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 was removed and the remains of the chamber were 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 immersed in seawater for so long; there was limited design 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, InterAct said, "We were faced with an uncommon well, constructed in an unusual fashion and about which there were a number of uncertainties. As part of formulating the abandonment programme, 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, "Good planning and technical analysis provided us with diving and abandonment programmes that were sufficiently detailed to include anticipated problems and appropriate mitigation measures, which minimised any ‘management of change' requirements." Sitek added, "The safety culture on the jackup, the diving support vessel and onshore was very healthy. This played a significant part in managing the technical challenges presented by this well and ensuring the operation was 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. The company also supervised the offshore work in conjunction with Centrica's offshore 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 were removed with the help of a diving team working from a separate support vessel. The scrapped well equipment was returned to Aberdeen for disposal.
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