A marine riser tensioner is a device used on an offshore
drilling vessel which provides a near constant upward force on the
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 (BOP) and generally us ...
independent of the movement of the floating drill vessel.
The
marine riser
Marine is an adjective meaning of or pertaining to the sea or ocean.
Marine or marines may refer to:
Ocean
* Maritime (disambiguation)
* Marine art
* Marine biology
* Marine current power
* Marine debris
* Marine energy
* Marine habitats
* Mari ...
is connected to the
wellhead
A wellhead is 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.
The primary purpose of a wellhead is to provide the suspension point and ...
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 cylinder
A hydraulic cylinder (also called a linear hydraulic motor) is a mechanical actuator that is used to give a unidirectional force through a unidirectional stroke. It has many applications, notably in construction equipment ( engineering vehicles ...
with
sheave
Sheave without a rope
A pulley is a wheel on an axle or shaft enabling a taut cable or belt passing over the wheel to move and change direction, or transfer power between itself and a shaft.
A pulley may have a groove or grooves between flan ...
s at both sides. The cylinder is connected to a number of high-pressure gas bottles via a medium separator. A
wire rope
Steel wire rope (right hand lang lay)
Wire rope is composed of as few as two solid, metal wires twisted into a helix that forms a composite ''rope'', in a pattern known as ''laid rope''. Larger diameter wire rope consists of multiple strands of ...
is rigged in the cylinder; one end is connected to the fixed part of the tensioner, the other end is connected to the riser.
[Fundamentals of Marine Riser Mechanics: Basic Principles and Simplified Analysis, Charles P. Sparks, ]
On board a drill rig tensioners are usually required for
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 ...
, riser tensioner, and
guideline tensioner.
See also
*
Hydraulic jigger
A hydraulic jigger is a hydraulically-powered mechanical winch.
From the mid-19th century, hydraulic power became available throughout the increasingly modern dockyards and warehouses. This was generated centrally and distributed by pipework, ei ...
References
{{DEFAULTSORT:Marine Riser Tensioner
Petroleum production
Drilling technology