a terpene containing an ether, and/or a terpene containing a ketone. 
     
     
         4 . The microemulsion of  claim 1 , wherein the second solvent comprises the alkyl aliphatic carboxylic acid ester, and the alkyl aliphatic carboxylic acid ester comprises butyl 3-hydroxybutyrate, isopropyl 3-hydroxybutyrate, hexyl 3-hydroxylbutyrate, methyl octanoate, and/or methyl decanoate. 
     
     
         5 . The microemulsion of  claim 1 , wherein the second solvent comprises the aromatic solvent, the dialkyl ether, the bicyclic hydrocarbon solvent, and/or the unsaturated hydrocarbon solvent, wherein the unsaturated hydrocarbon solvent comprises an unsubstituted acyclic branched alkene or unsubstituted acyclic unbranched alkene having one or two double bonds and from 6 to 12 carbon atoms. 
     
     
         6 . The microemulsion of  claim 1 , wherein the second solvent comprises the alcohol, and the alcohol comprises a primary, secondary, or tertiary alcohol having from 1 to 20 carbon atoms. 
     
     
         7 . The microemulsion of  claim 1 , wherein the second solvent comprises the C 6 -C 10  linear or branched alkane solvent, and wherein the C 6 -C 10  linear or branched alkane solvent comprises hexane, heptane, octane, isooctane, nonane, decane, isomers of methylpentane, isomers of dimethylpentane, isomers of trimethylpentane, and/or 4-methylheptane. 
     
     
         8 . The microemulsion of  claim 1 , wherein the second solvent comprises the C 6 -C 10  linear or branched alkane solvent and the alcohol. 
     
     
         9 . The microemulsion of  claim 1 , wherein the microemulsion further comprises an additive. 
     
     
         10 . The microemulsion of  claim 9 , wherein the additive comprises a demulsifier, a freezing point depression agent, a proppant, a scale inhibitor, a friction reducer, a biocide, a corrosion inhibitor, a buffer, a viscosifier, an oxygen scavenger, a clay control additive, a paraffin control additive, an asphaltene control additive, an acid, an acid precursor, and/or a salt. 
     
     
         11 . The microemulsion of  claim 10 , wherein the additive comprises the demulsifier. 
     
     
         12 . The microemulsion of  claim 11 , wherein the demulsifier comprises an alkoxylated novolac resin, alkoxylated polyimine, and/or alkoxylated polyamine. 
     
     
         13 . The microemulsion of  claim 1 , wherein the first solvent comprises the methylated cyclic alkane solvent, and the methylated cyclic alkane solvent comprises methylcyclopentane, dimethylcyclopentane, methylcyclohexane, dimethylcyclohexane, trimethylcyclohexane, methylcycloheptane, and/or isopropylcyclohexane. 
     
     
         14 . The microemulsion of  claim 1 , wherein the first solvent comprises the methyl siloxane solvent of less than or equal to 800 g/mol molecular weight, and the methyl siloxane solvent of less than or equal to 800 g/mol molecular weight comprises hexamethyldisiloxane, octamethyltrisiloxane, decamethyltetrasiloxane, dodecamethylpentasiloxane, tetradecamethylhexasiloxane, hexadecamethylheptasiloxane, octamethylcyclotetrasiloxane, decamethylcyclopentasiloxane trimethylsiloxy-terminated 2 cSt polydimethylsiloxane, and/or trimethylsiloxy terminated 3 cSt polydimethylsiloxane. 
     
     
         15 . The microemulsion of  claim 1 , wherein the surfactant comprises a nonionic surfactant. 
     
     
         16 . The microemulsion of  claim 15 , wherein the nonionic surfactant comprises an alkyl glycoside, alkyl glucamide, alkoxylated alcohol, alkoxylated fatty alcohol, alkoxylated castor oil, alkoxylated fatty acid, alkoxylated tristyryl phenol containing from 6 to 100 total ethylene oxide (EO) and propylene oxide (PO) units, and/or alkoxylated fatty amide with a hydrocarbon chain of at least 8 carbon atoms and 5 units or more of alkoxylation. 
     
     
         17 . The microemulsion of  claim 1 , wherein:
 the first solvent comprises the methyl siloxane solvent of less than or equal to 800 g/mol molecular weight;   the second solvent comprises the C 6 -C 10  linear or branched alkane solvent and the alcohol; and   the surfactant comprises a nonionic surfactant.   
     
     
         18 . The microemulsion of  claim 1 , wherein the surfactant comprises an anionic surfactant and/or a cationic surfactant. 
     
     
         19 . The microemulsion of  claim 1 , wherein the surfactant comprises a zwitterionic surfactant. 
     
     
         20 . A method of treating a gas well having a wellbore, comprising:
 injecting the microemulsion of  claim 1  or a diluted version thereof into the wellbore,   wherein the combination of solvents has a vapor pressure of less than or equal to 150 mm Hg at the gas well temperature and pressure and/or a surface tension of less than or equal to 34 mN/m and greater than or equal to 15 mN/m at the temperature and pressure of the gas well.