Biotecnologia aplicada à recuperação avançada de petróleo: injeção de biossurfactantes.

Abstract

Surfactants have been used in the enhanced oil recovery of mature reservoirs. Injection of surfactants are used to alter rock wettability and reduce interfacial tension between oil and water, increasing the oil recovery factor of the reservoir. The increased demand for green technologies has boosted the world market for biosurfactants and stimulated research for new compounds. In this context, this study evaluated the tensoactive properties of biosurfactants produced by previously isolated bacteria from Ceará mangrove sediments, towards future applications in enhanced oil recovery (MEOR). A guided screening selected 14 biosurfactant-producing strains, identified as Bacillus. The purified biosurfactants were characterized by infrared spectroscopy, differential scanning calorimetry and mass spectrometry, their tensioactive properties were measured under extreme conditions of temperature, salinity and pressure and evaluated for ecotoxicity. The biosurfactants were confirmed as lipopeptides of the surfactin, iturin and fengycin families. A new compound of m/z 1629 with de-emulsifying activity was also detected. Eight strains have been shown to produce predominantly isoforms of surfactin, being considered one of the most potent biosurfactants known, and six for producing bacilomycin and iturins. All retained surface tension reduction, emulsification and oil dispersion activity after 121 °C/15 min and pressure of 600 bar. The determination of the critical micelle concentration of twelve of these surfactants ranged from 5.34 to 26.78 mg/L. Nine of these products formed stable water/oil emulsions in the presence of 100-150 g/L NaCl and all supported temperatures up to 250 °C. Among the fourteen biosurfactants, twelve were able to invert the wettability of carbonaceous rock at 50 mg/L, surpassing the synthetic surfactant sodium dodecyl sulfate (SDS). The biosurfactants did not present toxicity against Artemia salina nauplii. Based on the values of emulsification, surface tension reduction and inversion of wettability, summed to the stability under conditions of salinity, temperature and pressure commonly found in carbonate reservoirs, in this study two the biosurfactants produced by TIM 03 and TIM 96, identified as B. amyloliquefaciens, and ICA 24, identified as B. vallismortis, stood out towards ex situ MEOR applications.