A geotechnical approach to decommissioning the North Sea

Ikon Science white paper stresses importance of formation pressure analysis in well plug and abandon. An ‘overly strict’ following of the OGUK guidelines ‘can lead to poor technical choices’.

A recent report from Oil & Gas UK puts the annual expenditure on decommissioning in the UKCS at £1.5 billion. To date some 9% of UK platforms have been decommissioned, with an estimated £15.2 billion more to be spent over the next decade. The global market is put at around £67 billion.

Ikon Science, developer of RokDoc, has produced a timely white paper titled, ‘Meeting the Decommissioning Challenge, addressing the cost and safety issues of abandoning wells which investigates the geotechnical challenges of well abandonment in the context of safety and the regulatory environment.

Various ‘smart’ engineering approaches have led to substantial cost reductions in decommissioning large offshore structures, but these only represent a fraction of the overall decommissioning costs. The largest capital expenditure in decommissioning (50% of cost) is well plugging and abandonment. New, efficient P&A techniques are the easiest way reduce costs, as long as a ‘zero risk’ of integrity failures can be achieved. One concern is the long-term sealing requirements of an abandoned well, risks which can be assessed by in-depth analysis of log data, pressure data and other data such as drilling reports.

Formation pressure is key to evaluating these risks and here, Ikon’ database of well data and RokDoc analyses is claimed to offer tailored workflows adapted to regional and local data access protocols and formats. Initial focus is the UKCS where Ikon has analyzed some 6,000 wells.

The UK Petroleum Act of 1998 is the regulatory foundation for decommissioning. However, ‘an overly strict following of the guidelines can lead to poor technical choices depending on local pore pressure distribution’. Ikon provides ‘independent reviews and due diligence on proposed plans, evaluating plug placement suitability and optimizing P&A design’.

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