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BEST ALTERNATIVE FOR RIGID OFFSHORE PIPELINES DECOMMISSIONING – A CASE STUDY

Abstract:

Once the end of the productive life of the offshore fields is reached, the evaluation of the best decommissioning alternative becomes a challenge due to the complexity and the diversity of the installations found in the Brazilian scenario. Decision-making problems like choice are difficult to solve, most of the time, there is not a single perfect solution capable of addressing all the criteria: technical, environmental, social, safety and economic. The main objective of this paper is to determine the best alternative for the decommissioning of a rigid submarine pipeline located in the Cação field (Espírito Santo basin, Brazil) with a multi criteria decision analysis (MCDA) called Preference Ranking Organization Method for Enrichment Evaluation (PROMETHEE). The following decommissioning alternatives are considered: leaving in situ with no further remediation, leaving in situ with rock dumping of pipeline ends, removing whole length by cut and lift, and finally, removing whole length by reverse S-lay. As a result, one hopes to get a ranking of options, from the best to the worst alternative.