A subsea catenary riser comprises a rigid riser pipe that is suspended from a floating support on the surface and extends through a sagbend to the seabed. A hang-off interface allows rotation or pivoting of the riser pipe relative to the support about mutually orthogonal horizontal axes. A subsea buoy is positioned on the riser pipe above the sagbend. The buoy applies buoyant upthrust force to the riser pipe via an attachment interface that allows rotation or pivoting of the riser pipe relative to the buoy about mutually orthogonal horizontal axes. In response to movement of the support, the riser pipe deflects with S-shaped curvature to vary the inclination, relative to the buoy, of the portion of the riser pipe to which the buoy is attached. The curvature comprises mutually opposed curves respectively above and below the buoy, joined by a region of inflection that coincides with the buoy.

Disclosed herein are novel buoyancy modules for attachment to a cable, pipe, or umbilical. The buoyancy modules include a pair of module bodies adapted to mate with each other. Each module body has a recess adapted to engage a single bolt tensioner and at least one of the module bodies includes a longitudinal channel running the length of the module body. Further, the module bodies include one or more pads positioned within a pad containment channel. A plurality of single bolt tensioners may be positioned within the recesses of the module bodies and tensioned to impart a compressive force such that the module bodies contact each other, generating a predetermined displacement of the pad and thereby imparting a known clamping force that results in a desired clamping pressure being applied by the pad to the cable pipe or umbilical.

A method of installing a subsea riser includes placing an elongate negatively-buoyant support on the seabed and, when laying the riser on the seabed, guiding a riser portion onto the support to extend along and be cradled by the support. A hogbend region of the riser is then formed by conferring positive buoyancy on the support to lift the support and the riser portion away from the seabed. An element of the support includes a riser support disposed in a longitudinally extending open-ended gap between buoyancy volumes disposed on opposite sides of the gap. Coupling formations such as hinge portions can couple the element to a like element. When so coupled, the gaps of those elements align to define an upwardly opening, longitudinally extending groove to receive the riser.

A buoyancy module (10, 12, 14) configured for mounting on an elongate underwater member (16) and provided with a sensor module dock (32) for receiving and releasably retaining a sensor module (30).

A spring (5;105;205;305;404;505) for a clamp suitable for attachment to a tubular member, the spring comprising a resilient body (6;106;206;306;406;506) having first and second ends (8;108;208;308;408;508) and an internal surface (7;107;207;307;407;507) adapted to seat within a clamp member and an external surface (9;109;209;309;409;509) adapted to contact the outer surface of a tubular member, the internal and external surfaces extending between the first and second ends and wherein the stiffness of the resilient body of the spring varies over the length of the body between the first and second ends.

A float apparatus includes a buoyant device that has an outer surface with a first end portion, a second end portion and an elongated portion. The elongated portion extends from the first end portion to the second end portion. The buoyant device is shaped and configured to attach to a conduit. The elongated portion of the outer surface has a concaved section that extends from the first end portion to the second end portion. The concaved section has a shape that complements an outer radius of the conduit with the buoyant device attached to the conduit.

A method of installing a steel catenary riser comprises progressively unspooling and launching the riser into water from a reel-lay vessel. The riser is plastically deformed in a straightening process aboard the vessel, downstream of unspooling and upstream of launching the riser. The straightening process is adjusted to form at least one residual curvature loop of locally increased curvature in a length of the riser that will be suspended in the water above a touch-down point in use. Ballast weights are then attached to the at least one loop. Buoyancy elements may be attached to the riser above the at least one loop.

Disclosed herein are novel buoyancy modules for attachment to a cable, pipe, or umbilical. The buoyancy modules include a pair of module bodies adapted to mate with each other. Each module body has a recess adapted to engage a single bolt tensioner and at least one of the module bodies includes a longitudinal channel running the length of the module body. Further, the module bodies include one or more pads positioned within a pad containment channel. A plurality of single bolt tensioners may be positioned within the recesses of the module bodies and tensioned to impart a compressive force such that the module bodies contact each other, generating a predetermined displacement of the pad and thereby imparting a known clamping force that results in a desired clamping pressure being applied by the pad to the cable pipe or umbilical.

Buoyancy module 102 may be positioned and adjusted on umbilical 402 without needing to recover umbilical 402 to topside for removing or setting the position of the buoyancy module. Buoyancy module positioner 100 is deployed and buoyancy module 102 positioned into a predetermined position within parking frame 108 by using buoyancy module holder 104 to selectively spool out umbilical 402 until buoyancy module 102 reaches a predetermined position along umbilical 402 relative to parking frame 108. Buoyancy module 102 can then be locked inside parking frame 108.