title: Souring in low-temperature surface facilities of two high-temperature Argentinian oil fields.
abstract: Produced waters from the Barrancas and Chihuido de la Salina (CHLS) fields in Argentina had higher concentrations of sulfate than were found in the injection waters, suggesting that the formation waters in these reservoirs had a high sulfate concentration and that sulfate-reducing bacteria were inactive downhole. Incubation of produced waters with produced oil gave rapid reduction of sulfate to sulfide (souring) at 37 °C, some at 60 °C, but none at 80 °C. Alkylbenzenes and alkanes served as electron donor, especially in incubations with CHLS oil. Dilution with water to decrease the ionic strength or addition of inorganic phosphate did not increase souring at 37 or 60 °C. These results indicate that souring in these reservoirs is limited by the reservoir temperature (80 °C for the Barrancas and 65-70 °C for the CHLS field) and that souring may accelerate in surface facilities where the oil-water mixture cools. As a result, significant sulfide concentrations are present in these surface facilities. The activity and presence of chemolithotrophic Gammaproteobacteria of the genus Thiomicrospira, which represented 85% of the microbial community in a water plant in the Barrancas field, indicated reoxidation of sulfide and sulfur to sulfate. The presence of these bacteria offers potential for souring control by microbial oxidation in aboveground facilities, provided that formation of corrosive sulfur can be avoided.
authors.affiliation: Petroleum Microbiology Research Group, Department of Biological Sciences, University of Calgary, 2500 University Dr. NW, Calgary, T2N 1N4, Alberta, Canada.
authors.forename: Akhil
authors.initials: A
authors.lastname: Agrawal
authors.forename: Dongshan
authors.initials: D
authors.lastname: An
authors.forename: Adriana
authors.initials: A
authors.lastname: Cavallaro
authors.forename: Gerrit
authors.initials: G
authors.lastname: Voordouw
mesh_terms: D001118:Argentina; D001419:Bacteria / Q000302:isolation & purification / Q000378:metabolism; D061329:Oil and Gas Fields / Q000382:microbiology*; D013431:Sulfates / Q000378:metabolism; D013440:Sulfides / Q000378:metabolism; D013696:Temperature
chemical_list: D013431:Sulfates; D013440:Sulfides