The first commercial gas discovery was made at the Gidgealpa field in 1963, followed by the first Permian oil discovery at the Tirrawarra field in 1970 and the first Jurassic oil discovery at the Strezlecki field in 1978. Today, the Cooper Basin contains over 150 gas fields and more than 70 oil fields that contain over 900 producing oil and gas wells.

Supporting the production of these assets is a network of pipelines that transport oil and gas from wellheads to satellite stations and onto the processing plants at Moomba and Ballera for transport via transmission pipelines to market.

Santos’ Cooper Basin acreage and main transmission pipelines are shown in Figure 1. The company has been supplying sales gas to Adelaide, via the Moomba to Adelaide Pipeline and Sydney, via the Moomba to Sydney Pipeline, since 1969 and 1976 respectively. Further to these original markets, Santos provides ethane to Sydney and sales gas to Brisbane and Mt Isa.

In the Cooper Basin, there are over 3,000 oil and gas pipelines. These include 80 major export/trunklines (between 250 mm and 750 mm in diameter), over 330 gathering lines (between 150 mm and 250 mm in diameter) and more than 2,600 flowlines (between 60 mm and 150 mm in diameter). The pipeline network is extremely complex with pipeline lengths from 50 m up to 500 km, diameters from 2 inches to 30 inches, a range of coating types including flake shield, tape wrap and fusion bonded epoxy, with pipeline materials ranging from carbon steel to glass reinforced epoxy.

Ensuring integrity

To manage the complex Cooper Basin pipeline network, Santos has developed a pipeline integrity management strategy, which includes a number of policies and standards to manage the integrity of its pipelines in accordance with the Australian legislation and standards.

Santos operates its pipeline network in accordance to its Statement of Environmental Objectives (SEO), which has been prepared to ensure Santos meets the requirements of the South Australian Petroleum Act 2000 and specific regulations of the Petroleum Regulations 2000.

To ensure compliance, Santos has developed a number of policies, procedures and environmental, health safety and sustainability (EHS&S) standards. The asset integrity management system (AIMS) has been developed to provide a structured framework for integrity management and measures statutory and corporate conformance to the Santos environment, health and safety managment system standards.

The pipeline asset management system (PAMS) has been developed to provide an effective and efficient means of managing the safe and reliable operation of all pipelines and ensuring compliance with statutory requirements. The objective of PAMS is to manage the design, construction, testing, ongoing operation and maintenance, integrity and corrosion management, mothballing and abandonment of pipelines. An integral part to PAMS is assessing the EHS&S consequence of pipeline incidents.

PAMS uses a risk directed asset management (RDAM) philosophy with the aim to optimise the life cycle of its assets’ fitness for purpose in a cost effective manner. This system is driven by a risk assessment process, in accordance with AS2885, which provides the means by which hazard levels are regularly assessed throughout the life of the asset against the types of failure and likelihood of such a failure type occurring.

Once the risk level has been quantified, according to EHS&S standards, the suitable level and frequency of integrity monitoring, mitigation and inspection methods is determined. The overall objective of the RDAM of pipelines process is to produce an integrity management plan (IMP) for each pipeline that outlines the activities required to ensure that the pipeline has a suitable level of protection against premature failure.

In summary, Santos manages the integrity of its pipeline network to ensure compliance with the various standards, Australian legislation and acts to ensure that the risks to continual pipeline operation are ‘as low as reasonably practicable’ (ALARP).

Each pipeline IMP specifies the suitable monitoring, mitigation and inspection activities.

Mitigation applies to any activity that prevents deterioration due to the corrosive environment the pipeline is exposed to and includes the following:

• Chemical injector checks
• Transformer rectifier checks
• Pipeline batch treatments
• Pig barrel treatments
• Pigging runs.

Monitoring applies to any activity that provides short-term information to modify mitigation activities and includes the following:

• Gas well water sampling
• Pig trash sampling.

Inspection applies to any activity that provides long-term information to modify mitigation activities and includes the following:

• In-line inspections
• Direct assessments
• Pig barrel inspections
• Lease spool inspections
• Below and above ground right-of-way inspections.

Most of these IMP activities are performed in the field by the PAMS Technicians. Once these activities have been carried out all records are captured in the Pipeline Information Management System (PIMS) database. This information is then measured on a monthly basis through rigorous key performance indicators (KPIs) and quarterly KPI reviews with the field asset owners and Santos management. The data in PIMS is interrogated to assess each pipelines risk level and the IMP activities are moderated to redirect target pipeline risk level to ALARP.

IMP information is continually reviewed and the results are then fed into the development of a five year plan that provides a planning tool for optimisation of IMP frequencies, budgeting and ensuring suitable resource levels..

Pipeline integrity at Santos has a number of future challenges going forward in terms of managing an ageing network, investigating the use of new technologies such as remote chemical monitoring and new inspection techniques, dealing with higher carbon dioxide producing wells and ongoing management of bacterial corrosion.