PERMEABILITY CONTRAST CORRECTION EMPLOYING A SULFATE-FREE PROPIONATE-SEQUESTERED CHROMIUM(III)SOLUTION

摘要

A sulfate-free clear green solution of chromium(III) propionate is prepared by mixing aqueous propionic acid containing up to 55 weight percent propionic acid with a chromium(VI) oxidant, such as a dichromate or chromate, and a sulfur-containing reductant, such as a bisulfite, which on reacting yields two phases: a lower sulfate-containing phase for discard or recycle and an upper phase solution of sulfate-free clear green propionate-sequestered chromium(III), the latter phase being stabilized with additional acid. The upper phase solution is useful for crosslinking polymeric viscosifiers such as partially hydrolyzed acrylamide-based polymers and the like in permeability contrast corrections in enhanced oil recovery operations.