The present invention addresses to a system consisting of one or more pipes of low flexural rigidity (upper and intermediate extension pipes), connected to a thicker pipe section (lower extension pipe) by means of a varied cross-section pipe (conical profile) and further an adapter shaped like a helmet of a bend stiffener of a flexible riser, to enable, without operational losses, the use of rigid risers in Stationary Production Units (SPUs) initially designed to receive only flexible risers, therefore not having specific supports for rigid risers. The low flexural rigidity of the pipe is achieved through the correct selection of specific materials, preferably by using a titanium alloy that has a low modulus of elasticity and a high yield strength compared to steel.

A method approximates and connects an off shore riser duct to a floating unit, includes installing a tubular coupling recipient on the floating unit at a riser coupling level, the coupling recipient having an annular side wall extending around a longitudinal axis. A pulling device is on the floating unit at a pulling device level above the riser coupling level. The pulling device pulls a line extended through the coupling recipient and connected to a pulling head at a riser duct upper end. The riser duct upper end is pulled into the coupling recipient, providing a locking mechanism to lock a coupling adapter against downward withdrawal. Extending the line along a curved deviating surface deviates the pulling direction. The curved deviating surface is formed by a deviating member connected to the coupling recipient at a distance from the longitudinal axis smaller than an annular side wall to longitudinal axis distance.

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 cuter radius of the conduit with the buoyant device attached to the conduit.

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.

The invention relates to the fluid treatment, such as acid stimulation, of a subsea hydrocarbon well via a subsea wellhead/Christmas tree. Fluid is delivered directly to the subsea wellhead from a pumping vessel. Control of the delivery of fluid is from the pumping vessel via a fail-safe close valve in the delivery line. The Christmas tree subsea module is controlled directly from a host platform via a subsea cable, whilst a radio data link between the vessel and host platform provides communication of downhole data to the pumping vessel during the operation.

An apparatus (1) for restricting the bending of a tubular member underwater comprises a plurality of interlocking modules each formed from a first half shell component (2) circumferentially displaced from a second half-shell component (3), wherein the first half shell component comprises one or more projections (19) extending from a side edge (18) thereof and the second half shell component comprises one or more grooves (21) in a side edge (18) thereof, the projections and grooves being angled to the side edges of the first and second half shell components, the arrangement being such that when assembled together each of the one of more projections of the first half shell component are inter-engaged with a corresponding groove of the second half shell component to secure the two half shells together.

A method for controlling buckling in subsea pipelines involves identifying spaced-apart sections of a subsea pipeline suitable for controlled lateral buckling. Sets of buoyancy modules are installed at each spaced-apart section and are selected to support the spaced-apart sections of the subsea pipeline in a neutrally buoyant condition at the seafloor when the subsea pipeline is in service. Any buckling caused by thermal expansion of the subsea pipeline is distributed to two or more of the spaced-apart sections, causing the two or more spaced-apart sections to deflect laterally along the seafloor outwardly from an initial as-laid position.

The invention relates to the fluid treatment, such as acid stimulation, of a subsea hydrocarbon well via a subsea wellhead/Christmas tree. Fluid is delivered directly to the subsea wellhead from a pumping vessel. Control of the delivery of fluid is from the pumping vessel via a fail-safe close valve in the delivery line. The Christmas tree subsea module is controlled directly from a host platform via a subsea cable, whilst a radio data link between the vessel and host platform provides communication of downhole data to the pumping vessel during the operation.

This invention relates to oil and gas exploration and comprises a direct connection system referred to as a Lower Riser Termination Assembly (LRTA), between risers made of composite material and horizontal lines installed on the seabed (flowlines). The system is applicable to a hybrid riser and its construction method allows cost reduction and system assembly/installation time optimization. The LRTA connection system is applicable to both rigid and flexible flowlines without need for any intermediate connection section/equipment between these and the risers.

Another important feature of the presented system is the fact that its construction allows free vertical expansion of the risers along the entire structure.

In addition, while, in the state of the art, the conventional methods require a large assembly and construction area, in the construction method developed for this system, the required area is significantly reduced, approximately 10 times smaller than that required for known construction methods.

A downhole apparatus comprises a casing string with a removable plug therein to block flow therethrough. A flow barrier is positioned in the casing below the removable plug and the removable plug and the flow barrier defining a buoyancy chamber therebetween. A debris barrier positioned above the removable plug includes a frangible disk. A stretchable connecting ring is connected to the frangible disk and to the casing.