Use of Microorganisms in the Biotechnology for the Enhancement of Oil Recovery

Abstract

The existing methods of oil field exploitation give the opportunity to extract no more than half of the geological resources of oil; from carbonate oil collectors, only 20% of oil is extracted [1]. Furthermore, the portion of recovered oil is tending to decrease due to the development of deposits of viscous oils under difficult geological and physical conditions. Thus, new methods for enhancing oil recovery are needed to at least maintain oil extraction at a constant level. There are various chemical and physicochemical methods for enhancing oil recovery. The method of secondary flooding, developed by the Soviet academician A.P. Krylov in the 1930s, is widely used in many oilproducing countries. Surface water is pumped into the oil stratum through a system of water-injection wells, which results in an increase in the stratal pressure. This technology is highly efficient. Chemical methods, used in combination with secondary flooding, belong to the so-called tertiary methods of oil recovery enhancement. These include immiscible flooding (alkaline or polymeric) and miscible flooding with solvents and acids, as well as flooding with the use of surface-active compounds (surfactant flooding, or microemulsion flooding). The surfactants widely used in Europe and North America are chemically synthesized oil sulfonates. Gas injection is also applied, with CO 2 , N 2 , and hydrocarbon gases being mainly used. Thermal methods include injection of a heat carrier (hot water or vapor) or intrastratal combustion. Selective plugging of highly permeable layers for the improvement of flooding is little used in Europe and Siberia but is widely applied in North America, Canada in particular [2]. The development of methods for microbial enhancement of oil recovery started in the middle of the 20th century. They are highly efficient and diverse, environmentally safe, and relatively cheap, although science-intensive. Three substantial prerequisites exist that allow us to believe in the prospects for the development of new efficient biotechnologies for enhancing oil recovery based on the geochemical activity of microorganisms. First, oil fields exploited with water flooding are widely inhabited by aerobic and anaerobic microorganisms belonging to various physiological groups, which retain viability and biochemical activity in oil strata. Second, microorganisms are able to degrade oil hydrocarbons to smaller and more labile organic molecules and to synthesize such oil-releasing agents as ee 2 , ec 4 , fatty acids, alcohols, polysaccharides, surfactants, and other technologically active substances. Third, microorganisms are capable of in situ production of oil-releasing substances directly in zones and microzones containing residual oil. Present research that aims at the development of biotechnologies for oil recovery enhancement should be concerned with study of the regularities of microbial distribution and geochemical activity in oil fields under different geophysical conditions, as well as with advanced investigation of physiological and biochemical characteristics of microorganisms and development of methods for regulation of microbial processes in oil fields [3].