Oil-field biocide method utilizing a peracid
View Patent ↗Aqueous well treatment fluid compositions with biocidal activity are disclosed comprising a polymer for modifying fluid viscosity in the aqueous fluid, an organic monocarboxylic peracid being present in an anti-microbial amount of about 1 ppm to about 1000 ppm, and a controlled amount of hydrogen peroxide also being present. Peracetic acid is the preferred peracid. The viscosity-modifying polymer in the aqueous well treatment fluid composition may serve to reduce friction in the fluid or increase fluid viscosity. A method of using such compositions is also disclosed.
1. A method of providing biocidal activity in a well treatment fluid comprising
introducing, into an aqueous well treatment fluid composition comprising a polymer or copolymer for modifying fluid viscosity, wherein the polymer or copolymer is selected from the group consisting of acrylamide derived polymers and copolymers; acrylate derived polymers and copolymers; guar and guar derivatives; ethylene oxide-derived polymers, and combinations of these, an aqueous peracetic acid solution in an amount sufficient to provide an antimicrobial-effective amount of about 1 ppm to about 1000 ppm peracetic acid, the aqueous peracetic acid solution having a peracetic acid weight concentration of about 15-17 wt % and hydrogen peroxide concentration of about 9-11 wt %; and thereafter
directing the aqueous well treatment fluid into a subterranean environment susceptible to contamination by sulfur-reducing bacteria.
2. The method of claim 1 wherein the aqueous peracetic acid solution is introduced in an amount sufficient to provide about 1 ppm to about 50 ppm peracetic acid.
3. The method of claim 1 wherein the aqueous peracetic acid solution is introduced into the aqueous well treatment fluid composition when the composition has a pH less than about 8.
4. The method of claim 1 wherein the aqueous peracetic acid solution is introduced into water used to prepare the aqueous well treatment fluid composition.
5. The method of claim 1 wherein the polymer or copolymer serves to reduce fluid viscosity and is present in a friction-reducing amount to provide improved fluid flow characteristics.
6. The method of claim 5 wherein the friction-reducing polymer or copolymer is present in an amount of about 0.01 wt % to about 1 wt %, based on the weight of the aqueous composition.
7. The method of claim 1 wherein the polymer or copolymer serves to increase fluid viscosity and is present in an amount sufficient to provide increased fluid viscosity.
8. The method of claim 7 wherein the viscosity-increasing polymer or copolymer is selected from the group consisting of acrylamide-derived polymers and copolymers; acrylate-derived polymers and copolymers; natural and synthetic polysaccharides and their derivatives; natural and synthetic cellulosic polymers and copolymers and their derivatives; and combinations of these.
9. The method of claim 8 wherein the viscosity-increasing polymer or copolymer is at least partially crosslinked.
10. The method of claim 7 wherein the viscosity-increasing polymer is present in an amount of about 0.1 wt % to about 10 wt %, based on the weight of the aqueous composition.
11. The method of claim 1 wherein the sulfur-reducing bacteria is selected from the group consisting of Desulfovibrio species and Desulfotomaculum species.