HC-0C-03: Biological Treatments to Improve the Quality of Heavy Crude Oils

Petroleum or crude oil is a crucial source of energy and one of the main factors driving the World’s economy. The progressive depletion of high-quality crudes in the last decades will make necessary the exploitation of unconventional low-quality heavy and extra-heavy crudes to meet future energy demands. However, their exploitation requires the application of special techniques in order to facilitate their recovery, transportation and refining. Chemical and thermal methods commonly employed (e.g. use of gases, polymers or solvents; hydraulic fracturing; in situ combustion) are expensive and environmentally hazardous. The application of biological treatments to reduce the viscosity and density of unconventional oils can be a cheaper and environmentally friendly alternative or a complementary technology. The bioconversion of crude oil is a process where heavy oil fractions are converted into lighter ones due to the action of microorganisms or enzymes, resulting in an enrichment in lighter hydrocarbons. However, it is necessary to select microorganisms and enzymes with the ability of degrading preferentially the heavy oil fractions (long chain alkanes, aromatics, resins and asphaltenes). As a result, the oil viscosity is reduced (usually from 10³–10² cP up to 10 cP) and its mobility is improved, which contributes to increase oil recovery efficiency and, at the same time, increases the quality of the oil. This chapter will review the latest advances in the use of biological treatments to reduce the viscosity and improve the quality of heavy crude oils.