Publicação
Development of efficient microbial enhanced oil recovery processes at high pressure
| Resumo: | Crude oil is expected to remain the main source of energy in the near future. Under these circumstances, and considering the decrease of oil reserves, it is necessary to explore mature reservoirs to ensure the growing oil demand. Current technologies recover only 30 to 50% of the oil present in the reservoirs. Microbial enhanced oil recovery (MEOR) uses microorganisms and their metabolites, to recover the entrapped oil, and it is expected that this technology can increase oil recovery by 30%. In this study, Bacillus subtilis #573 isolated from a Brazilian oil well with a temperature of 40°C and a pressure of 32.4 bar was studied for its applicability in MEOR. The aim of this work was to study the potential of this isolate for MEOR applications under the reservoir conditions, namely under high pressures. For this purpose, five different methods were used, namely the culture in serum bottles, shaken flasks, non-pressurized bioreactor and in pressurized reactor, and finally in sand-pack columns. This allowed the study of the growth and production of biosurfactants under atmospheric pressure and under high pressures. The results showed that the isolate was able to grow and produce biosurfactants (reducing the surface tension up to 26 mN/m) under aerobic conditions, oxygen-limiting conditions, and pressures and temperature up to 47bar and 50°C, respectively. The biosurfactants produced in the different conditions were extracted, purified and characterized, being constituted by different surfactin isoforms (C12, C13, C14, C15 and C16). Furthermore, the expression of the gene srfA involved in the synthesis of surfactin) was studied in order to assess the impact of high pressure in its expression: The results obtained suggest a higher relative expression at high pressure. Biosurfactant production was studied at different temperatures and pressures, and it was concluded that this isolate presents a high versatility with respect to the range of temperatures and pressures in which biosurfactant is observed. Under 37°C and 46 bar it was possible to obtain a positive additional oil recovery of 14.5% in a sand-pack column assay. In conclusion, B. subtilis #573 is a potential candidate for use in advanced oil recovery processes under the high pressures studied. |
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| Autores principais: | Meneses, Cláudio Cerqueira |
| Assunto: | Ciências Agrárias Ciências Médicas Engenharia e Tecnologia Engenharia e Tecnologia |
| Ano: | 2018 |
| País: | Portugal |
| Tipo de documento: | dissertação de mestrado |
| Tipo de acesso: | acesso aberto |
| Instituição associada: | Universidade do Minho |
| Idioma: | inglês |
| Origem: | RepositóriUM - Universidade do Minho |
| Resumo: | Crude oil is expected to remain the main source of energy in the near future. Under these circumstances, and considering the decrease of oil reserves, it is necessary to explore mature reservoirs to ensure the growing oil demand. Current technologies recover only 30 to 50% of the oil present in the reservoirs. Microbial enhanced oil recovery (MEOR) uses microorganisms and their metabolites, to recover the entrapped oil, and it is expected that this technology can increase oil recovery by 30%. In this study, Bacillus subtilis #573 isolated from a Brazilian oil well with a temperature of 40°C and a pressure of 32.4 bar was studied for its applicability in MEOR. The aim of this work was to study the potential of this isolate for MEOR applications under the reservoir conditions, namely under high pressures. For this purpose, five different methods were used, namely the culture in serum bottles, shaken flasks, non-pressurized bioreactor and in pressurized reactor, and finally in sand-pack columns. This allowed the study of the growth and production of biosurfactants under atmospheric pressure and under high pressures. The results showed that the isolate was able to grow and produce biosurfactants (reducing the surface tension up to 26 mN/m) under aerobic conditions, oxygen-limiting conditions, and pressures and temperature up to 47bar and 50°C, respectively. The biosurfactants produced in the different conditions were extracted, purified and characterized, being constituted by different surfactin isoforms (C12, C13, C14, C15 and C16). Furthermore, the expression of the gene srfA involved in the synthesis of surfactin) was studied in order to assess the impact of high pressure in its expression: The results obtained suggest a higher relative expression at high pressure. Biosurfactant production was studied at different temperatures and pressures, and it was concluded that this isolate presents a high versatility with respect to the range of temperatures and pressures in which biosurfactant is observed. Under 37°C and 46 bar it was possible to obtain a positive additional oil recovery of 14.5% in a sand-pack column assay. In conclusion, B. subtilis #573 is a potential candidate for use in advanced oil recovery processes under the high pressures studied. |
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