MEOR in Northwest Peru
Authors: Bybee Karen 
Published: February 2015

This article, written by Assistant Technology Editor Karen Bybee, contains highlights of paper SPE 94934, "Biotechnology Application to EOR in Talara Offshore Oil Fields, Northwest Peru" by A. Maure, Microbes Inc., and A.A. Saldana, SPE, and A.R. Juarez, SPE, Petro-Tech Peruana S.A., prepared for the 2005 SPE Latin American and Caribbean Petroleum Engineering Conference, Rio de Janeiro, 20–23 June.
Seven producing wells in the Providencia and Lobitos fields of Block Z-2 in the Talara basin were selected to evaluate a biotechnology approach for enhanced oil recovery (EOR). The microbial-EOR (MEOR) candidates produce from faulted reservoirs by intermittent gas lift methods. The oils are paraffinic and present good candidates for biotreatability. Because of operational reasons not directly related to MEOR, the complete inoculation program was concluded in only four of the original seven wells.

Biotechnology
Biotechnology methods are founded in the use of sophisticated enzyme biochemistry to accelerate redox reactions that involve different hydrocarbon compounds. MEOR technology in the upstream sector is based on the systematic inoculation of producers and/or injectors with specific microbial systems, biocatalyzers, and nutrients. The pulsing program pursues as its primary goal the colonizing of the porous medium of the oil-bearing zones. The second objective is to control enzymatic reactions at water/oil interfaces in the producing formation to modify oil mobility by producing low-molecular-weight solvents and biosurfactants. Organic geochemistry methods monitor the stability and efficiency of these bioreactions.
Producer Wells. Producer wells are treated by periodically pumping microbial batches downhole to reach the near-wellbore porous space. The microbial effect in treated wells benefits production in two ways. It removes organic damage occurring near the wellbore of the perforated interval to open nonproductive zones containing oils with a heavier and pseudoplastic behavior. This effect produces a high peak oil rate for a limited time. These treatments can produce permanent rheological effects by the compositional alteration that occurs at a larger colonization radius. This effect is the most important MEOR objective because this improvement is sustainable for a long period if a proper microbial inoculation schedule is continued.
Injector Wells. In injector wells, the treatment uses the injected water as a carrier to introduce microorganisms and passive substances into active streamtubes of flooded space for target layers. Compared to the producer treatments, the advantage of treating injectors is a larger size of colonized zones with longer residence times.
Biocracking. Biocracking is based on a systematic way to alter n-alkane compositional profiles in oils. The use of enzyme biochemistry accelerates the redox reactions involving linear hydrocarbons. Heavy paraffinic compounds can be transformed into shorter ones by the enzymatic action of repetitive cycles, which are assisted by symbiotic microorganisms and specific nutrients. By alternating aerobic/facultative hemicycles with strictly anaerobic, the time-coordinated action of selected groups of microorganisms in oxidant and reductive environments results in a substantial shift in oil compositional profile.