Modifies the water for more oil with less CO2 emissions

The Norwegian continental shelf is getting older, and most of the old fields produce significant amounts of water. To get the maximum amount of oil out of the reservoir, large amounts of water are pumped in under the oil reservoir itself, so-called water injection. The increased water volume pushes the oil ahead and helps to maintain reservoir pressure so that oil production is maintained.

A reservoir usually consists of three main zones. At the top there is gas, then a layer of oil and below this we find water. This water is called formation water.

As of today, we do not get all the oil out when injecting water into oil reservoirs. Significant assets are therefore left undeveloped. The reason is that the water does not enter the entire reservoir and part of the oil will remain in pores in the rocks.

Heavier water gives more recovery

– Among other things, we work on adding chemicals to the water, so that it becomes heavier. This can be, for example, polymers, silicates or gels. Heavier water comes in contact with a larger area of the reservoir where the oil is found. By using this method we will recover much more of the oil found in the reservoir, says John Zuta, head of research at NORCE.

Some of the oil reservoirs in the North Sea may be water-wet and others are less water-wet. This means that in some reservoirs the water seeps into the rocks, and in other places it remains on the outside.

At Ullandhaug in Stavanger, we have an advanced underground current laboratory. The laboratory is used to test new technology before it is implemented in the oil and gas fields on the Norwegian continental shelf.

The more water that is injected into the reservoir, the higher the CO2 emissions will be. More and more water will also be required, as the field becomes older.

- At Ekofisk, for example, almost nine barrels of water are injected to produce one barrel of oil. This costs a lot and produces a lot of emissions, says Zuta.

Changes the seawater from Ekofisk

Now the researchers are working with Ekofisk and testing whether they can do something with the seawater to recover more of the oil that remains in the reservoir.

– We will change the chemical composition of the seawater we have received from Ekofisk field, and then pump it down to the formation water. When this mixes, a chemical reaction occurs which means that we can recover more of the oil sitting in the pores of the rocks, says Zuta.

Requires different methods

The oil and gas reservoirs are very different. There are different temperatures, pressures, and rocks. It is important to understand the type of reservoir you are working with as different types of reservoirs require different types of oil extraction methods.

– We test what happens with various parameters such as pressure temperature and water composition. In the lab, we have everything on a small scale, but with software, we simulate what happens when this is scaled up. We do all this in close cooperation with the users, and the aim is to give them as much information as possible to be able to scale up, says Zuta.

The researchers have also calculated the cost of water injection and how much CO2 emissions water injection gives. They will find out if it is possible to produce oil in a different way - with less water injection and with less CO2 emissions.

Using the underground in the future

We already know that by injecting CO2 together with the water, we get more oil produced. Increased oil extraction is the aim in the first instance, but we can also use this expertise for CO2 storage. Storing CO2 in connection with increasing oil extraction can bring benefits, both financially and for the environment.

– Our lab can be used to gain more knowledge about how we can use the underground for something else, for example, CO2 storage and geothermal energy, says Zuta.

Lab at Ullandhaug

In our laboratory at Ullandhaug, we offer experimental research related to improved oil recovery, increased oil recovery, CO2 utilization and storage, and special core analyses.

The laboratory facilities are typically used in projects within the oil and gas industry, service companies, chemical suppliers, and the Research Council of Norway. The equipment is flexible, scalable, and can be adapted to the customers' various needs. Several of the central laboratory facilities have been developed through collaboration with the petroleum and service industry.