Floating production systems are on the hard edge of asset integrity management, says Jonathan Boutrot.
The business case for having an asset integrity management (AIM) system in place for offshore assets is getting more and more cogent every day.
CLOV Hull and Topsides integrated model in as-built state as a foundation for a structured AIM program. Images from Bureau Veritas.
There has always been a need to protect assets systematically and oil majors often have in-house asset integrity systems for their shore-based assets. But a conflux of pressures is making a formal, tailored and maritime-specific AIM system a must for both fixed and floating offshore assets.
The low and falling oil price is hitting capital expenditure, which means operators can build in less resilience to new projects and conversions. That means more care is needed during the life and operation of the asset. Regulatory pressure is increasing and public expectations are much higher, especially post-Deepwater Horizon. Operators of offshore assets need to be able to prove they have and are looking after assets safely.
And then there is life expectancy. This is where the big bulge in demand for AIM systems come. Many offshore assets, especially floating production, storage and offloading vessels (FPSOs), are reaching the end of their design lives. In the current market, there is little appetite to replace these with new units, but there is still oil and gas to recover. So the demand is there to squeeze a longer life out of ageing assets.
The design life of many FPSOs built since 1980 was 20 or 25 years. Feedback in service has shown that in some circumstances the design life was over-optimistic. As the industry moved quickly further and further offshore from the 1980s onwards, FPSO design did not always keep up. Some units have proven inefficient and difficult to maintain.
Today, as a bulge in the age profile of these offshore assets reaches and passes its design life, operators face a key question: is my asset suitable for life extension?
To make correct engineering and economic judgments on the life extension of FPSOs, operators need to know the full history of the unit. They need to have a clear picture of its current structure and condition and a prognosis of how that will develop in the future. Most importantly, they need in place a system that will monitor the asset during its life extension and ensure that the structure is behaving as expected.
The system required is a modern asset integrity maintenance system (AIMS), which encompasses a structural integrity maintenance system (SIMS). That means a planned and systematic way of building the data required to understand the condition of the structure and having in place an inspection and modeling system to keep that up to date.
It sounds simple, but in practice, because there are many contractual and other parties involved, a full AIMS and SIMS built up from the as-built condition is rare.
Total’s CLOV FPSO is the second project where Bureau Veritas has integrated certification of the topsides, risers and subsea installation with classification of the hull of the floater and one of the several floating assets where an AIM system was developed during the build phase.
For FPSOs being built today, operators can benefit from experience and begin to integrate a comprehensive AIMS process from the design phase, involving all parties. An example of that is Total’s CLOV, where Bureau Veritas integrated certification of the topsides, risers and subsea installation with classification of the hull of the floater and developed an AIM system during the build phase. When Total faces life extension issues in 25 years’ time, they will have the information they need to make sound decisions.
Tecnitas, BV’s advisory arm, was given responsibility for structural integrity management of the FPSO. This meant compiling a complete record of the construction detailing all non-conformities and preparing a full finite element model of the hull and topsides in as-is condition on delivery to Total. The model is the platform for of an ongoing risk-based inspection (RBI) program and an AIM scheme provide by Bureau Veritas. It will use VeriSTAR HLC software for tasks including inspection of relevant structural areas, assessing the corrosion condition of the FPSO against BV or user-defined criteria, and managing the data on the structure and topsides over the long term in an open format.
A big part of any modern AIM system is risk assessment. As we gain experience with offshore floaters in harsh deepwater environments we build better knowledge of offshore floating units and how they degrade over time. Feedback of their structural behavior over a long period of time allows us to improve the risk assessment. That makes for more cost-effective inspection and more targeted maintenance.
We are seeing an increasing demand for RBI plans as these improve because of the increase in built-in feedback. These are based on a semi-qualitative approach, with the analysis built on discussions with several experts (HAZID) who understand how the asset is operated, what the condition of the structure is, what the coating is like and what could be the consequences of a structural failure.
Classification society rules
VeriSTAR SIM (Structural Integrity Management)
AIM improvements built on RBI also have consequences for classification society rules. Class uses a prescriptive rule approach to define the tank inspection schedule, typically annual survey, intermediate survey every 2.5 years and class renewal survey every five years. This is being replaced by an RBI approach defining the inspection schedule. BV is now doing this for an oil major-operated FPSO off Angola.
RBI applicable parameters must include coating degradation, corrosion, fabrication quality control, fatigue and crack propagation, and well-thought through risk characterization, which measures each risk in terms of safety, the environment and the business impact.
BV is developing a qualitative RBI plan, including HAZID, to define a tank inspection schedule for one of the giant Nigerian FPSOs. In addition the oil major will use the VeriSTAR AIMS database including data management and inspection schedule and the VeriSTAR HLC (hull life-cycle) geometrical model for corrosion assessment and inspection management. RBI plans are also being developed for a complete field of fixed platforms in Asia.
AIMS and SIMS track ageing. Aging is not a matter of how old the equipment is, it is a function of what you know about its condition, and how that is changing over time. Indicators of ageing are many. There are frequent or recurring defects and failures, an increasing incidence of unplanned maintenance, repairs and breakdowns and signs of degradation. The plant may be down-rated or it may require increasing inspection and testing frequency to manage degradation.
The difficulty for operators, especially of older units, is that these indicators do not present themselves in a uniform or coherent manner, and the consequences of these indicators may fall into the different areas of responsibility of different areas of the company or project. The data about the indicators may be available, but it may not always be available to the people who can make sense of it or who need it to plan how to avoid an incident or downtime.
The tools and systems available to enable operators to know the condition of their asset structure and to monitor and predict how that condition is changing over time are what we call AIM and SIM systems.
VeriSTAR Hull Life Cycle screen shot showing 3D visualizer.
More than an engineering tool
The most important single thing about AIMS and SIMS is that they are not simply engineering tools for engineers. They are a cluster of software tools, inspection techniques, data management and data sharing platforms and good organizational practices. Each part alone provides only part of the solution, and to be effective all parts have to be embraced by the management of all the parties involved.
That is the difficult part of implementing an AIMS and SIMS process. There is a tendency to look for black box technical solutions. Good technical solutions such as 3D modeling and finite element modeling analysis are vital, but these tools only produce good answers if used by people willing to seek out and collate the right input information and the good answers only produce a better and longer-lived structure if they are understood and acted upon by the operators.
What new technology can do for AIMS is save time, improve traceability and reduce errors and omissions by reducing the human input. For example, the thickness measurements are today done manually by a surveyor who writes down values on a sheet of paper and then back in office populates the thickness values on a geometrical model or in an Excel table. Bureau Veritas is now testing new methods by using ROVs for the thickness measurements, linked with computers which automatically update a geometrical model.
The challenge for AIMs providers is to further develop the tools so they are coupled through each phase of the AIM system, open to connection at any stage with company and operator in-house systems and work in the same way for each area of the unit. That has to be done in the face of a cost squeeze and in a race against time as assets pass their design life.
Jonathan Boutrot is Offshore Development Manager at Bureau Veritas.