Abstract: A method of providing a downhole seal, such as a packer, in a drilled bore between inner tubing and outer tubing comprises: providing an intermediate tubing section defining a seal arrangement for engaging with the inner tubing; and radially plastically deforming the intermediate tubing section downhole to form an annular extension. The extension creates a sealing contact with the outer tubing.

Abstract: A downhole filter comprises a tubular member having a wall defining a plurality of openings. The openings have an outer width less than an inner width. The parts of the opening defining the smaller width are defined by radially outer parts of the openings, such that particulates or sand prevented from passing through the openings will tend to be retained to the outside of the tubular member.

Abstract: Apparatus (10) for facilitating coupling and cementing of downhole tubulars (12, 28) comprises a tubing section (12, 10) for use in lining a bore. The tubing section has upper and lower ends and defines a tubing wall having cement outlets (20) spaced from the lower end of the tubing. The lower end of the tubing is selectively closed, and swab cups (22) are provided externally of the lower end of the tubing below the cement outlets (20) for restricting passage of cement.

Abstract: A method and apparatus is provided for drilling and lining a wellbore in one downhole trip. The method comprises mounting a drill bit on a drill string including a section of expandable tubing and providing a tubing expander in the string, then rotating the drill bit and advancing the drill string through a bore, then passing the expander through the expandable tubing to expand the tubing, wherein the expandable tubing is deformed by compressive plastic deformation of the tubing with a localised reduction in wall thickness, resulting in a subsequent increase in tubing diameter, and then retrieving the drill bit from the bore through the expanded tubing.

Abstract: A method of installing a liner in a drilled bore below a section of bore previously lined with casing comprises the steps of: running a length of liner into the bore such that at least an upper end of the liner is positioned in overlapping relation with at least a lower end of the casing; and plastically deforming a portion of the liner such that an external face of the portion forms an interference fit with an internal face of a portion of the casing. The interference fit preferably provides both hanging support for the liner and a fluid-tight seal between the liner and casing.

Abstract: Apparatus (10) for facilitating coupling and cementing of downhole tubulars (12, 28) comprises a tubing section (12, 10) for use in lining a bore. The tubing section has upper and lower ends and defines a tubing wall having cement outlets (20) spaced from the lower end of the tubing. The lower end of the tubing is selectively closed, and swab cups (22) are provided externally of the lower end of the tubing below the cement outlets (20) for restricting passage of cement.

Abstract: A tubing connection arrangement (10) comprises two expandable tubing sections (12, 14), each tubing section comprising a filter screen (16, 18) sandwiched between inner expandable tubing (20, 22) and outer expandable tubing (24, 26). The filter screen of one tubing section overlaps the filter screen of the other tubing section and the outer expandable tubing of at least one of the tubing sections extends over the overlapping filter screens. On expansion of the tubing sections, the overlapping filter screens, restrained by the outer tubing, ensure the integrity of the filter between the tubing sections.

Abstract: A method of increasing the collapse resistance of a tubular comprises locating a tool having at least one, and typically three, bearing members within a tubular. The bearing members are positioned in engagement with a wall of the tubular to apply a radial force to a discrete zone of the wall. This radial force is then applied to further discrete zones of the wall, the level of radial force being selected such that the collapse resistance of the tubular is increased.

Abstract: A downhole apparatus comprises a plurality of tubing sections. Each tubing section has substantially cylindrical portions initially of a first diameter for coupling to end portions of adjacent tubing sections. The end portions are expandable to a larger second diameter. Each tubing section also has an intermediate folded wall portions initially in a folded configuration. The intermediate folded wall portions are unfoldable to define a substantially cylindrical form of a third diameter.

Abstract: A method of installing a liner in a drilled bore below a section of bore previously lined with casing comprises the steps of: running a length of liner into the bore such that at least an upper end of the liner is positioned in overlapping relation with at least a lower end of the casing; and plastically deforming a portion of the liner such that an external face of the portion forms an interference fit with an internal face of a portion of the casing.

Abstract: A method of providing a downhole seal, such as a packer, in a drilled bore between inner tubing and outer tubing comprises: providing an intermediate tubing section defining a seal arrangement for engaging with the inner tubing; and radially plastically deforming the intermediate tubing section downhole to form an annular extension. The extension creates a sealing contact with the outer tubing.

Abstract: An expandable coupling arrangement for coupling first and second tubulars includes a male thread portion on an end of the first tubular and a female thread portion on an end of the second tubular. The thread portions comprise dovetail threads having flanks, roots and crests, wherein the flanks are inclined at an angle of greater than 10°.

Abstract: A method of isolating a section of downhole tubing comprises: running a length of expandable tubing (20) into a tubing-lined borehole (12, 14) and positioning the expandable tubing (20) across a section of tubing to be isolated; deforming at least portions of the expandable tubing (36, 40) to increase the diameter of the portions to sealingly engage the tubing (14) and to isolate the tubing section.

Abstract: A method and apparatus is provided for drilling and lining a wellbore in one downhole trip. The method comprises mounting a drill bit on a drill string including a section of expandable tubing and providing a tubing expander in the string, then rotating the drill bit and advancing the drill string through a bore, then passing the expander through the expandable tubing to expand the tubing, wherein the expandable tubing is deformed by compressive plastic deformation of the tubing with a localised reduction in wall thickness, resulting in a subsequent increase in tubing diameter, and then retrieving the drill bit from the bore through the expanded tubing.

Abstract: A method of lining a drilled bore comprises running an expandable first tubular into a bore and locating part portion of the first tubular in an unlined section of the bore and another portion of the first tubular overlapping a portion of an existing second tubular. The first tubular is secured relative to the second tubular while retaining the provision of fluid outlets to permit displacement of fluid from an annulus between the first tubular and the bore wall. An expansion device is then run through the first tubular to expand the first tubular to a larger diameter. Cement is then circulated into the annulus between the expanded first tubular and the bore wall. The fluid outlets are then closed.

Abstract: Apparatus (10) for facilitating coupling and cementing of downhole tubulars (12, 28) comprises a tubing section (12, 10) for use in lining a bore. The tubing section has upper and lower ends and defines a tubing wall having cement outlets (20) spaced from the lower end of the tubing. The lower end of the tubing is selectively closed, and swab cups (22) are provided externally of the lower end of the tubing below the cement outlets (20) for restricting passage of cement.

Abstract: A method and apparatus is provided for drilling and lining a wellbore in one downhole trip. The method comprises mounting a drill bit on a drill string including a section of expandable tubing and providing a tubing expander in the string, then rotating the drill bit and advancing the drill string through a bore, then passing the expander through the expandable tubing to expand the tubing, wherein the expandable tubing is deformed by compressive plastic deformation of the tubing with a localised reduction in wall thickness, resulting in a subsequent increase in tubing diameter, and then retrieving the drill bit from the bore through the expanded tubing.

Abstract: A method of isolating a section of downhole tubing comprises: running a length of expandable tubing (20) into a tubing-lined borehole (12, 14) and positioning the expandable tubing (20) across a section of tubing to be isolated; deforming at least portions of the expandable tubing (36, 40) to increase the diameter of the portions to sealingly engage the tubing (14) and to isolate the tubing section.

Abstract: Expandable tubing (20) has a tubing wall (22) comprising a plurality of deformable tubular structures (24). The structures (24) have permeable walls and containing a filter medium (28) such that fluid may flow through the structures (24) and the filter medium (28) and thus through the tubing wall (22).

Abstract: A method of providing a downhole seal, such as a packer, in a drilled bore between inner tubing and outer tubing comprises: providing an intermediate tubing section defining a seal arrangement for engaging with the inner tubing; and radially plastically deforming the intermediate tubing section downhole to form an annular extension. The extension creates a sealing contact with the outer tubing.