CLE.SUB.ABZ.12.03.V2 WORLD´S FIRST HYDRATE MILLING ON E LINE, RLWI

Hydrate milling on e-line, RLWI

Background

A water injection well offshore UK was undergoing a start-up procedure when a build-up in wellhead pressure was observed indicating a possible blockage by a hydrate plug. Attempts to inject methanol through the injection master valve cleared the hydrate present between the flow valve and the wing valve. However, the hydrate was still confirmed as being present below the subsea tree, but the length was unknown.

The primary solution for removing the remaining hydrate was pipe pulse pressure technology with Welltec’s e-line solution as a contingency that could be carried out through a RLWI vessel.

After much consideration, the Welltec® Reverse Circulating Bit (RCB) for milling solutions was selected over any induced heat solution as it was thought to be less likely to generate rapid gas release from the hydrate allowing for a more controlled environment.

operation

After three days of sending pulses to break down the hydrates with no visible results, Welltec’s solution was rigged up. The scope of work was to restore injectivity and access through the wellbore by removing the hydrate.

The first toolstring consisted of a Welltec Release Device® 218, Well Tractor® 318 and a RCB 312 fitted with a 3.8” milling bit. The hydrate was tagged at 1,815 ft (553m) where the RCB was activated and milled down to 1,844 ft (562m).

A decision was then taken to remove the 3.5” stand-offs and run with the larger 4.2” mill bit in order to reduce the risk of sticking by creating a slicker tool. This solution effectively milled down to 1,997 ft (608m) when the operation was suspended due to adverse weather conditions.

Achievements

This was the world’s first milling of hydrate on e-line, proving yet another application of Welltec’s unique milling and cleaning solutions.

This capability has widespread application for operators around the world as a remedial approach for this complex problem. In less than 20 hours of actual milling time 173 ft (52m) of hydrates were removed to a depth that allowed the client to re-establish functionality to the downhole safety valve.

In less than 20 hours of actual milling time 173 ft (52 m) of hydrates were removed to a depth that allowed the client to re-establish functionality to the downhole safety valve.

Tools Applied

  • Well Tractor®

    The Well Tractor was regarded as a revolution in the industry when it was introduced in the 1990’s. It enables operators to extend the reach of traditional e-line deployment into highly deviated and horizontal wells.

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  • Welltec Release Device®

    Welltec Release Device (WRD®) is a simple tool which adds versatility and risk reduction to the operation. It provides predetermined locations in the toolstring where it can be parted, should it become stuck.

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  • Well Miller® RCB (Reverse Circulating Bit)

    The Well Miller RCB (Reverse Circulating Bit) integrates a rotary bit with a suction system to provide the combined benefits of both in one tool. This design breaks through objects and recovers the cuttings into the integrated bailers.

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