Cost and environmental impact estimation methodology and potential impact factors in offshore oil and gas platform decommissioning : a review

Platform decommissioning decision making is a major issue as many of the existing offshore oil and gas platforms (OOGPs) require to be decommissioned. The cost and environmental impact are two main criteria for OOGP decommissioning. This paper reviews OOGP decommissioning factors and the current estimation methodologies of decommissioning cost and environmental impact. Six factors are identified: (1) platform types and complexity, (2) decommissioning options, (3) technical approaches, (4) circumstances, (5) regulations, and (6) strategies, followed by a detailed review of the estimation methodologies of cost and environmental impact. Descriptive statistics are common cost estimation, together with standard-based and index-based cost estimations. For environmental impact estimation, qualitative methods like ranking decommissioning options based on expert option, and quantitative methods like emission calculation based on equipment utilization, duty cycles, and emission factors are commonly used. The findings of this paper indicate that current OOGP decommissioning databases are incomplete, leading to inaccurate and subjective decommissioning cost estimation, and incomplete environmental impact estimation. Recommendations include integrating 3D information modeling with cost indexing to estimate cost, and with life cycle assessment to estimate environmental impact. OOGP decommissioning regulations should include strategies and rules for estimation, and formulating a roadmap with a long-term perspective is necessary.