MULTI FUNCTION CIRCULATING TOOL
MULTI FUNCTION CIRCULATING TOOL
Multi Function Circulating Tool (MFCT), Clutch Type, has been developed for use in wells
where high circulation rates are required at various times to displace solids out of the hole. It allows
flow rates to be boosted at a liner top to increase the annular velocity of the wellbore fluid, thereby
increasing the cleaning action. It also allows the spotting of chemical pills and the change-out of
wellbore fluids to be carried out very efficiently. The tool is particularly suited to wells with small
liner diameters in which well clean-up operations are performed prior to running completions or test
strings. The tool can be run when drilling cement and milling/polishing liner top PBRs.
The Clutch Type MFCT gives the benefit of pipe rotation and circulation above a liner with the ports
open, whilst protecting the lower string from potentially damaging torque. When the tool is open,
only the drill string above the tool is rotated. When the tool is closed, the complete string can be
rotated with circulation directed through the bit or mill.
The tool does not require darts or balls to be pumped down the drill pipe and can be operated in the
hole as many times as required by simply slacking off or picking up the string.
The tool is also available with an integral Shut Off Plug as an option. When fitted with this plug, all
flow is directed through the ports when the tool is open and the flow path to the string below is
positively shut off.
Operation
The tool is operated in a similar fashion to a bumper sub used during drilling. It has a stroke length
of 15 inches. Running in the hole the tool is fully stroked out and any circulation goes through the
end of the drill string. Rotating torque is transmitted to the whole drill string (clutch engaged). The
tool has a shear ring installed (7,000 lbs (standard) 15,000 lbs, 20,000 lbs, 30,000 lbs or 40,000 lbs in the
3.1/2” IF tool and 20,000 lbs (standard), 7,000 lbs, 30,000 lbs, 40,000 lbs or 60,000 lbs in the 4.1/2” IF
tool) to prevent premature opening whilst running in hole or drilling.
The MFCT is run with a suitable ‘no-go’ device (liner top dressing mill, bearing sub or stabiliser)
below it so that the tool can be operated without putting the lower string in compression. When this
device lands on the liner top and the required weight is slacked off, the outer sleeve moves down
opening the fluid by-pass channel. The tool is now open and high circulating rates can be achieved
through the circulating ports. Rotating torque is not transmitted below the tool in this position
(clutch disengaged).
Circulation is restored through the end of the drill string by simply picking up weight and moving
the outer sleeve up. The open and shut cycle can be performed as many times as required without
the need for expensive trips out of the hole and the driller has immediate positive control of the
circulation route.
To avoid seal damage, the tool should not be opened or closed when there is flow through it. The
pumps should be switched off and the tool operated only after returns have stopped. In addition, to
avoid damaging the clutch mechanism, the drill string should also not be rotated, or have any
residual torque, when functioning the tool.