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.

A carbon steel main body defines a flow passage. The carbon steel main body includes an end. The carbon steel main body includes a beveled edge at the end. A corrosion resistant cladding is deposited along an inner surface of the carbon steel main body. The corrosion resistant cladding extends from the end to a distance into the carbon steel main body.

A sealing system connecting first and second tubular members includes a first curvilinear sealing surface on the first tubular member and a second curvilinear sealing surface on the second tubular member. Both the first and second curvilinear sealing surfaces are disposed between two sets of threading on the respective first and second tubular members. When the first and second tubular members are in a connected configuration, the first and second curvilinear sealing surfaces contact and interfere to form an annular curvilinear center seal. A relief pocket may be disposed adjacent to the first and/or second curvilinear sealing surfaces to contain excess lubricant between the first and second tubular members.

A sealing system connecting first and second tubular members includes a first curvilinear sealing surface on the first tubular member and a second curvilinear sealing surface on the second tubular member. Both the first and second curvilinear sealing surfaces are disposed between two sets of threading on the respective first and second tubular members. When the first and second tubular members are in a connected configuration, the first and second curvilinear sealing surfaces contact and interfere to form an annular curvilinear center seal. A relief pocket may be disposed adjacent to the first and/or second curvilinear sealing surfaces to contain excess lubricant between the first and second tubular members.

A casing string includes an uphole section, a downhole section, and a sealed chamber that is fluidically isolated from the uphole and downhole sections. The sealed chamber extends between the uphole and downhole sections. The casing string further includes a tube that is disposed within the sealed chamber and that fluidically connects the uphole and downhole sections to provide a fluid flow path that extends past the sealed chamber and through the casing string.

A casing string includes an uphole section, a downhole section, and a sealed chamber that is fluidically isolated from the uphole and downhole sections. The sealed chamber extends between the uphole and downhole sections. The casing string further includes a tube that is disposed within the sealed chamber and that fluidically connects the uphole and downhole sections to provide a fluid flow path that extends past the sealed chamber and through the casing string.

An auxiliary line system for a drilling riser includes a first auxiliary line portion configured to couple to a first section of the drilling riser, a second auxiliary line portion configured to couple to a second section of the drilling riser, and a breech lock connection. The breech lock connection includes a first portion configured to couple to the first auxiliary line portion and comprising a first engagement feature and a second portion configured to couple to the second auxiliary line portion and comprising a second engagement feature. The breech lock connection is configured to adjust between a locked configuration and an unlocked configuration.

A sealing system connecting first and second tubular members includes a first curvilinear sealing surface on the first tubular member and a second curvilinear sealing surface on the second tubular member. Both the first and second curvilinear sealing surfaces are disposed between two sets of threading on the respective first and second tubular members. When the first and second tubular members are in a connected configuration, the first and second curvilinear sealing surfaces contact and interfere to form an annular curvilinear center seal. A relief pocket may be disposed adjacent to the first and/or second curvilinear sealing surfaces to contain excess lubricant between the first and second tubular members.

A sealing system connecting first and second tubular members includes a first curvilinear sealing surface on the first tubular member and a second curvilinear sealing surface on the second tubular member. Both the first and second curvilinear sealing surfaces are disposed between two sets of threading on the respective first and second tubular members. When the first and second tubular members are in a connected configuration, the first and second curvilinear sealing surfaces contact and interfere to form an annular curvilinear center seal. A relief pocket may be disposed adjacent to the first and/or second curvilinear sealing surfaces to contain excess lubricant between the first and second tubular members.

A control system for controlling disconnection of riser system that extends between a vessel and a subsea location that comprises a wellbore, the riser system configured to receive a string in use, the control system being configured to disconnect the riser system according to a sequence of operations, the sequence of operations comprising disconnecting the riser system prior to or simultaneous with cutting the string and sealing the well bore.