Abstract: Expandable and contractible buoyancy modules are assembled to the risers of a deepwater exploration spar or other offshore structure to provide an upwardly directed buoyancy force to offset at least a portion of the weight of the riser. The buoyancy modules have a fabricated pressure tight expandable and contractible envelope composed of rubber or rubber-like material which is mounted onto a tubular member having a central passage for receiving the riser to be supported. The tubular member projects beyond the respective upper and lower ends of the envelope and defines upper and lower riser joint connectors and buoyancy module travel stops which secure the buoyancy module to the riser and provide for force transmission from the buoyancy module to selected locations along the length of the riser or to the upper end of the riser.

Abstract: A wellhead system for petroleum producing wells comprises a “stack-down” casing hanger configuration. In this stack-down system, the hanger for each successively smaller diameter casing string is landed or “nested” within the hanger for the next larger casing string. This approach allows the pack-off for each casing hanger to be retrieved independently, thus allowing fluid communication to be established with any of the casing annuli after all of the casing strings and hangers have been installed. Thus the pressure in each annulus may be monitored while the well is in production mode.

Abstract: Expandable and contractible buoyancy modules are assembled to the risers of a deepwater exploration spar or other offshore structure to provide an upwardly directed buoyancy force to offset at least a portion of the weight of the riser. The buoyancy modules have a fabricated pressure tight expandable and contractible envelope composed of rubber or rubber-like material which is mounted onto a tubular member having a central passage for receiving the riser to be supported. The tubular member projects beyond the respective upper and lower ends of the envelope and defines upper and lower riser joint connectors and buoyancy module travel stops which secure the buoyancy module to the riser and provide for force transmission from the buoyancy module to selected locations along the length of the riser or to the upper end of the riser.

Abstract: The concentric tubing completion system of the present invention comprises a surface Christmas tree which is located on a surface structure, a tieback connector which is secured to a mudline wellhead that is installed at the upper end of a subsea well bore, a mudline tubing hanger which is supported in the tieback connector, and a pair of concentric tubing strings which are suspended from corresponding tubing hangers in the surface Christmas tree and connected to the mudline tubing hanger. The annulus between the concentric tubing strings communicates with a number of passages in the mudline tubing hanger which are connected to the tubing annulus below the mudline tubing hanger. Thus, lift gas or other fluids may be communicated between the surface christmas tree and the tubing annulus through this annulus between the concentric tubing strings.

Abstract: A wellhead system for petroleum producing wells comprises a “stack-down” casing hanger configuration. In this stack-down system, the hanger for each successively smaller diameter casing string is landed or “nested” within the hanger for the next larger casing string. This approach allows the pack-off for each casing hanger to be retrieved independently, thus allowing fluid communication to be established with any of the casing annuli after all of the casing strings and hangers have been installed. Thus the pressure in each annulus may be monitored while the well is in production mode.

Abstract: The concentric tubing completion system of the present invention comprises a surface Christmas tree which is located on a surface structure, a tieback connector which is secured to a mudline wellhead that is installed at the upper end of a subsea well bore, a mudline tubing hanger which is supported in the tieback connector, and a pair of concentric tubing strings which are suspended from corresponding tubing hangers in the surface Christmas tree and connected to the mudline tubing hanger. The annulus between the concentric tubing strings communicates with a number of passages in the mudline tubing hanger which are connected to the tubing annulus below the mudline tubing hanger. Thus, lift gas or other fluids may be communicated between the surface christmas tree and the tubing annulus through this annulus between the concentric tubing strings.

Abstract: A three-component adjustable mandrel well casing hanger that can be attached to the upper end of a tie-back sub or string to effect a tensioned connection between a subsea location and a surface wellhead of an offshore well.