Application

This paper will discuss the successful use of a new "Rigless Intervention System "[RIS] as an alternative to the use of a Drilling Rig or Workover Rig for the Abandonment of Conductors, Pre Installation of Conductors, Sidetrack and Whipstock operations. The RIS system has also been used on a Tension Leg Platform for the pulling of Production Risers because deck load limitations ruled out the use of a workover rig.

With rigs becoming increasingly scarce, operators are being forced to delay abandonment and drilling plans for weeks, even months. For those operators with the foresight to anticipate this shortage, they have found an environmentally friendly hydraulic rigless intervention system as a means of extracting and pre-installing conductors without a rig.

The system has been performing for a number of operators in the Gulf of Mexico and internationally. The system reduces the amount of time and expense associated with installing conductors by pre-installing them prior to the arrival of the drilling rig, using the system to handle the joints and then for them to be driven with hydraulic hammers. On the conductor extraction side, the system speeds the process of abandoning multiple wells on fixed platforms.[See Fig. 1]

Modular mini-derrick.

The system operates like a modular mini-derrick. It can be broken down into sections that can then be transported by road and on average-size supply vessels. The sections are small enough so that a platform crane can easily lift them from a boat and assemble the system on the platform [See Fig. 2]. Once set up, the system performs tasks similar to that of a drilling rig, capable of lifting, pulling, driving and running pipe. It can even have a power swivel installed that extends the capabilities for well intervention purposes [See Fig. 3]. The greatest economic benefit of the system is that it can be rented for a fraction of the cost of an average rig. Another advantage is that it is much lighter than a conventional workover rig.

Industry situation.

In the Gulf of Mexico alone, there are approximately 4,000 platforms that must eventually be abandoned and removed in accordance with Minerals Management Service requirements. In view of this, the company recognized a gap in the market for a more efficient means of carrying out this necessary process. Traditionally, service companies have relied upon casing jacks to remove the conductors when abandoning a well. The RIS performs better than casing jacks when removing multiple conductors. Casing jacks can only pull ten-foot sections of conductors, and because they grip the outer wall of the conductor, sea growth must be stripped from the conductor to prevent slippage, making them more time-consuming to use.

Abandonment process.

The system includes a mast that measures 76 ft (23 meters) high and has a split block that is capable of lifting 250 tons. It can handle pipe measuring up to a 36-in. diameter, with all inner strings cemented inside the conductor. Also it can remove 50-foot (15 meter) conductor sections at a time, [See Fig. 4] which speeds the dismantling process. By pinning the conductor section and lifting it with bails and slings [See Figs. 5 & 6] less time is required to carry out the extraction process by enabling 50-foot sections to be cut and laid out. This also enhances the safety of the operations as the inner strings, which may not have been completely cemented, are pinned all the way through and therefore cannot drop suddenly in an uncontrolled manner.

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