In the upcoming years, many offshore oil and gas installations around the world will be decommissioned as they approach the end of their economic production lives. Offshore installations decommissioning brings along environmental impacts. However, there is minimal published information on environmental impact assessment of offshore decommissioning. Life-cycle assessment (LCA) is preferable to be used as it provides quantitative and structured comparisons between decommissioning options, while addressing environmental impacts simultaneously. The main objective of this study is to determine and to quantify the environmental impacts associated with decommissioning of an offshore platform in North Sea using LCA tools, process LCA and Economic Input Output(EIO-LCA). Two offshore decommissioning options are studied; complete removal and partial removal. The environmental impacts of offshore decommissioning concerned in this study are total energy consumption and gaseous emissions (CO2, SO2 and NOx). For this research, data from an estimation of the energy consumption and gaseous emission for decommissioning of an offshore platform in North Sea is used as input data for LCA analysis. Cost data for decommissioning is obtained from a published report on decommissioning insights and EIO model is constructed using online model. Results from both process LCA and EIO-LCA prove that partial removal is a better decommissioning option over complete removal in terms of energy consumption and gaseous emissions. The findings from this research provide a relative comparison between complete and partial removal that shall help the owners of platform to decide suitable decommissioning option. For future LCA analysis, it is recommended to have a complete set of detailed and up-to-date data to produce a more comprehensive results.
Keywords: Offshore decommissioning; environmental impacts; life-cycle assessment; process LCA; EIO-LC
