Small bacteria – big money
They are tiny, and they eat oil. Still, they are the ones that can help us obtain more underwater black gold. Oil-eating bacteria will be used to detect oil that cannot be recovered by other methods and make the route out of reservoirs smoother. The method is called ‘Microbial Improved Oil Recovery’ shortened to MIOR.
Researchers at Norwegian University of Science and Technology (NTNU) have made comprehensive studies of the MIOR method and have tested the effect of different varieties on the level of oil recovery.
– The winner of the tests is the Non-Surfactant Producing Bacteria, says Research Fellow Christian Crescente. It increased oil recovery by 4.2 per cent. The most important kind of testing is still to discover how these mechanisms can lead to an increase in oil recovery using bacteria.
If we understand what is happening, we can make plans and have fewer surprises when we start using bacteria in real reservoirs. We have to remember that surprises are expensive in the oil business. On the other hand one per cent higher oil recovery from Norwegian operative oil fields represents an estimated gross value of 300 billion Norwegian kroner.
Changing the drainage
The process of recovering oil requires a lot more than a long straw down to the bottom of the sea. The oil deposits are in porous rock. When the reservoir is initially breached, the oil will come out almost by itself, just like puncturing a balloon filled with water. As pressure in the reservoirs falls, the oil has to be assisted usually by water that is being pumped into the reservoir.
– Just as rivers find their way through the landscape, water will find its way through the reservoir. This means that oil that is beyond the well drainage will not surface from the reservoir, says Christian Crescente.
This is where the bacteria appear.
– We imagine that will they change the reservoir drainage and find their way to oil that was unrecoverable before, says the scientist.
Making drops slippery
This is only one of the effects oil-eating bacteria may have. Even though we normally think of oil in large barrels, it originally consists of numerous tiny drops in water-filled rock. The drops are so tiny that it is difficult to rinse them out with water.
– The tension in the surface of the oil drops causes them to be caught up in the pores of the rock like a blown-up balloon in a net, explains Christian Crescente, at the Department of Petroleum Engineering and Applied Geophysics, NTNU.
– But, when the bacteria eat some of the surface of the oil drops and this makes them more buoyant, just like soaping a balloon so that it could slip through the net mesh.
Bacteria also change the pore wall of the reservoir, and this makes it easier for the oil to flow through. In addition gases are created, which cause increased pressure in the reservoir, and this again makes it easier for the oil surface.
– A chain of chemical reactions occurs, which contribute to make the reservoir more slippery, explains Christian Crescente. This means that there will be more oil coming up.
Right kind, right method
There are already some types of bacteria in a reservoir, but bacteria can also be inserted and be successfully cultivated. It is important to do research on the specific bacteria that are going to be used in these reservoirs. Oil exists in different kinds of rock which need different kinds of bacteria.
It is all about cultivating the right kind of bacteria and in the right amount. The reservoir functions as its own ecosystem, and if the supply of nutrient is controlled the bacteria will multiply in number and speed.
Compared to other methods of oil recovery MIOR has plenty of advantages. It is cheaper than other methods. It can be used in most kinds of reservoirs. The chemicals that are needed can be made on the spot; in the reservoirs, and chemicals that can be added are cheap and easily available. The method requires minimal extra logistics and is therefore easy to use offshore.
Cheap, but difficult
The method has been in use in many parts of the world, with mixed experience. Lacking both knowledge and planning has barred the good results. Although the method is cheap it is also difficult. Knowledge about how the different types of bacteria function inside the various kinds of rocks that contain oil is the key to obtain a good degree of oil recovery.
– In the Norwegian sector Statoil Hydro has a MIOR project in the Norne fields. Nothing is published about it, so I do not know anything about the results, says Christian Crescente, – but this is an ongoing project, and I assume they have come up with some interesting data.
The goal is 70 per cent
The focus on technology improvements in the Norwegian sector has caused a yearly increase in the percentage of oil recovery. Early in the 1990s one estimated that 35 per cent oil recovery was possible, but it is 46 per cent today. The goal is that the oil recovery rate is to increase even more in the years to get and come close to 70 per cent.
By Hege J. Tunstad/The Reseach Magazine Gemini
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