Abstract: An offshore oil or gas well riser system which forms a connection between the well head and a surface vessel. The system has a first riser section which extends vertically and is essentially rigid and a second riser section which is made of a flexible material to accommodate movements of the surface vessel. The first riser section has buoyancy means attached to its upper end to support at least partly the weight of the first riser section, and the first and second riser sections have corresponding first and second bores which provide a continuous path between the surface vessel and the well head. The profile of the flexible second riser section is variable to provide a smooth continuous path through its corresponding second bore and such that the path does not extend below the upper end of the first riser section.

Abstract: A coil tube and conduit system for feeding into a well has the coiled tube form an annular space closed at its top and herein a relatively dense liquid while the conduit is provided with buoyancy means so that within that coiled tube the conduit can be buoyed up by the confining liquid and hence the weight of the conduit relieved.

Abstract: A method of providing a casing in well from a series of casing sections. The first section is provided from the top of the well and the subsequent sections are arranged progressively downwards therefrom. The subsequent section to be fitted is lowered into the well by a suitable lowering tool, such as a coiled tubing runner. The well fluids which are displaced by the lowering of the subsequent section and the lowering tool, passes from the lower portion of the well up through the internal bore of the section to be fitted. The displaced fluids pass out from the internal bore of the lowering tool into an outside annulus between the lowering tool and existing casing through radial closable openings or side valves.

Abstract: The invention relates to a well casing 11 including at least two casing lengths 12, 13, 14, 15, 16 with a first casing section 12 having and outside diameter OD12 and an inside diameter ID12 being fitted and cemented in position extending downwardly from the top of the well. The remaining sections are installed subsequently each subsequent casing section 13, 14, 15, 16 having an outside diameter OD13, OD14, OD15, OD16 and an inside diameter ID13, ID14, ID15, ID16 and the diametrical difference D1, D2, D3, D4, D5 between the outside diameter OD13, OD14, OD15, OD16 of the sections 13, 14, 15, 16 being less that the internal diameter ID12, ID13, ID14, ID15 of the corresponding fitted sections 12, 13, 14, 15 being an amount which is just sufficient for the subsequent sections 13, 14, 15, 16 to pass down through the internal bore of the corresponding fitted section 12, 13, 14, 15.

Abstract: The invention relates to a guide arrangement 1 for a riser assembly 10 including a length of a second riser tube 6 running from a well head 2 to a surface vessel 6. First buoys 8 are provided which permit the evacuation and refilling of water to adjust the buoyancy effect and comprise a system to admit a controlled amount air or water and which are connected to the lower end of the riser assembly 10 by a first line 14 via a pulley 16 such that as the first buoys are raised the riser assembly 10 is pulled downwards towards the well head. Second buoys are provided to form a rigid frame work for the guide arrangement 1 when air has replaced the water contained therein. Support buoys 22 are connected to the first and second riser tubes 4, 8 by air line tubes 13 which enable air to be removed from and added to the support buoys 22 to adjust the amount of buoyancy they provide.

Abstract: A system for accessing a subsea well in which a guide on a buoy system is tethered to the well head and the buoy is evacuated to render the guide arrangement rigid and a flexible coil tubing from a surface vessel above the well head is guided through this arrangement to the well head while adjustable buoyancy is provided along the flexible tubing between the vessel and the well head for controlling the profile of the tubing.

Abstract: The invention relates to an releasable grip arrangement providing an impermeable barrier in an annular space between an inside tube and an outside tube of an oil well and is made of a material which may be dissolved by a suitable solvent and includes a seal member and a locking member 3, a sleeve which comprises holes which can be blocked during normal use but can be opened to permit the entrance of a solvent.

Abstract: A device is provided for controlling fluid flow in oil well casings or drill pipes. The device defines a flowpath for fluid through a casing section or drill pipe with the flowpath including a throttling valve which restricts or prevents the flow of fluid therethrough. This can be used to prevent U-tubing in casings or can be used to locate leaks in drill pipes or can be used to monitor the position of successive fluids of differing viscosities in a casing string.

Abstract: A tube assembly for servicing a well head injects an inner continuous coil tubing into an outer continuous coil tubing which can be connected at one end to a well head of an oil or gas reservoir. The inner coiled tubing can be connected to a tool string for servicing the well.

Abstract: A device is provided for controlling fluid flow in oil well casings or drill pipes. The device defines a flowpath for fluid through a casing section or drill pipe with the flowpath including a throttling valve which restricts or prevents the flow of fluid therethrough. This can be used to prevent U-tubing in casings or can be used to locate leaks in drill pipes or can be used to monitor the position of successive fluids of differing viscosities in a casing string.