Comportamento fisiológico e morfológico de microrganismos provenientes de reservatórios de petróleo offshore brasileiros submetidas à alta pressão hidrostática

Abstract

The application of seawater for secondary oil recovery leads to the development of sulfate-reducing bacteria in oil fields, leading to microbial corrosion of steel equipment and acidification of oil. In order to evaluate the effect of high hydrostatic pressure on growth, sulfate-reducing activity and on the ultrastructure of these microorganisms, two mixed cultures from offshore reservoirs off the Brazilian coast were used, one from injection water collected at a depth of 100 m (BTB0119) and the other of production water, at 3,060 m (BTB0419), and a pure culture of Desulfovibrio alaskensis. The samples were morphologically characterized by Scanning Electron Microscopy and their complexity and size by Flow Cytometry. The cultures were submitted to two piezo-treatments: 35 and 65 MPa for 20 hours followed by 28 days at 0.1 MPa, and 35 and 65 MPa for 28 days. Visible light spectroscopy and the “Most Likely Number” evaluation method were used to measure bacterial concentration. It was observed that bacterial concentration values obtained using optical spectroscopy were more accurate and realistic than those obtained using the most likely number methodology. It was also observed that at ambient pressure the growth profile of the pure culture was similar to that of BTB0419 and different from that of BTB0119. The cultures showed different growth profiles as a function of the applied pressure. All cultures showed a high sulfate reducing activity at 0.1 MPa, decreasing with increasing pressure. Therefore, understanding the role that high pressure exerts on bacterial cultures growth can provide important information about the problems caused by their activity. This work intends to elucidate some issues that can improve acidification and corrosion treatment strategies of materials used in oil production in deep waters.