Riser tensioner
Encyclopedia
A marine riser tensioner is a device used on an offshore drilling vessel
which provides a near constant upward force on the drilling riser
independent of the movement of the floating drill vessel.
The marine riser is connected to the wellhead
on the sea bed and therefore the tensioner must manage the differential movements between the riser and the rig. If there were no tensioner and the rig moves downward, the riser would buckle; if the rig rises then high forces would be transmitted to the riser and it would stretch and be damaged.
Tensioners have historically been composed of hydraulic actuated cylinders with wire sheaves. More recently, active electrical motors have been used for compensation purposes.
with sheave
s at both sides. The cylinder is connected to a number of high-pressure gas bottles via a medium separator. A wire rope
is rigged in the cylinder; one end is connected to the fixed part of the tensioner, the other end is connected to the riser.
Onboard a drill rig tensioners are usually required for Drill string compensator
, Riser tensioner
, and Guideline tensioner
.
Drilling rig
A drilling rig is a machine which creates holes or shafts in the ground. Drilling rigs can be massive structures housing equipment used to drill water wells, oil wells, or natural gas extraction wells, or they can be small enough to be moved manually by one person...
which provides a near constant upward force on the drilling riser
Drilling riser
A drilling riser is a conduit that provides a temporary extension of a subsea oil well to a surface drilling facility. Drilling risers are categorised into two types: marine drilling risers used with subsea blowout preventer and generally used by floating drilling vessels; and tie-back drilling...
independent of the movement of the floating drill vessel.
Wellhead
A wellhead is a general term used to describe the component at the surface of an oil or gas well that provides the structural and pressure-containing interface for the drilling and production equipment....
on the sea bed and therefore the tensioner must manage the differential movements between the riser and the rig. If there were no tensioner and the rig moves downward, the riser would buckle; if the rig rises then high forces would be transmitted to the riser and it would stretch and be damaged.
Tensioners have historically been composed of hydraulic actuated cylinders with wire sheaves. More recently, active electrical motors have been used for compensation purposes.
Hydraulic Tensioner
A hydraulic riser tensioner consists of a hydraulic cylinderHydraulic cylinder
A Hydraulic cylinder is a mechanical actuator that is used to give a unidirectional force through a unidirectional stroke. It has many applications, notably in engineering vehicles.- Operation :...
with sheave
Sheave
A sheave is a wheel or roller with a groove along its edge for holding a belt, rope or cable. When hung between two supports and equipped with a belt, rope or cable, one or more sheaves make up a pulley. The words sheave and pulley are sometimes used interchangeably.A sheave can also refer to a...
s at both sides. The cylinder is connected to a number of high-pressure gas bottles via a medium separator. A wire rope
Wire rope
thumb|Steel wire rope Wire rope is a type of rope which consists of several strands of metal wire laid into a helix. Initially wrought iron wires were used, but today steel is the main material used for wire ropes....
is rigged in the cylinder; one end is connected to the fixed part of the tensioner, the other end is connected to the riser.
Onboard a drill rig tensioners are usually required for Drill string compensator
Drill string compensator
A drill string compensator decreases the influence of the heave of a drilling vessel on the drill bit. Drill string compensators are also known under the more general name: heave compensator. Drill string compensators are used onboard drill ships and semi-submersible drill rigs...
, Riser tensioner
Riser tensioner
A marine riser tensioner is a device used on an offshore drilling vessel which provides a near constant upward force on the drilling riser independent of the movement of the floating drill vessel....
, and Guideline tensioner
Guideline tensioner
A guideline tensioner is a hydropneumatic device used on an offshore drilling rig that keeps a positive pulling force on the guidelines from the platform to a template on the seabed....
.