Toluene Depletion in Produced Oil Contributes to Souring Control in a Field Subjected to Nitrate Injection

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• 作者：Akhil Agrawal ; Hyung soo Park ; Safia Nathoo ; Lisa M. Gieg ; Thomas R. Jack ; Kirk Miner ; Ryan Ertmoed ; Aaron Benko ; Gerrit Voordouw
• 刊名：Environmental Science & Technology (ES&T)
• 出版年：2012
• 出版时间：January 17, 2012
• 年：2012
• 卷：46
• 期：2
• 页码：1285-1292
• 全文大小：386K
• 年卷期：v.46,no.2(January 17, 2012)
• ISSN：1520-5851

文摘

Souring in the Medicine Hat Glauconitic C field, which has a low bottom-hole temperature (30 掳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.