DNV Software firmly believes it is on the right track when it comes to providing software tools and solutions to help designers and operators manage risks throughout an FPSO's life cycle, thereby ensuring continued fit-for-purpose asset condition.

Since the very first Floating Production Storage Offloading (FPSO), built from aconverted tanker in the mid-1970s and iinstalled offshore Spain, the oil industry has seen a steady rise in the number of FPSOs operating worldwide. While this growth has taken some time to get under way, the past decade or so has seen a period of rapid growth and a general acceptance of the FPSO technologies. The question is, will this growth continue?

The search for more oil is driving technology forwards, with much of the exploration and field development being undertaken in deep and ultra-deep waters. For this reason the future for FPSOs looks strong, as they currently present the only practical method of producing, storing and offloading oil at these greater ocean depths. It is not just deep waters that are driving the growth in the FPSO market. The ‘stability’ of high oil prices makes for ‘marginal’ oil fields becoming more financially attractive. A large number of these oil fields will utilise or have a demand for FPSOs. In recent times Brazil and West Africa have led the way, but now China, Australia, India, Indonesia, Malaysia, and even the Falkland Islands are expected to become sites for FPSOs.

As the Minerals Management Service (MMS) has approved the use of FPSOs in the Gulf of Mexico, we can expect FPSOs to provide a viable alternative to the TLPs and spars installed in the 1990s and early 2000s.

Motivation for a software and solution provider in the FPSO market
Where does DNV Software come into this picture? As a provider of tools for both CAE and operational asset integrity management, are we keeping pace with the ever-increasing demands placed on the use of such tools by the designers and operators of FPSOs today?

Since the late 1990s, DNV Software has adopted a strategy of offering the industry software tools and solutions, enabling both the designer and operator to implement, and re-use, best practice in their daily work. Such tools can also help in solving many of the challenges associated with selecting an FPSO for field development. DNV Software is further developing its FPSO Package for design and strength assessment of the hull, topsides, risers and moorings, and is at the same time developing its solutions for life-cycle structural integrity management of FPSOs.

Using conceptual technology and work process modelling
Key elements in enabling designers and operators to utilise experience feedback and implement best practice is through the use of conceptual modelling (of the FPSO and its subsea systems) together with life-cycle work process modelling. The concept model provides a means to store knowledge and information about a vessel, as it evolves from a drawing board design through to an on-site structure producing oil. It is used to derive the various analytical models needed to develop and verify the design, estimate steel and coating costs, and finally provide an information database for inspection, maintenance, and anomaly management throughout the vessel’s operational life.

Challenges for the FPSO designer
In recent years, with global yard capacity being under strain and many operators wanting to fast track field installation, the use of converted tankers as FPSOs has been one of the preferred solutions. Choosing a suitable tanker for conversion straight away poses challenges to the designer. He needs to know how much steel will have to be replaced; what the coating requirements are; what the remaining fatigue life is; will the hull safely resist the harsher environments it may have to operate in; does the hull have sufficient steel to meet the Ultimate Limit State (ULS) requirements of the Classification Rules for Offshore Ships?

To answer these and other questions, designers are turning to the FPSO Rule Check, Initial Design and Basic programs. Starting from a concept model of the vessel, these tools allow the user to quickly estimate how much steel needs to be replaced, what the costs will be for renewal of coatings, and check both the FLS and ULS to DNV Rules for Offshore Ships taking into account the environmental loading from the area of planned operation. As the design evolves and moves into detail design phase, the FPSO FEM and WAVE programs provide the tools needed to perform more complex analysis. Detail finite models may be spun off from the concept model to, for example, verify the mid-ship cargo hold area; check the topside to hull connection; and, for turret moored vessels, prove the turret design.

A proven solution for design of FPSOs
Many of the world’s leading designers have made DNV Software tools into a proven solution for design and analysis of FPSOs. Included among these are KBR, designer of the Terra Nova and Belanak vessels, and Sevan Marine, designer of the novel Sevan series of FPSOs

Challenges for the FPSO operator
Once on location, the operators of FPSOs face the challenges of ensuring fitness for purpose while complying with company operating policies and any regulatory requirements. Stable and safe operation is critical, with a minimum of shutdowns due to accidents or damages, periodic tank inspections, and planned maintenance. The integrity of the hull, topsides, and subsea systems needs to be maintained without the high expense incurred by docking as the risk of shutdowns, due to normal operations, increases with the age of the vessel. To reduce the risk of shutdowns, operators may use risk-based inspection to identify high-risk structural objects or components in the FPSO hull and topsides.

An asset integrity management system
DNV Software’s solution for asset integrity management has been developed to help the operator manage the risks during the life cycle of the vessel. Focusing on the inspection, repair, and maintenance processes, the system can be set up to cover the hull, topsides structures, process plant, and mooring and riser systems. Integrity information built up during the design, fabrication and installationcommissioning phases can be taken through to the operational phase by reuse of the concept or 3D model database. This database may be extended to include non-structural items, equipments, risers and moorings. This model is broken down into a hierarchical database of objects which, together with an associated graphical view model, allows easy navigation down to single items in the asset, such as for example ‘a section of a bulkhead in a water ballast tank’. The user can attach information associated with an object, such as past and future inspection plans, measured thicknesses, damage requiring attention, drawings and photographs, design data such as fatigue lives, and so on. The user can navigate this 3D model visually, quickly identifying areas requiring urgent attention through the use of colour coding of critical or high-risk objects. Such colour coding, often referred to as a ‘traffic light system’, can provide the operator and other stakeholders with an up-to-date status of the asset integrity, which can be viewed over an intranet or secure internet link.