I. A. Borzenkov

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

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].

Occurrence and geochemical activity of microorganisms in high‐temperature, water‐flooded oil fields of Kazakhstan and Western Siberia

The distribution of different methanogenic and sulfate‐reducing bacteria and their activity in formation waters of Uzen, Mykhpay, and Talinskoe oil fields, characterized by temperatures of the strata of 50–70°C and higher, were investigated. Injection of surface waters was shown to result in development of biogenic oil transformation. The temperature of injected waters determined the temperature regime and the presence of either mesophilic or thermophilic microorganisms in the microbial community near the bottom zone of injection wells. The number and activity of thermophilic microorganisms in the zone of producing wells were low or absent. Despite the absence of oxygen in the injected water, active microbiological processes occurred in the water‐flooded oil fields. We concluded that the development of biogenic processes in oil fields proceeded not only as an aerobic‐anaerobic microbiological succession but also as anaerobic transformation of organic matter injected with the surface water and of component...

The new facultatively chemolithoautotrophic, moderately halophilic, sulfate-reducing bacterium Desulfovermiculus halophilus gen. nov., sp. nov., Isolated from an oil field

The new mesophilic, chemolithoautotrophic, moderately halophilic, sulfate-reducing bacterium strain 11-6, could grow at a NaCl concentration in the medium of 30–230 g/l, with an optimum at 80–100 g/l. Cells were vibrios motile at the early stages of growth. Lactate, pyruvate, malate, fumarate, succinate, propionate, butyrate, crotonate, ethanol, alanine, formate, and H2/CO2 were used in sulfate reduction. Butyrate was degraded completely, without acetate accumulation. In butyrate-grown cells, a high activity of CO dehydrogenase was detected. Additional growth factors were not required. Autotrophic growth occurred, in the presence of sulfate, on H2/CO2 or formate without other electron donors. Fermentation of pyruvate and fumarate was possible in the absence of sulfate. Apart from sulfate, sulfite, thiosulfate, and elemental sulfur were able to serve as electron acceptors. The optimal growth temperature was 37°C; the optimum pH was 7.2. Desulfoviridin was not detected. Menaquinone MK-7 was present. The DNA G+C content was 55.2 mol %. Phylogenetically, the bacterium represented a separate branch within the cluster formed by representatives of the family Desulfohalobiaceae in the class Deltaproteobacteria. The bacterium was assigned to a new genus and species, Desulfovermiculus halophilus gen. nov., sp. nov. The type strain is 11-6T (= VKM B-2364), isolated from the highly mineralized formation water of an oil field.

[The properties of hydrocarbon-oxidizing bacteria isolated from the oilfields of Tatarstan, Western Siberia, and Vietnam].

Eleven strains of hydrocarbon-oxidizing bacteria, isolated from oilfields and representing the genera Rhodococcus, Gordonia, Dietzia, and Pseudomonas, were characterized as mesophiles and neutrophiles. Rhodococci were halotolerant microorganisms growing in a media containing up to 15% NaCl. All the strains oxidized n-alkanes of crude oil. An influence of the cultivation temperatures (28 or 45°C) and organic supplements on the degradation of C12-C30n-alkanes in oxidized oil by two bacterial strains of the genus Pseudomonas was shown. The introduction of acetate, propionate, butyrate, ethanol, and sucrose led mainly to decreased oxidation of petroleum paraffins. At certain cultivation temperatures, the addition of volatile fatty acid salts increased the content of certain n-alkanes in oxidized oil as compared to crude oil.

[Microbiological processes in a high-temperature oil field].

Thermophilic sulfate-reducing bacteria (SRB) oxidizing lactate, butyrate, and C12–C16n-alkanes of oil at a temperature of 90°C were isolated from samples of water and oil originating from oil reservoirs of the White Tiger high-temperature oil field (Vietnam). At the same time, no thermophiles were detected in the injected seawater, which contained mesophilic microorganisms and was the site of low-temperature processes of sulfate reduction and methanogenesis. Thermophilic SRB were also found in samples of liquid taken from various engineering reservoirs used for oil storage, treatment, and transportation. These samples also contained mesophilic SRB, methanogens, aerobic oil-oxidizing bacteria, and heterotrophs. Rates of bacterial production of hydrogen sulfide varied from 0.11 to 2069.63 at 30°C and from 1.18 to 173.86 at 70°C μg S/(l day); and those of methane production, varied from 58.4 to 100 629.8 nl CH4/(l day) (at 30°C). The sulfur isotopic compositions of sulfates contained in reservoir waters and of hydrogen sulfide of the accompanying gas indicate that bacterial sulfate reduction might be effective in the depth of the oil field.

Additional Oil Production During Field Trials in Russia

Abstract In field experiments, we tested an original technology to enhance oil recovery based on the activation of the stratal microflora of flooded oil fields. The technology includes the injection of aerated fresh water with added mineral salts. The activity of microflora (aerobic and anaerobic) increased sharply in the near-bottom zone of the injection well. The microbiological processes occurred in two stages. The first stage includes the activation of aerobic oxidation of organic matter in the oil, which leads to the formation of oil displacement agents, such as organic acids, surfactants, polysaccharides, and carbonic acid. During the second, anaerobic stage gases, methane, and carbonic acid were formed. The field tests were carried out in three pilot tests of different waterflooded areas of the Romashkino field. The additional oil that was recovered reached a total of 41.08 t.t, that was 32.9% of the total pilot production. The enhancement of oil recovery correlated with the rate of methanogenesis. The carbon isotope composition of the carbonates of stratal waters and the concentration of one of the main degradation products (acetate) were changed.

A microbiological study of an underground gas storage in the process of gas extraction

The liquid phase of different units of an underground gas storage (UGS) in the period of gas injection was studied with respect to its hydrochemical composition and characterized microbiologically. The presence of viable aerobic and anaerobic bacteria was revealed in the UGS stratal and associated waters. An important source of microorganisms and biogenic elements in the ecosystem studied is water and various technogenic admixtures contained in trace amounts in the gas entering from the gas main in the period of gas injection into the storage. Owing to this fact, the bacterial functional diversity, number, and activity are maximal in the system of gas treatment and purification and considerably lower in the observation well zone. At the terminal stages, the anaerobic transformation of organic matter in the UGS aqueous media occurs via sulfate reduction and methanogenesis; exceptionally high rates of these processes (up to 4.9 × 105 ng S2− l−1 day−1 and 2.8 × 106 nl CH4 l−1 day−1, respectively) were recorded for above-ground technological equipment.

Dynamics of Microbial Processes in the Stratal Waters of the Romashkinskoe Oil Field

The dynamics of the microbial processes developing in parallel with the exploitation of the Romashkinskoe oil field (Tatarstan) were studied in two areas differing in the degree of stratal water freshening. Flooding of the strata, in conjunction with purposeful measures on stratal microflora activation, was shown to increase the microbial population density and activate both methanogenesis and sulfate reduction; the latter process was limited by the low sulfate concentration. Development of anaerobic processes correlated with changes in acetate concentration in the stratal water. High mineralization (over 200 g/l) inhibited the stratal water microflora even if other conditions were favorable. Isotopic analysis of the carbonate carbon showed that the bicarbonate concentration increased in the stratal water due to microbial degradation of oil hydrocarbons and further participation of the biogenic carbon dioxide in dissolution of the carbonate cement of the oil-bearing strata. In strongly desalinated stratal water, the proportion of the newly formed bicarbonate was as high as 80%.

Halotolerant and Extremely Halophilic Oil-Oxidizing Bacteria in Oil Fields

Abstract Field experiments have shown that oil-oxidizing microflora are widely distributed in the oil fields of Russia. Oil-oxidizing microorganisms were isolated from stratal waters with salinities of up to 272 g/l. Only single oil-oxidizing microbial cells were found in the stratal waters of production wells. High salinity stratal waters (with salinity over 140 g/l) are characterized by “oil-positive” microflora that are concentrated in the oil. Oil-oxidizing eubacteria, active in media with salinities up to 15% NaCl, and the extremely halophilic oil-oxidizing archaeobacteria, active at salinites to 32% NaCl, were isolated from oil samples of the Bondyuzhskoye oil-field. These microorganisms were characterized by high oil-emulsifying activity. Some properties of the halophilic oil-oxidizing microorganisms are discussed.

Isolation and investigation of anaerobic microorganisms involved in methanol transformation in an underground gas storage facility

High methanol and acetate concentrations (up to 12 and 14 g l−1, respectively) were found in water samples collected at different objects of the North Stavropol underground gas storage facility (UGSF), and significant seasonal variations in the content of these compounds were revealed. The dominant anaerobic microorganisms isolated from these samples during the study belonged to acetogens, methanogens, and sulfate reducers. The results of 16S rRNA gene sequencing and analysis of the physiological properties showed that the isolates were close to the species of Eubacterium limosum, Sporomusa sphaeroides, Methanosarcina barkeri, Methanobacterium formicicum, and Desulfovibrio desulfuricans. The isolated organisms, except for Methanobacterium formicicum, were capable of methylotrophic growth. All strains were characterized by resistance to high methanol concentrations (up to 40–50 g l−1). Their other energy substrate was hydrogen. The combination of the growth characteristics of these strains (pH, temperature, and salinity ranges) was shown to correspond to the ecological situation observed in the UGSF. The results of investigation of the isolated strains suggest that organic acids (acetate, butyrate) found in high concentrations in the initial samples are metabolic products of the revealed acetogens. Based on the established biological peculiarities of the isolated strains of methanogens, acetogens, and sulfate-reducing bacteria, these microorganisms may be considered as the main agents of anaerobic transformation of methanol and some other organic and inorganic compounds in UGSFs.