The design of oil wells in the Danish North Sea presents significant challenges to structural integrity and utilisation of the well. These wells are up to 10 km long horizontally, making access to the far end for ongoing maintenance extremely difficult.
The research in this programme takes place in two independent themes: Improved cement and Extended reach with coiled tubing. They both contribute to maintaining the efficiency of Danish oil production, which stands out as being some of the most energy efficient in the world.
When drilling wells, cement is used to insulate and support production pipes, and when this cement solidifies, it cracks. We are developing a cement that can repair these cracks itself, by embedding a bacterial culture into the cement that forms calcium carbonate, or limestone where the cracks occur.
Very few living organisms can survive the extreme acidity, salt, pressure and temperature conditions that the cement offers, and at the same time the bacteria must have sufficient nutrition to survive. Therefore, we have tackled a major challenge by identifying and isolating promising bacteria that we are testing for commercial use.
Extended reach with coiled tubing
At the same time, we are developing methods to reach the end of the very long horizontal wells. With the current technology we can only reach approx. half way out with coiled tubing, a hollow metal tube used for maintenance tasks, which means it will be difficult to solve problems with scaling and water production in the outer parts of the well. We are therefore working to develop a substance that can reduce friction as the operator pushes coiled tubing down through the well. Our mathematical models indicate that a reduction in friction with the right substance will allow access to depths not previously possible.
Our research becomes a reality through collaboration of different disciplines and expertise. A good example is the work on self-healing cement, where researchers with a high knowledge of bacteria collaborate with researchers who have a great deal of knowledge about cement, and with other researchers who have a great knowledge of how to test cement. Only by combining expertise in this way do we achieve results that can make a difference in production.