A Risk-Based Approach To Managing the Integrity of an Ageing FPSO Hull

Abstract The hull of any FPSO not only provides the platform for the production facilities and accommodation, but also incorporates the storage and offloading facilities for the field (and potentially other fields). As such the hull acts as a vital "hub", critical to both the operation and export chain. For FPSO's (like ships) there already exists an "experience based" prescriptive regime for integrity management of the hull structure (Class). This, however is based upon maintaining a minimum standard for a forecast window of only 2.5 to 5 years as per a trading oil tanker where opportunities to drydock the hull to carry out inspections and any required maintenance can easily be accommodated. Adopting this approach without due consideration of the constraints of FPSO operations imports a significant risk to the viability of an asset and does not guarantee the avoidance of having to go to dry-dock. Understanding the potential dangers of unquestioningly following Class rules and requirements, Hess have sought to adopt an alternative risk based approach to mitigate the risks to both integrity and operational functionality by proactively understanding the condition and limitations of the hull structure, putting in place an appropriate level of inspection, having robust assessment criteria and implementing increased inspection regimes or undertaking appropriate repairs to deficiencies identified in the hull structure. This paper presents the journey travelled by Hess from prescriptive Class rules to a risk based Class regime from the period 2006 to present. It will describe the asset; discuss Class rules and a risk based approach to integrity; and then describe how these are applied to the FPSO Sendje Ceiba. Hess Equatorial Guinea Overview Hess Equatorial Guinea operates the Ceiba and Okume Field developments. The Ceiba Field is comprised of subsea well clusters producing to FPSO Sendje Ceiba where the production is processed, stored and then offloaded through a CALM buoy. This field commenced production in 2000 and the license to operate expires in 2029. The Okume Field consists of 4 bottom founded platforms and 2 mini-TLP's. Okume production is fully processed prior to being exported via a 20 km pipeline to FPSO Sendje Ceiba for storage and offloading. This field commenced production in 2006 and the operating license will expire in 2032. Combined production from the two developments peaked at approximately 120,000 BPD and is currently in the range of 90,000 BPD. The FPSO serves as the storage and export terminal for both the Ceiba and Okume developments with an effective crude oil storage capacity of 1.78 million barrels. Liftings (sales) are made in 1 million barrel parcels. These developments are located offshore of the city of Bata which is located on the West African mainland just north of the equator as shown in Figure 1 below. The equatorial location of the developments results in a very benign operating environment devoid of named storms.