A new method which simplifies drilling operations in unstable formations has been tested by Statoil on the Brage field. This “liner drilling” solution makes it possible to operate with a well liner attached directly to a steerable drillstring, and represents a global innovation. In conventional drilling, work has to halt while the string is pulled from the well and a liner set to prevent the borehole walls from collapsing. “Setting liner while drilling means we don’t have to leave the borehole open and minimises the risk of collapse,” explained Geir Slora, head of drilling and well at Statoil. In order to enhance the profitability of mature fields, Statoil is constantly working to improve their recovery factor. Liner drilling can contribute to these efforts.