New vessel-based pressure testing

Jon Lawson

A new method of pressure testing suspended mudline wells from a vessel, prior to P&A activity has been launched following a successful project for Spirit Energy.

Developed by Unity, the Temporary Abandonment Cap Test Tool (TACTT) was deployed to support an end-of-life project located in the Southern North Sea.

It is the first technology of its kind which is able to seal on to any type and size of temporary abandonment cap, pressure test the seal to ensure well containment, then test and vent pressure from below the TA cap and leave a reliable secondary seal in place. It can be cable deployed from a vessel through open water, rather than using a rig, providing significant cost savings.

During the project for Spirit Energy, the TACTT was deployed from a vessel, latched and sealed on to the TA cap and the seal was pressure tested. A second pressure test was then performed to provide verification of zero pressure under the TA cap’s back pressure valve. Once integrity was confirmed, this allowed the operator to safely continue with removal of the cap and complete its P&A operations.

The technology allows the operator to understand the amount of pressure accumulation below the TA cap and to accommodate this in their plans for decommissioning, either continuing with vessel-based intervention or leaving the TACTT safety valve in place and returning with a rig at a later date if necessary. Vessel- rather than rig-based P&A work is faster and more cost effective and Unity’s technology can help to enable this type of intervention by safely confirming no back pressure for well re-entry.

Gary Smart, Unity CEO said: “Decommissioning is the inevitable end-stage of any well, and although the industry is developing many solutions to extend producing life, we must also look to innovate further new technology to support operators’ P&A obligations. We developed the TACTT in response to operator demand, as there was no specific solution available on the market to pressure test suspended mudline wells behind their TA caps prior to removal.”


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