703 352 for example amine oxides amidoamine oxide surfactants may be suitable mixtures of zwitterionic surfactants and amphoteric surfactants may suitable an example is a mixture of about 13 isopropanol about 5 1 butanol about 15 ethylene glycol monobutyl ether about 4 sodium chloride about 30 water about 30 cocoamidopropyl betaine and about 2 cocoamidopropylamine oxide viscoelastic surfactant fluids for example those used in the oilfield may also contain agents that dissolve minerals and compounds for example in formations such as scale and filtercakes such agents may be for example hydrochloric acid formic acid acetic acid lactic acid glycolic acid sulfamic acid malic acid citric acid tartaric acid maleic acid methylsulfamic acid chloroacetic acid aminopolycarboxylic acids 3 hydroxypropionic acid polyaminopolycarboxylic acids for example trisodium hydroxyethylethylenediamine triacetate and salts of these acids and mixtures of these acids and or salts for sandstone treatment the fluid also typically contains a hydrogen fluoride source the hydrogen fluoride source may be hf itself or may be selected from ammonium fluoride and or ammonium bifluoride or mixtures of the two when strong acid is present the hf source may also be one or more of polyvinylammonium fluoride polyvinylpyridinium fluoride pyridinium fluoride imidazolium fluoride sodium tetrafluoroborate ammonium tetrafluoroborate salts of hexafluoroantimony teflon u2122 synthetic resinous fluorine containing polymer and mixtures when the formation dissolving agent is a strong acid the fluid preferably contains a corrosion inhibitor the fluid optionally contains chelating agents for polyvalent cations for example especially aluminum calcium and iron in which case the agents are often called iron sequestering agents to prevent their precipitation some of the formation dissolving agents just described are chelating agents as well chelating agents may be added at a concentration for example of about 0 5 of active ingredient when ves fluids contain strong acids.