An expandable centralizer (8), comprising: a plurality of ribs, each having a first end (30A) and a second end (30B); a first expandable collar (10A) comprising a plurality of links (16) connected to the plurality of ribs at the first ends, at least some of the links of the first expandable collar being slidably coupled together; and a second expandable collar (10B) comprising a plurality of links (16) connected to the plurality of ribs at the second ends, at least some of the links of the second expandable collar being slidably coupled together, wherein at least the first expandable collar is configured to expand without substantial plastic deformation.

A downhole stabiliser (5), such as a drill motor stabiliser, comprises at least one reaming means and/or reinforcing means (10).

The present invention also relates to an assembly (30), such as a downhole drilling assembly (31), comprising at least one such stabiliser (5) and/or a drill bit (40,41) comprising a gauge bit (42) at or near a drilling end (45) thereof, and a connection means (46) for connecting the drill bit (40,41) to a drill motor assembly (60), wherein the drill bit gauge (42) comprises a substantially cylindrical portion having a length less than or equal to approximately 1.0 times the nominal bit diameter.

The present invention also relates to a novel locking mechanism (80), such as a lock and key mechanism, to allow locking of a shaft (70'), e.g. a motor drive shaft (71'), through or together with a stabiliser (5').

A downhole stabiliser (5), such as a drill motor stabiliser, comprises at least one reaming means and/or reinforcing means (10).

The present invention also relates to an assembly (30), such as a downhole drilling assembly (31), comprising at least one such stabiliser (5) and/or a drill bit (40,41) comprising a gauge bit (42) at or near a drilling end (45) thereof, and a connection means (46) for connecting the drill bit (40,41) to a drill motor assembly (60), wherein the drill bit gauge (42) comprises a substantially cylindrical portion having a length less than or equal to approximately 1.0 times the nominal bit diameter.

The present invention also relates to a novel locking mechanism (80), such as a lock and key mechanism, to allow locking of a shaft (70'), e.g. a motor drive shaft (71'), through or together with a stabiliser (5').

An expandable centralizer (8), comprising: a plurality of ribs, each having a first end (30A) and a second end (30B); a first expandable collar (10A) comprising a plurality of links (16) connected to the plurality of ribs at the first ends, at least some of the links of the first expandable collar being slidably coupled together; and a second expandable collar (10B) comprising a plurality of links (16) connected to the plurality of ribs at the second ends, at least some of the links of the second expandable collar being slidably coupled together, wherein at least the first expandable collar is configured to expand without substantial plastic deformation.

An expandable bow spring centralizer (8) having a first collar (10A) coupled to and spaced apart from a second collar (10B) through a plurality of bow springs (30) wherein a fin (32) is connected to each bow spring (30), and then connected to one or more adjacent fins (32) upon collapse of the bow springs (30) to form a restraining band (39) that may be ruptured, e.g., upon expansion of the expandable pipe string (80).

A kit of parts which is assembled to form downhole apparatus and a method of forming the same are described. The kit of parts comprises a swellable member, which expands upon contact with at least one predetermined fluid, and a connector. The swellable member has a first mating profile towards a first end and a second mating profile towards a second, opposing end. The connector has a mating profile configured to mate with each of the first and second mating profiles of the swellable member. The connector can therefore be connected to either the first and second ends of the swellable member. The connector may be an end connector, or may connect the swellable member to a second swellable member. In either case, the connector may define an arresting surface against which the swellable member abuts when expanding. The kit of parts can be adapted to and installed on any well tubular, and may form any of a variety of tools including a well packer, a centraliser or an anchor.

A downhole apparatus having a radially expanding portion and a support structure are described. The support structure comprises an attachment means for coupling to the apparatus and a support portion configured to be deployed from a first unexpanded condition to a second expanded condition by expansion of the apparatus. In one aspect of the invention, the downhole apparatus is expanded by exposing the swellable material to at least one predetermined fluid, and the support structure abuts the swellable material in its expanded form. A method of use and its application to a well packer, a hanging member, an anchor and a centralising apparatus are described.

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 turbine matrix sleeve (100) in accordance with the invention includes an inner cylindrical structure made up of a first material. The inner cylindrical structure may include multiple blades and multiple channels running between the blades along an outside diameter thereof. The inner cylindrical structure further includes threads, such as right-hand or left-hand threads, on an outer surface thereof. An outer layer, made up of a second material different from the first material, is integrally bonded to the threads. This outer layer may be optionally embedded with hardened inserts or buttons, such as PDC inserts, diamond inserts, TSP inserts, or the like. The threaded surface on the inner cylindrical structure significantly improves the bond between the outer layer and the inner cylindrical structure and creates a mechanical lock therebetween.

The sleeve extends the gauge portion of the drill bit (102) and is helpful to reduce lateral movement of the bit and prevent the hole from going undergauge.

The present invention provides a flow restrictor coupling 10 and a method of forming a flow restrictor coupling. The flow restrictor coupling 10 comprises a hollow tubular member 12 having at a first end thereof first means for engagement with an end of a first pipe and, at a second end thereof, second means for engagement with an end of a second pipe, wherein said hollow tubular member 12 is arranged to couple said first pipe to said second pipe and to provide for fluid communication therebetween, said flow restrictor coupling 10 further being arranged to present at least one aperture 26 in a wall of said hollow tubular member between said first and second ends, the aperture 26 having selectively variable dimensions for control of fluid flow therethrough.