A buoyancy compensating assembly and method of deploying a riser assembly are disclosed. The buoyancy compensating assembly for connection to a portion of flexible pipe, comprises at least one rigid buoyancy module for connection to a riser; and at least one regulating element configured to control the pressure within the at least one rigid buoyancy module in use.

An offshore well system for a subsea well includes an internal riser tension device configured to apply tension to an internal riser and an external riser tension device configured to apply tension to an external riser such that the external riser is supported at least partially independent of the internal riser tension device.

A flow modification device connectable to a generally cylindrical element adapted for immersion in a fluid medium, the device comprising an elongate body having a length and a generally circular cross-section; a plurality of raised body portions disposed about and extending along the length of the elongate body, the raised body portions being arranged generally parallel to a longitudinal axis of the body and having a height between 2% and 10% of a diameter of the body; and an aperture extending through the length of the elongate body, the aperture being adapted to receive the generally cylindrical element such that the flow modification device is arranged about the cylindrical element. The plurality of raised body portions are adapted to reduce vortex-induced vibration and/or drag on the cylindrical element when the device is connected to the cylindrical element and the connected device and cylindrical element are immersed in the fluid medium and there is relative movement between the connected device and cylindrical element and the fluid medium.

A wellbore self-retrievable tool for conveying and releasing a load in a well, the tool comprising: a floatation device; a load carrier; and a load release mechanism, the floatation device being configured to render the tool buoyant in a wellbore liquid.

A method of installing a wave-configuration subsea riser of unbonded flexible pipe comprises lowering the riser progressively into the sea from an installation vessel while suspending an elongate clump weight in a catenary shape that comprises first and 5 second limbs extending upwardly from a conjoining bottom portion. An upper end of the first limb, at a distal end of the clump weight, is attached to the riser and an upper end of the second limb, at a proximal end of the clump weight, is suspended from a winch or crane of the vessel. While lowering the riser from the vessel, the weight load applied to the riser by the clump weight is controlled by adjusting the relative lengths of the first 0 and second limbs of the clump weight.

Techniques and systems to reduce deflection of a riser suspended from offshore platform. A guidance thrust delivery system (GTDS) includes a plurality of thrusters configured to be coupled to a riser of an offshore vessel. Each thruster of the plurality of thrusters is configured to generate a force on the riser of the offshore vessel to control a position of the riser in a subsea environment while the riser is suspended from the offshore vessel and decoupled from a seafloor.

Techniques and systems to reduce deflection of a riser suspended from offshore platform. A guidance thrust delivery system (GTDS) includes a plurality of thrusters configured to be coupled to a riser of an offshore vessel. Each thruster of the plurality of thrusters is configured to generate a force on the riser of the offshore vessel to control a position of the riser in a subsea environment while the riser is suspended from the offshore vessel and decoupled from a seafloor.

Techniques and systems to reduce deflection of a riser extending from an offshore platform. A device may include a main tube disposed along a length of the device. The device may also include a support member that may be coupled to the main tube, wherein the support member may surround the main tube. The device may include a buoyancy assembly that may at least partially surround the main tube, wherein the buoyancy assembly may have an elongated non-circular and non-cylindrical shape. The buoyancy assembly may also include buoyancy foam.

A buoyant apparatus and method of use buoyancy to offset the weight of a load during immersion of the load in a fluid medium such as a payload manipulated by a cable and crane or by a remotely operated undersea vehicle. Buoyancy modules that can be of different size and shape have elongated supports that are attachable via complementary connection fixtures at the ends. The attached supports form a skeleton of the array. The connection fixtures are axially resiliently compressible and maintain the buoyancy modules in abutment notwithstanding shrinkage or expansion of the buoyant material due to hydrostatic pressure that increases with depth.