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The largest ever controlled release of carbon dioxide CO₂聽from an underwater pipeline is to be conducted at DNV GL鈥檚 full-scale Spadeadam Testing and Research Centre as part of an international joint industry project (JIP) called Sub-C-O2.

Scheduled to start in early 2016, the planned release will mark the second phase of experiments at the Spadeadam test site, which is situated in remote Ministry of Defence land in Cumbria, UK. The tests are designed to increase industry understanding about environmental and safety effects of underwater CO₂ releases from pipelines.

The eventual aim is to develop safety guidelines for offshore CO₂ pipelines, which are expected to proliferate as carbon capture, utilisation and storage (CCUS) technology is eventually installed to mitigate CO₂ emissions from power plants and large industrial sources. CO₂ transported in offshore pipelines is also being used for enhanced oil and gas recovery.

鈥淐ombining knowledge of the consequences of underwater release with the probabilities of these events occurring will enable developers to improve designs and reactive measures to manage such events,鈥� said Russell Cooper, Technical Services Manager at National Grid.

The British electricity and gas company is in the vanguard of researching and testing pipeline capabilities for CO₂ transportation, and has test drilled a subsea CO₂ storage site offshore UK. Its work has helped to demonstrate significant storage potential in the southern North Sea.

It is participating in Sub-C-O2 alongside Norway鈥檚 Gassnova, Brazil鈥檚 Petrobras, the UK government鈥檚 Department of Energy and Climate Change, and DNV GL. Italy鈥檚 Eni plans to join the DNV GL-led JIP in 2016.

First experiment

The first experiment at Spadeadam involves small-scale, controlled CO₂ releases from a 3 in. nominal bore pipeline in a 8.5 m dia., 3 m deep water tank. Launched in September 2015, this phase was scheduled to complete by December the same year.

鈥淯nderwater cameras and other measurement techniques show us the configuration and characteristics of the plume of released gas, whether it reaches the surface, and what happens there,鈥� said Dr Mohammad Ahmad from DNV GL鈥檚 office in Groningen, the Netherlands, who project manages the JIP.

鈥淲e also measure water temperature, pressure, water pH and dispersing CO₂ concentration. The experiments will provide valuable information on the effects of the plume below the surface, and on the level of any toxic gases in the air above.鈥�

In general, higher concentrations of dissolved CO₂ tend to make water more acidic, with potential implications for marine ecosystems.

Second experiment

The second experimental phase running for three months from early 2016 will involve releases in a 39 m dia., 12 m deep pond at Spadeadam to study the effects of depth on measured and observed parameters.

鈥淭his is a huge pond,鈥� Ahmad said. 鈥淚t is the largest experimental investigation to date of underwater CO₂ releases. It is designed around what is known about underwater natural gas [methane] leaks. We will be curious to see if and when we may get CO₂ hydrates collecting on pipework.鈥�

Spadeadam is one of a network of 18 laboratories and testing centres operated by DNV GL on three continents. The facility provides companies with the rare opportunity to demonstrate whether equipment and components are fit for purpose, to test new products, techniques or processes, or to provide data to validate computer models.

鈥淭he world class team and facilities at Spadeadam have made DNV GL our 鈥榞o to鈥� organisation throughout our extensive programme of experiments to understand the requirements of CO₂ transportation,鈥� Cooper said.

The JIP was conceived and initiated by DNV GL鈥檚 Groningen office, and designed in collaboration with Spadeadam. Other offices in Oslo, Norway, and London, UK, have conducted physical modelling for the project.

Experimental findings are shared periodically with JIP participants so that next steps can be refined. Testing at Spadeadam will conclude by June 2016. Even larger-scale, controlled testing in the natural environment may subsequently take place. 鈥淲e are considering a number of locations,鈥� Ahmad said.

The aim

The ultimate goal, as with many DNV GL-led JIPs, is the publication of a recommended practice or industry standard. 鈥淭he evolution of best practice, based on a sound understanding of the consequences of underwater releases, will greatly help the nascent CCUS industry to build public confidence and assist the rollout out of a vital carbon abatement technology,鈥� Cooper said.

鈥淚t will be valuable for risk assessment,鈥� Ahmad added. 鈥淭his sometimes requires adjustments to the assumptions of computer models for gas dispersion, and for that you need data from experiments on this scale. The contribution of data from Spadeadam to improving risk models will be the main input to developing safety guidelines for offshore CO₂ 辫颈辫别濒颈苍别蝉.鈥�

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