| abstract |
An aqueous wash composition suitable for the clean-up of drilling and completion fluid filtercakes comprises water and an effective amount of cationic salts of polyaminocarboxylic acids at neutral or acidic pH. The wash may further comprise an enzyme or oxidiser. Cationic salts of polyaminocarboxylic acids suitable include (ethylenedinitrilo) tetraacetic acid, ethylenediaminetetraacetic acid (EDTA), cyclohexylene dinitrilo tetraacetic acid (CDTA), [ethylenebis(oxyethylenenitrilo)] tetraacetic acid (EGTA, also known as ethyleneglycol- bis-(beta-aminoethyl ether) N,N' -tetraacetic acid) and [[(carboxymethyl)imino]-bis (thylenenitrilo)]-tetraacetic acid (DTPA, also known as diethylenetriaminepenta-acetic acid). Preferably the cation is potassium and the pH in the range 4.7 to 5.5. |