Platform Decommissioning: Case Studies in Pipeline Network Reconfiguration
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Inline isolation tools have been safely used over many years as an alternative to inert purging (depressurising and water filling) and intrusive isolation techniques. During pipeline and platform decommissioning, inline isolation avoids large pumping spreads, push-back management, inert gas or glycol filling with long pig trains, and the flaring of many cubic metres of gas or disposal of other product. In addition, it minimizes the personnel requirements compared to intrusive isolations. Inline isolations can also be used for line replacement, tie-ins, valve change-outs, pipeline reconnections and other operations where assets are connected and the pipelines must remain pressurized during intervention. By avoiding shutdown and allowing production to continue, inline isolation presents significant benefits in terms of schedule and cost compared to conventional methods. As assets age and decommissioning becomes more frequent, this type of intervention will play a key role. This paper presents the current requirements (governmental and regulatory) for decommissioning and how inline intervention can help minimise operational disruption for those assets that remain, minimising the potential environmental exposure and also human risk. To highlight the benefits, the paper presents three case studies where non-intrusive inline isolation tools facilitated offshore decommissioning activities. Two of the case studies concern asset decommissioning in the North Sea, where some of the oldest offshore infrastructure is located. The third case study is related to decommissioning a subsea pipeline in the Gulf of Mexico. The paper concludes with considerations that offshore operators need to focus on and how inline isolation technology can assist in platform decommissioning and pipeline network reconfiguration.
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