As an offshore asset approaches its designed life, and hydrocarbon production tends to decrease to a non-economic level, the operators have two options: extend the field's life or decommissioning.

Decommissioning is the removal or abandonment of the field's assets. The process is complex and can be divided into five main pillars: wells’ plugging and abandonment, subsea structure decommissioning, umbilical/risers/flowlines decommissioning, topside removal, and jacket/hull decommissioning. The processes and alternatives depend on the field's characteristics, such as water depth, distance to coast, the weight of subsea equipment, wells’ history and condition, type of hull, as well as local legislation. All these nuances require comprehension regarding the decommissioning processes to target the most cost- effective alternative.

Decommissioning is a costly process. It is necessary to understand the whole development, calculate time for each step and map the daily rate of the infrastructures (boats and equipment) required to estimate the cost by its availability. Depending on the equipment's integrity assessment, the field's life extension can be feasible and should be considered a viable alternative. Based on that, the development of an integrated model based computational system can help abstract the enormous complexity faced in real life, allowing operators to choose the most economically attractive option for a brownfield.

This study aims to propose a methodology developed as a digital solution for analyzing alternatives of decommissioning based on user's input. The methodology consists of gathering the possibilities for decommissioning or life extension, applied to each of the main pillars. Based on the results, it is expected that the present work will deliver an important contribution to the industry regarding the adoption of integrated design practices for the technical and economic analysis of brownfields.

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