MONITORING LEAKAGES ON OIL PRODUCTION OFFLOADING AT OPEN SEAS USING STATISTICS ASSOCIATED WITH MASS BALANCE METHODS

摘要

With the increasing number of former VLCC (Very Large Crude Cargos) transformed into FPSOs worldwide, and its associated inherent oil production exportation characteristics to shuttle tankers, where very large flow rates are combined to the use of short and large diameters exporting lines, in many cases involving the use of hoses instead of flexible pipelines, and the obviously very sensitive environment, considering the execution of this transference in open seas, where losses for even a small period, regarded the involved exportation capacity means a huge spillage, with all its legal and image associated impacts, the challenge to identify and test technologies able to cany out the most effective leakage detection in this scenario was placed to PETROBRAS technical team, as consequence of rules demanding the installation of such systems stated by Brazilian Environmental Agencies. The proposal of this paper is to show the leakage detection solution based on a hybrid method combining mass balance along with statistical treatment adopted for monitoring the oil production offloading from the FPSO - MARLIM SUL, in the Campos Basin, Brazil, to a dynamically positioned shuttle vessel throughout a 150 meters, 20" diameter hose designed for a flow rate of 8.000 m3 per hour. A short description of this production system is provided, the operational principles of the adopted leakage system are depicted, its architecture is detailed, and the reasons that ended up leading PETROBRAS to adopt this technology amongst those others also considered are presented. Finally, comments about the installation, start-up and tuning, and considerations about the system observed behavior are made.