Pipeline networks support depleting production According to AEMO’s recently released Gas Statement of Opportunities, gas production in south-east Australia is expected to decline from 2023. A number of existing gas fields in south-east Australia are expected to reach their end of life between mid-2023 and mid-2024.
The expected depletion of the Esso Australia and BHP joint venture, the Gippsland Basin Joint Venture (GBJV), in 2024 is expected to lower the available Gippsland supply from 260 PJ in 2023to 201 PJ in 2024. While there are several anticipated projects which could improve the supply, with the majority located in the Otway Basin, they could be constrained by the capacity of the South West Pipeline (SWP) and supply issues would not be resolved without an expansion of the SWP. Therefore, most fields in the Otway Basin could cease production unless development plans and plant modifications proceed. Even though the GBJV’s West Barracoota gas development in the Bass Strait, Victoria is on track for a 2021 start-up, AEMO’s forecast of a gas shortfall takes this development into account.
Several gas development and appraisal programs in the region have also been deferred recently. According to a statement by 3D Oil Limited on 11 June, in the Otway Basin, Beach Energy has deferred its plans for the drilling of the Aritsan-1 exploration well as well as a number of near-field and appraisal wells at Thylacine and Geographe until at least the next financial year. “These variables underpin the prediction that long-term gas supply in south-east Australia is under threat,” 3D Oil stated. It is predicted that current reserves and contingent resources in southern states will be insufficient to offset the decline of production.While COVID-19 has seen reductions in demand, it is expected to be short-term and the deferral of gas exploration and development in south-east Australia will exacerbate the looming supply shortfall.
While there are some local projects that are expected to support the demand, the recent increase in pipeline networks are helping to sustain the eastern states. An example of this is the Eastern Gas Pipeline (EGP) which supplies more than half the gas consumed in New South Wales. Jemena hopes to further increase the supply by connecting the EGP to a LNG import terminal at Port Kembla. Jemena recently submitted plans which would enable new gas from Port Kembla to reach areas of demand in Victoria and New South Wales. Another new pipeline is the Northern Gas Pipeline (NGP), commissioned in 2019, which spans between the Northern Territory and Queensland.
The pipeline enables gas resources from the Timor Sea and onshore gasfields in the Beetaloo Basin and Central Australia to be transported to customers between Adelaide and Brisbane as well as regional areas. The pipeline will initially deliver around 90TJs of natural gas each day, which is around 6 per cent of eastern Australia’s average daily gas use. Recently, talks of a $6 billion trans-Australia pipeline linking large gas fields off Western Australia to the east coast have risen again through the Neville Power-led National COVID-19 Co-ordination Commission, but there are still serious doubts about the financial feasibility of the project.
Even prior to the new projects being commissioned, Australia had a significant number of transmission pipelines. Some examples include the 1 0km Wheatstone Ashburton West Pipeline which links the Wheatstone domestic gas plant to the Dampier Bunbury Natural Gas Pipeline; the 627 km Queensland Gas Pipeline which links the Wallumbilla gas hub in south-central Queensland to large industrial gas users in Gladstone and Rockhampton; and the 292 km Darling Downs Pipeline which links the Wallumbilla gas hub near Roma with the Talinga gas plant near Chinchilla and Jemena’s Darling Downs gas-fired power station near Dalby in Queensland.
With a continuing growing network of pipelines in Australia, the importance of inspection, monitoring, maintenance, and repair of well-developed and new assets is also on the rise. The potential risk involved if these critical assets were to be damaged (for example as a result of corrosion -internal or external, excavation, natural force, equipment failure, material/weld failure, incorrect operation etc.) is well known and could result in ecological disaster, human casualties and financial loss. Maintenance of new and old assets Pipeline maintenance is a critical element for existing assets, both for new and established ones, which is why pipelines are inspected on a regular basis.
Pipeline operators may utilise a number of methods to do this. Visual methods can include the more traditional means of having experienced personnel to walk along the pipeline route to identify cracks and other noticeable defects, but efficiencies can be gained through the use of unmanned aerial vehicles (UAVs or drones). Pigging is an in-line inspection technique in which devices, generally referred to as ‘pigs’, are inserted into pipelines to perform various maintenance operations. This is achieved without stopping the flow of the product in the pipeline. Intelligent pigging is an inspection technique whereby an inspection probe, commonly referred to as a ‘smart’ pig, is propelled through a pipeline while collecting critical data, such as the presence and location of corrosion or other irregularities on the inner walls of the pipe. Smart pigs are capable of performing advanced inspection activities as they travel along the pipe, in addition to just cleaning it.If an in-line inspection detects an abnormality, operators will conduct an integrity dig to take a closer look and repair if needed.
Repairing aging assets among other factors, the age of pipelines can cause significant risks when it comes to deterioration, which is why repairs of these assets are crucial. The 440km Roma to Brisbane pipeline came into operation in 1969 and is Australia’s oldest natural gas pipeline. While this and some of Australia’s other older pipelines are aging, the country still has a good safety record and has never seen a major gas outage caused by a pipeline incident. However, some of the country’s existing pipeline infrastructure was built using materials that are no longer used today. Coating materials, for example, have significantly improved compared to those used decades ago. As the nation continues to increase its demands for energy transportation, investment in infrastructure upgrades—including aging pipelines—is a necessity to continue moving products safely and with minimal failure incidents. As pipelines age, there are a number of important considerations which must be factored into determining a suitable pipeline repair technique. Defect location (internal or external), defect severity (severe or normal) and the type of repair (temporary or permanent) are just a few. Another important factor is to find a method which allows operators to perform repairs on ‘live’ assets in order to prevent downtime, contain or reduce operating expenditure, as well as minimising customer service disruptions. Temporary repairs are typically only used in urgent or emergency situations and in preparation for a permanent arrangement. For permanent repairs, several methods are currently being used and many are becoming increasingly advanced. Some of these methods include pipe grinding and recoating, steel reinforcement sleeve repair, composite wrap repair and hot tap.
Pipe grinding is used to produce smooth surface and remove the harmful stress concentration of defects and micro-cracks. Steel reinforcing sleeves consist of two halves of a steel cylinder which are placed around the pipe and welded to fully encircle the damaged section and restore the strength of the pipe. A wide variety of composite materials are used in pipeline repair systems. They mainly consist of glass or carbon fibre reinforcement in a thermoset polymer matrix. The method is suitable for non-leaking defects such as pits, dents, gouges, and external corrosion. Hot-tapping allows the pipeline to stay in service, however it requires testing and welding inspections similar to pipe replacement.
No matter what method is used to repair existing pipelines, operators need to ensure the repair is implemented safely to minimise environmental impact and to reduce the interruptions of the service. In Australia, the design, construction, testing, operations and maintenance of high-pressure gas transmission pipelines made of steel are underpinned by Australian Standard 2885.
Sources: Pipeline Facts and Figures, APGA; 3D Oil completes farm out of T/49P to Conoco Phillips Australia, 11 June 2020, 3D Oil Limited; Cost-efficient fixes with zero downtime, DNV GL; Recent Advances in Pipeline Monitoring and Oil Leakage Detection Technologies: Principles and Approaches, Mutiu Adesina Adegboye et al.; Repair Techniques for In Service and Out of Service Buried Pipelines, Aftab A Haider; Composite Wrap for Non-Leaking Pipeline Defects, United States Environment Protection Agency; What pipeline companies are doing to keep their operations safe, Canadian Energy Pipeline Association
