Monitoring the ups and downs of bacterial populations in an oil field provides useful information for on the state of the oil field itself, and such biomonitoring could be applied to increase the yield from a field, according to research by Geert van der Kraan, at TU Delft.
Oil fields are highly specific ecosystems. They contain no oxygen and the temperature, pressure and salinity are often high, meaning fields are home to a very particular community of bacteria. The exploitation of oil fields gives rise to a great many changes in these bacterial populations.
One method of extracting extra oil from a field involves pumping in seawater to flush the oil through. This has a number of effects, including the introduction of sulphate. As a result, bacteria that metabolise sulphate thrive, prompting the release of hydrogen sulphide. This is not only toxic, but also has an adverse effect on the quality of the oil and damages the pipelines.
For this reason, these bacteria have always been closely monitored in the oil industry. van der Kraan investigated whether changes in the types and quantity of other bacteria present could be used to get a more comprehensive view of what was happening in an oil field. “The changes in the microbial diversity of the pore water from the oil well can provide a good understanding of the changing geochemical conditions in the oil field itself. This may well enable the oil field to be exploited more efficiently,” van der Kraan says.
Bacteria can also be used to improve oil extraction. “Encouraging the growth of certain groups of bacteria at specific locations in the oil field [...] partially blocks the porous structure of the rock that contains the oil, forcing the water to take another route. It can then move oil that is more difficult to reach, increasing the effectiveness of oil extraction,” said van der Kraan.
van der Kraan is the first researcher to obtain his doctorate as part of the ISAPP programme - Integrated System Approach to Petroleum Production - a collaboration between TU Delft, Shell International Exploration & Production and TNO.