Innovative Unmooring Operations for Decommissioning FPSOs: Using Cutting of the Top Chain in Diverless Operation

Abstract The unmooring of P-32 and P-33 platforms carried out highlighted technological innovations that improved safety and operational efficiency. Innovative techniques were used on P-32, such as cutting the bottom and top chains with ROVs-tools, eliminating the need for diving and reducing risks for workers. This approach resulted in a time of 22 days of operation, being more economical compared to the traditional operation (without cut off the chains and using the mooring winch), which take 24 days, especially due to the dependence on favorable weather conditions. On the other hand, for P-33 the operation took only 13 days. This difference in time and cost between unmooring of the two platforms was expected, since the P-33 was designed with a diverless concept. Means that it's unmooring was carried out in the traditional way, that does not depend on diving or alternative techniques regarding to diving. Both operations used innovations (adapted grapnel and chain cutter) that simplified the unmooring process, reducing exposure to human and environmental risks and improving the predictability of the operations.