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This chapter discusses the methods used to characterize the microbial populations in oil reservoirs, to detect and control their detrimental activities such as souring and corrosion, and to stimulate their beneficial activities such as improved oil recovery. To be effective for enhanced oil recovery (EOR), the biosurfactant must reduce the interfacial tension between oil and brine by several orders of magnitude. Nitrite-reducing bacteria (NRB) can be placed in two functional groupings, the heterotrophic NRB (hNRB), and the nitrate- or nitrite-reducing, sulfide-oxidizing bacteria (NR-SOB). Samples to enumerate sulfate-reducing bacteria (SRB), general aerobic bacteria (GAB), or acid-producing bacteria (APB) should be taken at various points in the system, and the same sample should be used for the enumeration of each group of bacteria. The presence of SRB indicates a potential for corrosion and souring. The design of a microbially enhanced oil recovery (MEOR) process varies depending on the reservoir and problems that limits oil production. Oil reservoirs contain diverse and metabolically active microbial communities. Cultivation-dependent and cultivation-independent approaches can be used to characterize these communities and determine how their activities may affect operations. Knowledge of the potential microbial activities present in the surface facilities and the reservoir is critical to avoid the stimulation of unwanted microbial activities such as corrosion, souring, and biofouling during petroleum exploitation activities. This knowledge can also be used to stimulate the beneficial activities of microorganisms to improve oil recovery or alter the terminal electron-accepting process by nitrate addition. |
