Abstract: A method for drilling boreholes using casing as the drill string and for removing a drilling assembly from the wellbore while leaving the casing in the well bore. In the method, the drilling assembly is prepared for removal from the wellbore by launching a release tool and manipulating the drilling assembly using the release tool.

Abstract: A method for drilling boreholes using casing as the drill string and for removing a drilling assembly from the wellbore while leaving the casing in the well bore. In the method, the drilling assembly is prepared for removal from the wellbore by launching a release tool and manipulating the drilling assembly using the release tool.

Abstract: A method for drilling with a liner includes: providing a liner string including an upper portion extending towards surface and a lower portion; drilling to a depth with the liner string; disconnecting the upper portion from the lower portion; pulling the upper portion from the well; and leaving the lower portion in the well to line the wellbore. A drilling assembly for drilling a borehole with a borehole liner includes: an upper liner string; a lower liner string including an upper end and a lower end; a releasable connector connecting the lower liner string to the upper liner string; and a drilling assembly connectable at the lower end of the lower liner string.

Abstract: A wear resistant casing connection including a wear resistant portion on its exterior surface is taught. A casing connection having a controlled bend angle is also taught.

Abstract: A method for drilling and cementing a borehole to access at least a portion of a formation of interest, comprising: drilling a borehole using a drill string including an external packer and a drilling assembly to access at least a portion of a formation of interest; using a drilling fluid selected to minimize adverse effects on the at least a portion of the formation of interest when drilling into the at least a portion of the formation of interest; setting the packer to create a seal in the borehole so that (i) an upper drill string/borehole annulus above the packer is isolated from (ii) a lower drill string/borehole annulus below the packer, with the at least a portion of the formation of interest being open to the lower drill string/borehole annulus; and introducing cement above the external packer into the upper drill string/borehole annulus.

Abstract: A process for retrieving a bottom hole assembly through a casing string may include: installing a casing string in a borehole, the casing string including a bottom hole assembly releasably engaged thereto and moveable through an inner diameter of the casing string; releasing the bottom hole assembly from engagement with the casing string; reducing hydrostatic pressure in the casing string inner diameter above the bottom hole assembly so that the casing string inner diameter pressure above the bottom hole assembly is lower than a fluid pressure below the bottom hole assembly; permitting reverse circulation down through an annulus between the casing string and the borehole to permit the bottom hole assembly to rise up through the casing string toward the surface; and retrieving the bottom hole assembly from the casing string.

Abstract: A method for drilling boreholes using casing as the drill string and for removing a drilling assembly from the wellbore while leaving the casing in the well bore. In the method, the drilling assembly is prepared for removal from the wellbore by launching a release tool and manipulating the drilling assembly using the release tool.

Abstract: A valve (30), a drill string valve assembly (10) and a method of drilling using compressed fluid as a drill drilling fluid are described. The valve and valve assembly (10) may be used in order to prevent escape of compressed fluid during the time that a connection is being made into the drill string. The valve (10) can be insertable into a drill string inner diameter to seal against fluid passage past the body except through the valve (30) and can be selected to maintain fluid pressure in the drill string when the upper end of the drill string is open to atmosphere. The valve can also be capable of being releasably engaged to a drive mechanism, such as a top drive (40) which is handling the drill string (12) to be slidably moved within the drill string, as driven by the drive mechanism, but releasable from the drive mechanism, when the drive mechanism is removed from the drill string.

Abstract: A wear resistant casing connection including a wear resistant portion on its exterior surface is taught. A casing connection having a controlled bend angle is also taught.