Abstract: An end fitting for a subsea riser comprises an engagement head to be engaged with a subsea foundation in a vertically downward longitudinal direction. A structure of the end fitting surrounds a longitudinally extending flow axis and is arranged to bear a tensile load on a load path extending longitudinally from the engagement head parallel to the flow axis. The structure includes a pivot joint assembly having a first part attached to or integral with the engagement head and a second part pivotable relative to the first part about a centre of rotation substantially aligned with the flow axis. The structure can be fixed to the engagement head or removably attached to the engagement head. The engagement head supports an upwardly facing connector hub that is offset laterally from the flow axis. A connector pipe in fluid communication with the connector hub extends from the flow axis to the connector hub. A counterweight is opposed to the connector hub and the connector pipe about the flow axis.

Abstract: 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.

Abstract: A pliant link to mitigate fatigue-inducing motion of a subsea catenary riser has an articulated spine having a longitudinal series of interconnected rigid segments. The spine can be coupled to upper and lower sections of the riser to transmit loads along the riser through the link on a load path that extends through the segments. The link also has a pliant pipe terminating in end fittings that can be joined, respectively, to the upper and lower sections of the riser for fluid communication along the riser through the link.

Abstract: A top connection arrangement for a subsea riser comprises a pivot or joint combination disposed between, and fluidly connecting, upper and lower sections of rigid pipe. The pivot combination composes an upper ball joint about which the upper pipe section is pivotable. A lower joint, being a flexible joint or a tapered stress joint to which the lower pipe section is attached, is fixed to the ball joint in series. A sleeve is fixed to the ball joint and surrounds the upper pipe section to permit limited pivotal movement of that pipe section about the ball joint. The sleeve may seat into the bellmouth of an I- or J-tube of a surface facility or may be omitted if the lower joint is seated in a hang-off formation. A locking mechanism is capable of locking the ball joint and hence preventing pivotal movement of the upper pipe section.

Abstract: An end fitting for a subsea riser comprises an engagement head to be engaged with a subsea foundation in a vertically downward longitudinal direction. A structure of the end fitting surrounds a longitudinally extending flow axis and is arranged to bear a tensile load on a load path extending longitudinally from the engagement head parallel to the flow axis. The structure includes a pivot joint assembly having a first part attached to or integral with the engagement head and a second part pivotable relative to the first part about a centre of rotation substantially aligned with the flow axis. The structure can be fixed to the engagement head or removably attached to the engagement head. The engagement head supports an upwardly facing connector hub that is offset laterally from the flow axis. A connector pipe in fluid communication with the connector hub extends from the flow axis to the connector hub. A counterweight is opposed to the connector hub and the connector pipe about the flow axis.

Abstract: A top connection arrangement for a subsea riser comprises a pivot or joint combination disposed between, and fluidly connecting, upper and lower sections of rigid pipe. The pivot combination comprises an upper ball joint about which the upper pipe section is pivotable. A lower joint, being a flexible joint or a tapered stress joint to which the lower pipe section is attached, is fixed to the ball joint in series. A sleeve is fixed to the ball joint and surrounds the upper pipe section to permit limited pivotal movement of that pipe section about the ball joint. The sleeve may seat into the bellmouth of an I- or J-tube of a surface facility or may be omitted if the lower joint is seated in a hang-off formation. A locking mechanism is capable of locking the ball joint and hence preventing pivotal movement of the upper pipe section.

Abstract: A top connection arrangement for a subsea riser comprises a pivot or joint combination disposed between, and fluidly connecting, upper and lower sections of rigid pipe. The pivot combination comprises an upper ball joint about which the upper pipe section is pivotable. A lower joint, being a flexible joint or a tapered stress joint to which the lower pipe section is attached, is fixed to the ball joint in series. A sleeve is fixed to the ball joint and surrounds the upper pipe section to permit limited pivotal movement of that pipe section about the ball joint. The sleeve may seat into the bellmouth of an I- or J-tube of a surface facility or may be omitted if the lower joint is seated in a hang-off formation. A locking mechanism is capable of locking the ball joint and hence preventing pivotal movement of the upper pipe section.

Abstract: A top connection arrangement for a subsea riser comprises a pivot or joint combination disposed between, and fluidly connecting, upper and lower sections of rigid pipe. The pivot combination comprises an upper ball joint about which the upper pipe section is pivotable. A lower joint, being a flexible joint or a tapered stress joint to which the lower pipe section is attached, is fixed to the ball joint in series. A sleeve is fixed to the ball joint and surrounds the upper pipe section to permit limited pivotal movement of that pipe section about the ball joint. The sleeve may seat into the bellmouth of an I- or J-tube of a surface facility or may be omitted if the lower joint is seated in a hang-off formation. A locking mechanism is capable of locking the ball joint and hence preventing pivotal movement of the upper pipe section.

Abstract: A pliant link to mitigate fatigue-inducing motion of a subsea catenary riser has an articulated spine having a longitudinal series of interconnected rigid segments. The spine can be coupled to upper and lower sections of the riser to transmit loads along the riser through the link on a load path that extends through the segments. The link also has a pliant pipe terminating in end fittings that can be joined, respectively, to the upper and lower sections of the riser for fluid communication along the riser through the link.