Bidvertiser

Loading...

FLOATING RIG SYSTEMS AND COMPONENTS

MOORING SYSTEMS
When a floating drilling rig is moved to a new location to drill a well, it must maintain that position as accurately as possible. Obviously, no floater could exactly maintain its station above
the chosen spot on the seabed under all enviromental conditions.
Mooring systems are therefore designed to keep the horizontal movement of the vessel within certain limits. The actual distance a vessel can move depends on the depth of the water.

TYPES OF MOORING SYSTEMS
  • Anchors and mooring lines
  • Dynamic positioning

Heave compensation unit is a device which is put into a hoisting system of a rig. It acts rather like a spring which extends as the vessel moves down. This movement is governed, to maintain a constant weight on the drill bit.
There are two basic types of heave compensators, the type that is mounted on the crown block.

HEAVE COMPENSATION SYSTEM
A compensator unit
A hydro/pneumatic operating system
An air supply system
A driller’s control console

COMPENSATOR UNIT
The compensator unit has upper yoke to which the travelling block is attached. Also connected to this assembly are one or two hydraulic cylinders.
From pistons acting in the cylinders, piston rods extend down to a lower yoke. The drilling hook is attached to the the lower yoke. The drilling hook is attached to the lower yoke. This locking mechanism is incorporated into the unit.  This is used to mechanically lock the unit in a closed position. It is used during round tripping etc when the heave compensator is not required.

HYDRO/PNEUMATIC OPERATING SYSTEM
The hydro/pneumatic operating system consists of an accumulator. An air bottle bank and a hydraulic fluid unit. The accumulator is a cylinder containing a free floating piston. From one side of the piston, hydraulic oil is fed to the compensator unit. To the other side of the piston, air presure is maintained from the air supply system.

WHEN VESSEL MOTION CAUSES THE COMPENSATOR UNIT
To stroke, fluid is forced in and out of the compensator cylinders and accumulator cylinder. This causes the floating piston to move back and forth. The air bottle bank provides a reservoir of high pressure air. The hydraulic fluid unit consists of a storage reservoir, pumps and top up system. The top up system maintains the fluid level in the accumulator at a safe level.

AIR SUPPLY SYSTEM
The air supply  system uses compressors and driers to supply high pressure air to the operating system. This air is also used in the tensioning equipment as you will see later.

GUIDE BASES
Most wells which are drilled from floating rigs require guidince systems. This allows drilling tools to be positioned at the right place on the seabed when drilling commences, and to enable re-entry when required. The most prevalent system uses two steel frames known as guide bases.

TEMPORARY GUIDE BASE
The first of these bases is called a temporary guide base (TGB). It is a steel construction having a large diameter pipe wielded through the center. The top of the pipe is shaped like a tunnel. Four steel cables called guide lines are connected to the the base at a radius of 6 feet. When the base is on the sea bed the guide lines terminate in some form of constant tensioning device on the drilling rig. Protruding from the bottom  of the base are short steel legs which dig into the seabed.

In order to start the well, the TGB is lowered to the seabed using a special tool called a running tool . Central pipe has four U shaped slots cut into it. The running tool is connected to the base using dogs which locate in the slots
The running tool itself is a circular which is screwed onto the drill pipe. It is attached to the base by inserting it into the central pipe so that the dogs engage the slots. The tool is then lowered and rotated
The movement is similar to the guide base for the whole assembly is lowered through the sea on the drill pie. The base is weighted with heavy materials so that it will not be affected by ocean current while it is being lowered.

Once the base has been landed  on the seabed, on the seabed, the running tool is released and recovered. The first action of the well can now be drilled.
ENGINEERING 5542498113667153461

Post a Comment

emo-but-icon

Home item

Bidvertiser

MOST RECENT POSTS