Design of an Integrated Sustainable Energy System

Abstract One of the greatest industrial challenges for the oil & gas sector to address is the decommissioning of offshore assets along mature basins. The O&G Decommissioning sector highlights a key focus on low-carbon opportunities to reduce decommissioning costs, achieve ambitious emission targets, and accelerate the energy transition. This paper seeks to exploit synergies between the oil & gas and renewable sectors to reduce costs associated with oil and gas decommissioning. Firstly, the study employs a geospatial-based multi criteria site selection to identify potential energy hub locations. Secondly, assessing the techno-economic feasibility to repurpose O&G facilities as an alternative to decommissioning. A multi-criteria decision approach is employed combining weighted linear evaluation and NPV analyses on the selected offshore Southern North Sea (SNS) asset. This provides a comparative assessment of decommissioning alternatives and potential cost benefits of repurposing for renewable energy production alternatives to the ‘Business-as-usual’ decommissioning case. Repurposing the offshore platform from wind and hydrogen production with onshore methanation was found to be the most viable alternative with an estimated potential Net revenue of £146,013,922 per annum to be received as profit over an expected 10-year production. Furthermore, performing a Benefit-To-Cost ratio evaluation combined the financial and non-financial considerations to compare the benefits derived from competing alternatives. Altogether, the BTC ratios are estimated for repurposing for wind and hydrogen production, complete removal, and partial removal to obtain the values 0.000001897, 0.000002457, and 0.000005053, respectively. The BTC ratio of repurposing for wind and hydrogen production with onshore methanation presents the highest value of 0.000001438 in comparison to the other decommissioning alternatives. This paper presents a novel viable alternative to decommissioning mature oil fields through repurposing assets to renewable energy production sites. The proposed model presents the opportunity to offset carbon emissions and reduce decommissioning costs. The methodology applied to the Southern UKCS North Sea is applicable to ageing platforms worldwide given the availability of renewable resources for integration.