InterAct completes challenging subsea well abandonment in UK waters

InterAct, an Acteon company, has successfully completed the abandonment of an unusual well for Centrica Hydrocarbon Resources Limited in the East Irish Sea. Observation well 110/2-7 was drilled in 1983 and used to monitor temperatures and pressures in the South Morecambe gas field. The well was enclosed within a bathymetric chamber to enable divers to gain occasional access to the various gauges attached to the well. After a period of use, the well was suspended and, in 1999, part of the chamber removed and chamber left flooded.

Full abandonment after ten years posed a series of challenges. The well had been fitted with a surface tree and there were concerns over its condition after having been left in seawater; there was limited data on the chamber; the condition of the tubing in the well was suspect; and there were three mandrel control lines that extended down into the completion string, potentially affecting the ability to seal the well properly. Stuart Wordsworth, General Manager at InterAct, said, "We were faced with an uncommon well, constructed in a slightly unusual fashion and about which there were a number of uncertainties. As part of formulating the abandonment program, we carried out a scenario analysis to come up with contingency measures to deal with a series of problems that we thought might arise offshore."
 
Roman Sitek, Well Engineer, Centrica Energy Upstream, referred positively to this element of the project when he said, "Through a process of detailed planning and technical analysis, the diving and abandonment programs were sufficiently detailed to anticipate perceived difficulties and make appropriate mitigations with minimal Management of Change requirements."   Roman went on to add, "The safety culture on the jackup, the diving support vessel and onshore was very healthy and played a significant part in managing the technical challenges presented by this well, without accident or incident. The total engagement and professionalism of the offshore and onshore teams were critical to the successful execution of the work."
 
As well as designing the abandonment program, InterAct assembled many of the services necessary to execute the work and provided offshore supervision working in conjunction with the offshore Centrica Drilling representative. Several Acteon companies were sub-contracted through InterAct, and made essential inputs to the project: Claxton provided tooling for the work; OIS helped devise and manage the marine procedures; and 2H contributed riser analysis skills.
 
The project was completed between December of last year and January of this year. The well was killed and plugged from the Ensco 92 jackup drilling rig, and the 65 tonne bathymetric chamber and wellhead all removed with the help of a diving team working from a separate support vessel. This scrapped well equipment was returned to Aberdeen for disposal.

Centrica Commendation:

"We have now completed the successful abandonment of Well 110/2-7 Observation Well which in terms of difficulty was one of the most technically and operationally challenging wells on a global level having complexities both in the Diving and Well Abandonment processes. Through a process of detailed planning and technical analysis the diving and abandonment programmes were sufficiently detailed to anticipate perceived difficulties and make appropriate mitigations with minimal Management of Change requirements. The safety culture on the Jack-up, DSV and Onshore Support was very healthy and played a significant part in managing through the technical challenges presented by this well. This along with the total engagement and professionalism of Offshore and Onshore teams was a critical success factor in the execution management of the work. 
 
Job well done. Many thanks to all..." 
 
R.Sitek, WE, Centrica HRL

 

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