Oil fields are highly specific ecosystems - they contain no oxygen and the temperature, pressure and salinity are often high, which makes them home to a very particular community of bacteria.

Geert van der Kraan, a doctoral student who received his Ph.D. from TU Delft on the subject, says using bacterial changes as a biomonitoring tool in oil fields can be a way of keeping tabs on the state of the oil field itself - and increase its yield.

As oil recovery occurs, so do numerous changes in its ecosystem.   For example, in order to extract more oil from a field, methods such as pumping seawater used to flush oil out. Seawater injection has a number of effects, such as the introduction of sulphate. This changes the composition of the bacteria populations in the oil field. Bacteria that reduce sulphate thrive, prompting the release of hydrogen sulphide, which is not only toxic but also has an adverse effect on the quality of the oil and damages the pipelines.

Because of hydrogen sulphide concerns, these bacteria have always been closely monitored by the oil industry.  van der Kraan wanted to know whether the microbial changes (i.e. the types and quantity of bacteria present) could be used as an information source to track what is taking place in the oil field,  an approach that has the potential to boost oil exploitation or to prevent the production of harmful hydrogen sulphide at an early stage.  Smart management of oil wells. 

Geert van der Kraan studied various Dutch oil fields, focusing on the microbial communities living there. “There are very positive indications that biomonitoring is a realistic option. 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.”

In addition to monitoring, bacteria can also be used to improve oil extraction. Geert van der Kraan said, “Encouraging the growth of certain groups of bacteria at specific locations in the oil field is an interesting proposition. This growth 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." 

Geert van der Kraan is the first researcher to obtain his doctorate as part of the ISAPP programme (Integrated System Approach Petroleum Production). ISAPP is a collaboration between TU Delft, Shell International Exploration&Production and TNO.