Environmental Impacts Assessment Associated with the Decommissioning of Fixed Offshore Platforms Using Life Cycle Analysis

Many oil and gas fields are now entering (or already have) into the twilight of their productive lives. Malaysia in particular has about 300 offshore installations in four regions; Peninsular Malaysia, Sarawak, Sabah, and the Malaysia-Thailand Joint Authority (MTJA), whereby 48% out of the total installations have exceeded their 25 years of service design life. However, there is insufficient information regarding the decommissioning of offshore facilities in Malaysia. Life-cycle assessment (LCA) is preferable to be used as it provides quantitative and structure 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 Malaysia using LCA tools; process LCA and Economic Input Output (EIO-LCA). Two offshore decommissioning options are studied; complete removal and also the re-use platform as an artificial reef. Both methods are studied and compared for their strength and limitations to obtain more reliable, representative and accurate results. The environmental impacts of an offshore decommissioning concerned in this study are the total energy consumption and also gaseous emissions (CO2, SO2 and NOx). Using EIO method, the results of LCA shows that the conversion to an artificial reef is the better decommissioning option in terms of energy consumption and gaseous emissions, whereas the process based LCA shows the opposite results. The decommissioning activity which mostly contributes to energy consumption and gaseous emissions were identified, which is the marine vessel utilization. The findings from this research provide a relative comparison between complete and re-use of the platform as artificial reef 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. To protect it for the future generations, the harm of the environment has to be reduced. In this case the environmental impacts could be less if the suitable decommissioning option is found based on numerous results by using LCA tools.