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Keywords:

  • microbial oil recovery;
  • carbonate;
  • quartz;
  • porous media;
  • thermophilic;
  • Thermoanaerobacter

Abstract

Background

Several studies on oil recovery using a packed system have been reported; however, the majority use Berea (quartz). In Mexico, more than 37% of the proven reserves are found in reservoirs formed of carbonate and quartz rocks. In this study, the effects on microbial oil recovery of three types of porous media were evaluated: carbonate (Lm), quartz (Ot), and rock from a Mexican oil reservoir (Ch), formed of carbonate (45%) and quartz (38%).

Results

Oil recovery experiments using granulated porous media saturated with oil and two mixed cultures (AF1 and AF2) from a Mexican oil field, were assessed at 70°C under anaerobic conditions. Microbial cultures were composed of thermophilic, fermentative microorganisms, including Thermoanaerobacter, Natronovirga and Geothermobacterium, among others. Biomass production (150–240 mg L–1), substrate consumption (0.1 mg L–1 h–1) and CO2 production (0.10–0.28 mmol L–1) were measured. The systems presented significant differences in recovery (P= 0.000006), and carbonated systems presented the highest oil recovery; the best system combining the AF2 culture with porous medium from a Mexican reservoir (Ch) composed mainly of carbonate, achieving an oil recovery of 23.8%.

Conclusion

The efficiency of microbial enhanced oil recovery is dependent on the inoculum and the type of porous medium.