The present invention describes a drill pipe in which various sections of the pipe are strengthened, or their shape is altered, in order to improve the wear and buckle resistance of the drill pipe; or in which various damaged sections of the pipe are repaired in order to maintain or improve the wear and buckle resistance of the drill pipe. In either case, the sections are strengthened using various hardening methods such as heat treatment processes and/or expansion techniques. A sleeve can also be applied to the strengthened portions. Surface enhancers, such as hardbanding, can be applied to the strengthened portions or the sleeve in order to provide abrasion resistance or to reduce friction.

A downhole apparatus, for example a centraliser, comprises a swellable material which expands upon contact with at least one predetermined fluid. In a first aspect of the invention, a centraliser comprises a body and a plurality of formations upstanding from the body. In another aspect, a downhole apparatus comprise a throughbore configured to receive a tubular, a swellable member, and a rigid assembly integrally formed with the swellable member. The rigid assembly provides stand off to the apparatus in use. In a further aspect, the downhole apparatus has a first condition, before expansion of the swellable member in which a rigid assembly defines a maximum outer diameter of the apparatus. In a second condition after expansion of the swellable member, the swellable member defines a maximum outer diameter of the apparatus. In a preferred embodiment the rigid assembly is designed to flex or deform under an axial or radial load.

A downhole apparatus, for example a centraliser, comprises a swellable material which expands upon contact with at least one predetermined fluid. In a first aspect of the invention, a centraliser comprises a body and a plurality of formations upstanding from the body. In another aspect, a downhole apparatus comprise a throughbore configured to receive a tubular, a swellable member, and a rigid assembly integrally formed with the swellable member. The rigid assembly provides stand off to the apparatus in use. In a further aspect, the downhole apparatus has a first condition, before expansion of the swellable member in which a rigid assembly defines a maximum outer diameter of the apparatus. In a second condition after expansion of the swellable member, the swellable member defines a maximum outer diameter of the apparatus. In a preferred embodiment the rigid assembly is designed to flex or deform under an axial or radial load.

Protecting tubular connections with an expandable tubular connection for use in a wellbore includes a tubular pin member. The tubular connection also includes a tubular box member having an end portion, wherein the tubular pin member is matable with the tubular box member to form the tubular connection. Additionally, the tubular connection includes a sleeve member disposed on the tubular pin member, wherein the sleeve member is configured to substantially protect the end portion of the tubular box member as the tubular connection is lowered into the wellbore.

Protecting tubular connections with an expandable tubular connection for use in a wellbore includes a tubular pin member. The tubular connection also includes a tubular box member having an end portion, wherein the tubular pin member is matable with the tubular box member to form the tubular connection. Additionally, the tubular connection includes a sleeve member disposed on the tubular pin member, wherein the sleeve member is configured to substantially protect the end portion of the tubular box member as the tubular connection is lowered into the wellbore.

The present invention relates to a hole opening tool to be used in oil well drilling. This tool is typically mounted on the lower end of a drill string and is rotated by adding rotating power to the drill string from the top end or by actuation of a down hole motor. A rotating drill bit produces a borehole at a diameter equal to that of the drill bit as the drilling proceeds downward.

In many cases, the earth formation may be relatively soft or subject to geometrical change. This change may take place due to absorbing moisture from the drilling mud. In such cases earth formation swells and narrows, choking the drill string movement and producing unwanted and potentially damaging negative torque. The present invention provides a hole opening tool that has:

- A steel body (1) having through axial bore for passing drilling fluid through (2).

- A straight stabilizing and reaming part (3)

- One tapered part above (4) and one tapered part below (5) the stabilizing part (3), both hold a number of cutters (6) to cut hole back to nominal size while drilling (5) downward or while pulling the drill string out of the hole (4).

A drilling string stabiliser tool comprising a cylindrical stabiliser body and a plurality of stabiliser blade assemblies mounted on the outer surface of said cylindrical body, wherein said stabiliser assembly comprises a stabiliser blade having an upper surface and side walls, wherein the stabiliser blade has an elongated shape with a front half having a front end and a back half having a back end, and wherein the average width of the back half of the stabiliser blade is substantially smaller than the average width of the front half.

Multilateral wells and improved multilateral well structures are made by setting a diverter (332) at a prescribed position and a prescribed orientation in a main well flow conductor (120) located within a main wellbore (110), boring through a sidewall of the main well flow conductor (120) and into a material (112) surrounding the main well flow conductor (120), the boring creating a window (324) having a particular shape in the sidewall, the orientation of the diverter (332) determining a lateral position of the window in the main well flow conductor (120), a lateral wellbore (150) thereby being formed in the material and extending from the main wellbore (110), and lining the lateral wellbore (150) with a liner (340), the liner having an interface end (342), the interface end being adapted to contact a periphery of the window (342) in the sidewall, and cementing the liner (340) in place within the lateral wellbore (150). The step of cementing creates a pressure-bearing seal between the periphery of the window and the interface end (342) of the liner (340). The method allows multiple lateral wellbores to be joined to the main wellbore and provides for connectivity among main and lateral wellbores, pressure-bearing sealing of joints to allow selective isolation of one or more wellbores or portions thereof and subsequent wellbore access for rework or other purposes.

Multilateral wells and improved multilateral well structures are made by setting a diverter (332) at a prescribed position and a prescribed orientation in a main well flow conductor (120) located within a main wellbore (110), boring through a sidewall of the main well flow conductor (120) and into a material (112) surrounding the main well flow conductor (120), the boring creating a window (324) having a particular shape in the sidewall, the orientation of the diverter (332) determining a lateral position of the window in the main well flow conductor (120), a lateral wellbore (150) thereby being formed in the material and extending from the main wellbore (110), and lining the lateral wellbore (150) with a liner (340), the liner having an interface end (342), the interface end being adapted to contact a periphery of the window (342) in the sidewall, and cementing the liner (340) in place within the lateral wellbore (150). The step of cementing creates a pressure-bearing seal between the periphery of the window and the interface end (342) of the liner (340). The method allows multiple lateral wellbores to be joined to the main wellbore and provides for connectivity among main and lateral wellbores, pressure-bearing sealing of joints to allow selective isolation of one or more wellbores or portions thereof and subsequent wellbore access for rework or other purposes.