Subsea Pipeline Inspection, Repair and Maintenance

Introduction

Ever since the first subsea pipelines were installed engineers have been developing methods to inspect, repair and maintain them to ensure that they can safely transport the fluids required. Most of this development has focussed on the areas of saturation diving, remotely operated vehicles and pigging, with the technologies improving incrementally to meet the demands of deeper, hotter and higher pressure pipelines.

Current Market Situation

Until a few years ago the market for subsea pipeline IRM was serviced by a relatively few large contractors such as Technip and Subsea 7. These contractors were awarded long-term (usually 3+1+1) IRM contracts which enabled them to invest in new equipment, charter vessels and even purchase their own vessels in some cases.

The high oil prices between 2011 and 2014 caused spot rates to increase and this attracted new entrants into the market, keen for a slice of this lucrative business. This increase in competition inevitably caused a reduction in rates and this, coupled with the current oil price, is making life hard for many contractors.

We have also seen new operating companies in the North Sea buying assets, redeveloping them and also developing new fields. These operators are looking for more value from their IRM contractors and are pushing for more innovative inspection solutions.

On top of all of this there is increasing pressure on the whole industry to eliminate any health, safety or environmental incidents and minimise reputational damage.

Pipeline

The Adoption of Risk-Based Approaches

Historically, most subsea pipeline assets were inspected every year by divers or ROVs to maintain a record of their condition. Time-based inspections were also carried out on some pipelines using in-line inspection (ILI) tools. Over the last 10 years most operators have moved away from this prescriptive approach to a risk-based approach, this has been supported by the development of specific industry standards for subsea pipeline IRM such as DNV RP F116 (published in 2009) and BS PD 8010 part 4 (published in 2012).

The Challenges of Ageing Assets

As in all mature basins, the North Sea has many assets which are well beyond their original design life. These assets have been revalidated using a variety of inspection methods, many of which have been specifically developed to meet the challenges of such ageing infrastructure.

However, the challenge of ageing assets is not just in the engineering. Many ageing assets have changed ownership many times during their lifetime and IRM data has been lost or degraded, making it difficult to monitor trends. Many assets have also been fragmented with one operator owning the pipeline and another owning the riser and spool.

Alternatives to ILI and ROV Inspection

As margins get squeezed further, operators are seriously looking at more innovative inspection and monitoring solutions. A large number of such inspection and monitoring tools exist and recent development has brought some of them to the market. It was encouraging to see some of these tools being demonstrated at the Subsea Expo 2015. UK operators have usually adopted an “after you” approach to new technology due to the perceived risk, however some are now prepared to be first in order to reap the substantial cost savings.

One of the biggest paradigm shifts in subsea pipeline IRM would be the development of long life autonomous underwater vehicles (AUVs). AUVs have been used for pipeline inspection for over a decade, the most widely publicised being the Subsea 7/BP Autotracker™ system, their problem is that the battery life is still measured in hours. A lot of development work has been carried out by various oceanographic organisations to develop solar and wave powered AUVs but none of it has resulted in an AUV that can be launched from a slipway, travel along a pipeline and be recovered from the same slipway; eliminating the need for expensive support vessels.

The Future

In order to successfully maintain the integrity of the North Sea subsea pipeline network radical measures may need to be taken, here is one possible example.

In the UK the high pressure gas transmission pipeline network is owned and operated by National Grid plc (originally a nationalised company). This network runs at approximately 70 bar and transports dry gas from various locations around the coast (e.g. St Fergus, Easington, Milford Haven) to the local distribution zones around the country. Being owned and operated by a single company allows for efficient inspection, maintenance and operation of the network. Shippers (companies that supply gas) pay a transportation fee to National Grid based on the volume transported.

What if this model was applied to the UK offshore pipeline network? Ownership could be transferred to the OGA (or some not-for-profit organisation), they would then be able to manage the system in a holistic manner, achieving better economies of scale for inspection campaigns and applying a risk-based approach across the whole network. Operators would then pay a transportation fee (much in the same way that they do now to other operators to use their pipeline infrastructure) to get their product to the market (e.g. the onshore refinery or loading terminal). This approach would have many other benefits in improving the viability of new developments and reducing the cost of decommissioning. Of course there would be many legal and financial hurdles to be overcome to achieve this.

In the short term there are many other things that could be done to improve the management of subsea pipeline IRM. One “quick win” would be to improve the way that integrity data (e.g. corrosion rates) is shared between operators. Forums do exist for sharing best practice (e.g. the pipeline users group) but their effectiveness is often curtailed due to commercial or legal restrictions.

A more medium term objective is the development of intelligent pipelines. Such pipelines use embedded fibre optics and other sensors built into the pipeline structure and are able to provide real-time information on the pressure and temperature of the pipeline. Several organisations are currently working on this.

How Can Theon Help?

At Theon we provide a pragmatic approach to subsea pipeline IRM. We listen to our clients and determine the best approach rather than assuming that we know best. We then apply the solution in the most cost-effective manner. We quantify our findings in dollars and understand where the real benefits are so you get the most from your budget. We also understand the value of better data and know when to stop.

We think that experience counts so we have built a team of pipeline engineers with 20+ years’ experience in all aspects of pipeline and subsea engineering. We also have a wide range of experience in onshore pipeline engineering and work with the other Theon disciplines to provide an integrated approach.

About the Author

Jonathan Franklin graduated from Brunel University with a first class degree in Mechanical Engineering and is the Manager of the Subsea and Pipeline Studies team at Theon. He is a Fellow of the Institution of Mechanical Engineers and also a Chartered Manager. Jonathan has worked in the pipeline industry, both on and offshore for over 20 years. Having worked in engineering consultancies for most of his career Jonathan has led hundreds of studies in all aspects of pipeline engineering, providing insight into the whole life-cycle of pipelines. At present Jonathan is also working as a Technical Authority for a deepwater (1926m) pipeline project in Angola.

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