Abstract: A method to be used when performing drilling in a well bore and a device for performing the method are disclosed. The method includes positioning in the well bore a drill string comprising at least two pipe conduits, an upper end, and a lower end comprising a drilling tool, thereby forming an outer annulus between the well bore wall and the drill string. A well bore section comprising at least one u-shaped section is drilled. A first fluid with a first density is fed into the outer annulus above the u-shaped section, and a second fluid with a second density is provided within the drill string and around the tool, where the first density is larger than the second density.

Abstract: A method and device for drilling or cleaning an underground borehole. The device includes a drilling tool, a drill string with two pipe conduits extending up to the surface and an arrangement for providing one drilling fluid for circulation in a drill string and a second arrangement for providing a second fluid in an annulus formed between the drill string and the wall of a borehole making the drill string approximately weightless.

Abstract: A method to be used when performing drilling in a well bore and a device for performing the method are disclosed. The method includes positioning in the well bore a drill string comprising at least two pipe conduits, an upper end, and a lower end comprising a drilling tool, thereby forming an outer annulus between the well bore wall and the drill string. A well bore section comprising at least one u-shaped section is drilled. A first fluid with a first density is fed into the outer annulus above the u-shaped section, and a second fluid with a second density is provided within the drill string and around the tool, where the first density is larger than the second density.

Abstract: A method and device for a running tool for drilling or cleaning and setting a lining and a completion string in an underground borehole. The running tool comprising a drilling tool, an expandable casing, an expansion tool, a packer arranged to seal against the wall of the casing, and at least one conduit extending up to the surface. The drilling tool is releasably connected to the lower portion of the expanding casing, and the expansion tool and the packer are releasably connected to the upper portion of the expanding casing. The running tool is arranged to communicate with the surface through at least one pipe conduit.

Abstract: A method and a device for establishing an underground borehole (10) and setting a casing (6) in the borehole (10), wherein the running tool (1) including a drilling tool (14), an expandable casing (6), an expansion tool (32) and a packer (30) which is arranged to seal against the wall of the borehole (10), is placed at the bottom of the borehole (10), whereupon the borehole (10) is drilled to the necessary length in order then to set the expandable casing (6), and in subsequent operations the casing is reinforced and a completion string is run, having built-in cables for downhole control and monitoring.

Abstract: A method and device for drilling or cleaning in underground borehole including a drilling tool, a drill pipe with two pipe conduits extending up the surface and further including an arrangement for providing one drilling fluid for circulation with a drill string and a second arrangement for providing a second fluid in an annulus formed between the drill string and the wall of a wellbore.

Abstract: A method and device for a running tool for drilling or cleaning and setting a lining and a completion string in an underground borehole, The running tool comprising a drilling tool, an expandable casing, an expansion tool, a packer arranged to seal against the wall of the borehole, and at least one conduit extending up to the surface. The drilling tool is releasably connected to the lower portion of the expanding casing, and the expansion tool and the packer are releasably connected to the upper portion of the expanding casing. The running tool is arranged to communicate with the surface through at least one pipe conduit.