1. Toluene Depletion in Produced Oil Contributes to Souring Control in a Field Subjected to Nitrate Injection.
- Author
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Agrawal, Akhil, Hyung soo Park, Nathoo, Safia, Gieg, Lisa M., Jack, Thomas R., Miner, Kirk, Ertmoed, Ryan, Benko, Aaron, and Voordouw, Gerrit
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PETROLEUM production , *HEAVY oil , *OIL field flooding , *PETROLEUM engineering , *NITRATES & the environment , *SULFATES , *CHEMICAL reduction , *PETROLEUM & the environment - Abstract
Souring in the Medicine Hat Glauconitic C field, which has a low bottom-hole temperature (30 °C), results from the presence of 0.8 mM sulfate in the injection water. Inclusion of 2 mM nitrate to decrease souring results in zones of nitrate-reduction, sulfate-reduction, and methanogenesis along the injection water flow path. Microbial community analysis by pyrosequencing indicated dominant community members in each of these zones. Nitrate breakthrough was observed in 2-PW, a major water- and sulfide-producing well, after 4 years of injection. Sulfide concentrations at four other production wells (PWs) also reached zero, causing the average sulfide concentration in 14 PWs to decrease significantly. Interestingly, oil produced by 2-PW was depleted of toluene, the preferred electron donor for nitrate reduction. 2-PW and other PWs with zero sulfide produced 95% water and 5% oil. At 2 mM nitrate and 5 mM toluene, respectively, this represents an excess of electron acceptor over electron donor. Hence, continuous nitrate injection can change the composition of produced oil and nitrate breakthrough is expected first in PWs with a low oil to water ratio, because oil from these wells is treated on average with more nitrate than is oil from PWs with a high oil to water ratio. [ABSTRACT FROM AUTHOR]
- Published
- 2012
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