The Below Rotary Table Snubbing Unit
A project presented by Jean-Luc Puyaubran, Benjamin Lai & Wouter Gerrits
Suspended to a jack-up rig, the new Below Rotary Table Snubbing unit makes snubbing operations safer and simpler. The system makes these operations twice as efficient, and they can be carried out more quickly at a lower cost.
An innovative solution to simplify difficult operations
The new Below Rotary Table snubbing solution is mounted directly under the rotary table of an jack-up rig.
A first in TotalEnergies, this trail-blazing duo was used in operations by TotalEnergies Exploration & Production Netherlands in 2018 and then again in 2019-2020, in several operations on wells in its brownfield gas fields in the North Sea. Snubbing - or pressurized well intervention - consists of introducing tubular elements into active wells whilst containing their pressure, in order to extend the production of mature fields. The latest campaign added gas reserves of 2.2 Mboe and extended the lifetime of the affiliate’s main assets by 10 years.
Until now, this difficult operation has been undertaken using a unit with concentric actuators installed above the well, supported by guy wires and equipped with a narrow nacelle exposed to the elements 25 meters above the production platform.
The Below Rotary Table snubbing unit is a game-changer
- Guy wires are no longer required to position the unit: it is installed from the rotary table of the jack-up rig, requiring no work above sea and almost no work at height.
- The unit is fully digital and can be controlled remotely from the a panel installed in the driller’s cabin and is equipped with a interlocking safety system, which prevents any incorrect manipulation of the tubings.
- Pipes are run from rig floor as any normal jack-up run in hole operation, no load hanging from / to the Gin pole as for conventional snubbing units, no pipe singles being transferred over working areas.
- The solution has the advantage of combining the drilling unit and snubbing mechanism s, so that it can be adjusted in accordance with the characteristics of the tubings to be introduced.
- A jack-up rig with a large well center and jacking cylinders are used to bring the unit back up and suspend it in a protected area.
- The unit can be moved easily transferred from one well to another by using the jack up skidding system, in less than 12 hours, as against sometimes seven days for a classic unit.
Safer and more efficient snubbing
- Snubbing in this way increases our operators’ safety. They work in a closed, safe area, protected from the elements by the wind walls of the drilling unit. The risk of objects falling is reduced, equipment handling is safer, and evacuation is easier in case of an emergency.
- The well can also be controlled more efficiently: the use of drilling equipment facilitates pumping, the venting of gas and the handling of fluids.
- The logistics support required offshore is lessened, which also helps to reduce the carbon footprint of our activities.
- The new system gives a 30-60% greater operating window. It is designed to work 24/7 and in the most difficult weather conditions - with a capacity to continue operating in winds of up to 50 knots as opposed to 25 knots previously.
- Its operating efficiency is doubled: the tubings can be inserted in the well 2.5 times faster, at up to 140 meters per hour, compared to a standard unit.
- This new system is more cost-effective than a classic unit - although its initial cost is the same, it has a significantly higher efficiency. The most recent campaign undertaken in the Netherlands was completed 35 days earlier than scheduled at a final cost of 25% below initial budget.
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