Holy Grail of Offshore Decommissioning – Regulatory Approvals for Minimally Invasive, Cost Optimized Abandonment

Abstract Offshore decommissioning is a critical aspect of the energy industry, with significant financial implications. The forecast for offshore decommissioning expenditure from 2023 to 2032 is approximately $118 billion, with annual spending expected to exceed $14 billion by 2032. This represents about 3% of the total offshore exploration and production budget. This paper focuses on plugging and abandonment (P&A) of offshore wells, as well as the removal of platforms and subsea equipment. We explore the regulatory framework, items to be decommissioned, removal technologies, demand trends, and cost considerations. Regarding offshore wells, new decommissioning technologies offer significant cost-saving potential, particularly within the P&A of wells, which accounts for approximately 60% of total offshore decommissioning expenditure. Key technological advancements include rigless WL, CT and HWU well P&A, highly efficient casing milling or perf wash & cement casing penetration techniques for plug placement. As for platform and subsea equipment, technological advancements also aim to remove or repurpose infrastructure, where Innovations in cutting techniques and lifting technology further contribute to cost reductions. In terms of results and observations, delaying decommissioning spending is generally ill-advised, especially for the permanent P&A of wells. Costs can increase significantly if decommissioning is postponed by several years compared to P&A within three years after well production ends. Similarly, removal costs for platforms and subsea structures may escalate over time. Interestingly, even in regions with stringent regulations (e.g., the North Sea), obtaining approvals for technologically innovative solutions is feasible. Approaches like "rigs-to-reefs" and repurposing existing structures for renewables, CCS can lead to substantial cost reductions while ensuring environmentally sustainable outcomes.