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Case study

Rapid leak detection for subsea production and storage sites

Supermajor international energy company

January 25, 2023

The ocean is a critical habitat that needs protecting. With decades of experience in sonar detection systems, our technologies provide an essential early subsea leak detection and warning system, across your oil and gas assets, CO₂ storage and offshore hydrogen transport and storage sites.

The challenge

A supermajor international energy company, with production infrastructure in more than 2,000 m (6,500 ft) of water depth, wanted a single subsea leak detection system that could be permanently installed to detect and localise, within seconds, oil or gas leaks across a wide area of its subsea infrastructure.

Existing sonar-based solutions are mostly based on sensors attached to subsea assets to detect leaks at specific or very localised locations, i.e. within a few metres. Alternative, non-acoustic, systems rely on anomalies in production data rates, which can be challenging should the leak occur upstream of the monitoring device.

At worst, leak detection relies on viewing the leak at the sea surface in the form of an oil-based sheen – when it’s already too late. This option is also limited when it comes to detecting leaks at gas producing fields and offshore carbon capture and storage (CCS) sites.

With a globally significant installed and aging asset base, as well as new infrastructure in the form of offshore CO₂ and hydrogen transport and storage, there’s increasing interest in alternative leak detection technologies that can operate autonomously and sustainably over wide areas in all water depths.

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The solution

Developed by Wavefront Systems and manufactured and commercialised by Sonardyne, our Sentry Integrity Monitoring Sonar (IMS) is the only commercially available wide-area subsea leak detection system. A single Sentry head can provide 360-degree coverage of a 1,200 m diameter area, or more than one billion cubic feet of seawater, automatically alerting the operator as soon as an oil or gas leak is detected.

Detection rates are very impressive, with Sentry being able to detect monophase gas down to 0.1 litre per minute (equivalent to around 1 barrel of oil per day) or monophase oil to 1 litre per minute (equivalent to 9 barrels of oil per day). That means operators can react quickly to an infrastructure integrity breach before it becomes a bigger environmental and financial problem.

Sentry is an active acoustic-based solution that is based on a remotely operated vehicle (ROV) deployable low-power sonar proven for long-term monitoring. It’s available as a wired solution, that can be connected via existing subsea infrastructure directly into a surface asset. There, a Sentry workstation with graphical user interface (GUI) is able to provide users with clear real-time and automatic alerts of any oil or gas leaks.

It’s also available as a wireless, battery-powered solution for semi-permanent deployment, with data transmitted acoustically to a topside transceiver system. The transceiver can be deployed from a platform, buoy, vessel of opportunity or, now more commonly, via uncrewed surface vehicles (USVs).

The results

To make sure Sentry was fit for the oil major’s needs, the operator oversaw a trial deployment of a hardwired Sentry IMS. This included using a simulated monophase oil target, in this case nitrile-rubber strands, equivalent to a nominal oil leak rate of around 150 barrels per day.

The trials provided fast and accurate results. Detection and classification of the equivalent release of 100 barrels of oil per day out to 245 m (820 ft) was achieved, a distance constrained only by limitations of the trial set up. Leak detection was alerted within seconds of the simulated leak skid being deployed.

Sentry’s capability, however, covers 100 barrels per day mono-phase oil leaks at distances of up to 740 m (2,427 ft). It is even more sensitive to mono-phase gas leaks, with the system being capable of detecting down to the equivalent of just 1 barrel per day at 500 m (1,640 feet) or 100 barrels per day (as measured at depth) at 1,000 m (3,280 ft).

Following the extensive and successful trials, the operator purchased the Sentry IMS system for installation at its deep-water field development.

Supporting the energy transition

As we transition from fossil fuels to new energies, many are looking to offshore as potential sites for CCS, as well as for hydrogen production. Sentry helps to de-risk these projects. It ensures that, should carbon sequestration and offshore hydrogen transport and storage sites develop a leak, their operators will be alerted quickly, enabling a swift response, preventing larger environmental and financial problems.

Read about how we proved subsea leak detection capability for carbon capture and storage sites (CCS) through an Energy Technologies Institute research project, with partners Fugro, National Oceanography Centre, British Geological Survey and Plymouth Marine Laboratory here.


Key Stats

360-degree coverage

1,200 m diameter area

0.1 litre per minute gas detection

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