Decommissioning Insight 2017

5.7 Well Plugging and Abandonment Costs The cost of well P&A depends on water depth, weather, reservoir type, age, condition and, in some cases, measures to prevent well collapse caused by depressurisation. The costs included in this report vary significantly in their degree of maturity. While some are informed by previous experience and data, other estimates are at an earlier stage of development and are inherently more uncertain. Oil & Gas UK has carried out analysis to look at the average and range in unit cost estimates for well P&A over the past five survey years. As shown in Figures 15 and 16 overleaf, the range is wide, particularly for subsea wells, although the average cost is relatively stable. Wells at the low-cost end are typically simple rig-less P&As, using wireline, pumping or crane jacks, where the reservoir may already have been isolated. Wells at the top end are more complex, rig-based P&As, with challenging access and cementing. They may require retrieval of tubing and casing, milling, and cement repairs. Since forecasts were made in 2016, the average unit cost for well P&A has fallen across all well types and regions of the UKCS. This reflects greater industry experience in this area as well as lower rig rates, which have fallen 30 per cent for jack-up rigs and 37 per cent for semi-submersible rigs over the past year. 5

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