HYDROCHLORIC ACID COMPOSITIONS AND THEIR USE

摘要

The invention provides a thickened aqueous hydrochloric acid composition comprising (a) 1 to 20% w hydrogen chloride, (b) an alcohol ethoxylate of general formula R-O-CH2-CH2-O)nH wherein R is a C8-20 alkyl group and n has an average value in the range 3 to 15, provided that the (CH2-CH2-O)n moiety constitutes 50 to 67% w of the alcohol ethoxylate, (c) an alkyl aryl sulfonic acid of general formula II wherein R1 is a C8-13 linear alkyl chain and R2 and R3 independently hydrogen atoms or methyl groups, the combined concentration of (b) and (c) being in the range 3 to 15% w, the relative weight proportions of (b) and (c) being in the range 45 to 65% of (b) to 55 to 35% of (c), and (d) 0 to 2% w of a salicylate of general formula where R4 is a C1-4 alkyl or a benzyl group. The compositions may be used as lime scale removers or in acid treatment of subterranean formations surrounding oil or gas wells.