Unity, an oil and gas technology company, has announced a new method of pressure testing suspended mudline wells from a vessel, prior to well plugging and abandonment (P&A).

The company’s temporary abandonment cap test tool (TACTT) was deployed to support an end of life project located in the Southern North Sea. TACTT shows promise to deliver improved safety and cost savings.TACTT. Source: UnityTACTT. Source: Unity

According to Unity, it is the first technology that is able to seal on to any type and size of temporary abandonment (TA) 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 a 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 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-based, 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.

A recent report by the Oil and Gas Authority estimated that 45% of all decommissioning expenditure in the U.K. Continental Shelf is through P&A of wells and the industry is currently striving to reduce this spend by at least 35%. It is generally acknowledged that vessel-based intervention can save 30% to 50% in costs, compared to rig-based intervention.

Unity employs more than 130 skilled personnel across its bases in Aberdeen and Great Yarmouth, U.K., and Esbjerg, Denmark. It specializes in the provision of well integrity technology, services and engineering solutions for the global upstream oil and gas industry. Unity, is part of FrontRow Energy Technology Group.

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