Control of hydrogen sulfide in oil and gas wells with nitrite injection

摘要

The downhole injection of nitrite-containing solutions into sour oil and gas wells under controlled conditions has been observed to effectively remove hydrogen sulfide (H sub 2S) from aqueous and gas phases. Souring control using nitrite has been successfully applied to a gas well in the San Juan Basin of New Mexico and to an oil well in the Amoco Netherlands Rijnfield. H sub 2 S removal from topsides water separations equipment was also facilitated using nitrite. Injected nitrite (NO sub 2) scavenges H sub 2 S and prevents the activity of sulfatereducing bactria while it is present. H sub 2 S production from oil or gas wells treated with nitrite may be suppressed for much longer periods of time. In a 36-hour downhole squeeze in a gas well, injected NO sub 2 removed H sub 2 S from produced gas for a period of 7 months. SRB populations in produced fluids were reduced for a period of 3 months following treatment. In an oil dehydrator, the addition of NO sub 2 during regular operation resulted in a decrease in aqueous-phase H sub 2 S from 40-60mg/l to less than 1 mg/l. Corrosion rate data indicated a less corrosive environment during the NO sub 2 decreased H sub 2 S in associated gas from 140 ppm to less than 1 ppm for 60 days following treatment. H sub 2 S levels remained below pre-injection levels for 6 months following treatment. Oil production increased immediately following the treatment, probably due to the dissolution of precipitated iron sulfides in the zone surrounding the well bore. This treatment has proven an effective means of controlling H sub 2 S in oil and gas wells as well as a method of removing iron sulfide scale from the near well-bore.