An estimated 3,000 km of pipeline is planned offshore Australia over the next ten years, costing more than $15 billion, with about 30 per cent of this cost relating to stabilisation measures.
In Australia, pipeline stability is uniquely challenging due to the onerous metocean and seabed conditions, and the prevalence of light gas pipelines.
Against this background, it has been recognised that current design approaches are flawed because they neglect the potential benefits of seabed mobility.
This mobility, for example through scour, changes the topography and strength of the seabed.
If scour holes form around a pipeline, the hydrodynamic lift is reduced and the soil support is altered.
The pipe may sag into the scour hole, and as the scour holes spread along a pipeline, self-burial may occur.
The O-Tube Program
To turn these qualitative observations into quantitative design practice, the O-Tube Program was initiated by a partnership between the University of Western Australia, Woodside, Chevron, Wood Group Kenny and Atteris, with support from the Australian Research Council.
The O-Tube Program is part of the broader STABLEpipe joint industry project (JIP), which is focused on improving the design of subsea pipelines and targeting the multi-billion dollar stabilisation costs associated with Australia’s planned oil and gas projects.
How the O-Tube facility works
The O-Tube facility is a huge closed-loop flume with a base of natural seabed soil.
It contains 60 tonnes of water which can be rapidly circulated under precise control.
Experiments in the O-Tube provide observations of seabed behaviour during cyclones which could not otherwise be made, as well as data on the loading of infrastructure such as pipelines.
For example, the O-Tube experiments allow direct measurement of the pressures applied to a pipeline by cyclonic waves with up to 1 in 1,000 year return periods.
Meanwhile, the changing topography of the seabed is a captured by digital imaging methods, including binocular infra-red scanning.
This new ability to quantify cyclonic seabed interactions in detail has allowed new theoretical methods for predicting seabed morphology to be developed.
Once calibrated against the O-Tube results, these methods then provide a basis to optimise the design of seabed pipelines and other offshore infrastructure.
An in-house technical team led by Winthrop Professor Liang Cheng from the School of Civil, Environmental and Mining Engineering, and Winthrop Professor David White from the Centre for Offshore Foundation Systems, conceived, designed and built the O-Tube facility using world-leading control and data acquisition technology.
Program outcomes
These O-Tube observations have led to improved analysis methods that have fed directly into local gas projects, leading to improved design and significant project cost savings, including the life extension of the trunkline from the North West Shelf Venture gas plant, located on the Burrup Peninsula in the Pilbara region of Western Australia, to the offshore North Rankin A platform, located offshore approximately 135 km north-west of Karratha.
The observations are also being used to develop new stability design approaches for adoption in international design codes.
Woodside Senior Vice President of Health, Safety, Environment and Technology Shaun Gregory said that by working together, the project partners had been able to significantly improve the future design of offshore oil and gas pipelines.
“This is a practical example of how embracing technology can achieve real cost savings for oil and gas companies,” said Mr Gregory.
Chevron Australia Asset Development Manager Gerry Flaherty said the project was helping to give the industry a better understanding of pipeline reliability and helping to reduce stabilisation costs for subsea pipeline owners.
The O-Tube had been used for studies to optimise pipeline design for Chevron’s Wheatstone Project, providing significant savings.
Awards
In February 2014 the O-Tube Program won the Australasian Industrial Research Group (AIRG) Medal for Australasian Major Industry Technological Innovation.
The AIRG presented the medal, saying the cutting edge O-Tube Program had allowed for significantly improved designs of offshore oil and gas pipelines while ensuring cost savings for the Australian offshore oil and gas industry.
“It is a great demonstration of industry-academia collaboration with successful translation of the research outcomes,” said AIRG President Leonie Walsh.
For more information contact Professor David White from the Centre for Offshore Foundation Systems at david.white@uwa.edu.au.