Claxton and OIS Boost Decommissioning Capacity

Claxton has developed an extension module for its Suspended Well Abandonment Tool (SWAT), which should enable its sister company, Offshore Installation Services (OIS), to set deeper environmental and intermediate barriers.

Neil Watson, SWAT product leader, Claxton, said: “SWAT holds the Queen’s Award for Innovation in the UK, and the Petroleum Institute Platinum Award for Innovation. It is the first tool of its type, and is provided by Claxton in co-operation with OIS. In combining our proven SWAT tool with the new extension module, we have significantly increased the range of wells that can be abandoned using SWAT.”

The existing SWAT tool is deployed from a vessel of opportunity through the moonpool, eliminating the need for a drilling rig. It is positioned on the wellhead and then used to perform casing perforation, recovery of drilling mud and placement of the required cement barriers in the well.

SWAT utilises the extension module to enable cement to be positioned even deeper within the well. A wiper plug is positioned before and after the cement column, which ensures that the wellbore is cleaned ahead of the cement. The lower plug forms a base for the column and slurry is uncontaminated when it enters the annulus. The cement is then displaced to the required depth in the well. In OIS’ most recent well abandonment campaign, the depth was 2400 feet below mudline. This added depth capability enhances well decommissioning capacity; previously, the SWAT tool was limited to environmental barriers up to 600 feet below mudline, which limited the wells eligible for abandonment with SWAT.

OIS completed its 18th multi-operator plug and abandonment (P&A) campaign for Centrica Energy and Antrim Energy in the central North Sea, using Claxton’s new SWAT extension module. Ten subsea wells in categories 1, 2.1 and 2.2 were abandoned with the rigless method.

Valerio Percoco, vice-president business development, OIS, said: “This project is the largest well decommissioning campaign completed by OIS since Acteon sister company, Claxton, introduced SWAT in 1996. The successful completion of this project, with zero environmental or lost-time incidents, reinforces our position as a global leader in the vessel-based P&A market, having safely abandoned 128 wells over the past 19 years. Furthermore, this multi-operator approach enables operators to share project costs, which, when combined with the rigless approach, provides a cost-effective method for decommissioning non-revenue generating assets. Project costs are divided equally between operators on the basis of number of wells brought to the campaign, and lump sum costs such as mobilisation and demobilisation are shared.”

OIS conducted offshore operations from an anchor-handling tug supply vessel (AHTS) the Island Valiant. In phase one, Claxton’s SWAT system was deployed through the vessel’s moonpool to perforate, circulate and set cement barriers in the bore and across all the casing annuli.