Northern Gas Pipeline, Queensland, Australia

Northern Gas Pipeline

Northern Gas Pipeline,earlier known as North East Gas Interconnector, is a new 622km underground pipeline developed by Australian energy company Jemena. The new pipeline will connect Tennant Creek in the Northern Territory, to Mount Isa in Queensland.

Jemena was chosen by the Northern Territory government to develop the $800m pipeline in November 2015. The pipeline will have a capacity of 92TJ/d and is expected to be in service by 2018. It will connect the Northern Territory with the gas grid of the eastern states.

"The 622km high-pressure pipeline will be made of steel with a diameter of 14in and a thickness of 6.4mm."

Construction of the new pipeline is expected to enable the commercial exploration and development of existing untapped gas reserves in the Northern Territory. The project is anticipated to generate 600 jobs during construction.

Northern gas pipeline design and route

The 622km high-pressure pipeline will be made of steel with a diameter of 14in and a thickness of 6.4mm. Approximately 457km of pipeline will be located in Northern Territory, with the remaining 165km being located in Queensland. The maximum allowable operating pressure of the pipeline will be 15,320kpa, with a design life of 30 years.

The pipeline runs parallel to the Barkly Highway through sparsely populated areas and aboriginal land. Jemena considered a range of factors during the planning of the pipeline route, including ease of construction, geotechnical factors, regulatory issues and minimisation of environmental impact.

The entire pipeline will have external anti-corrosion coating to protect it from the external environment during its expected lifespan. The primary coating for the pipeline will include an external layer of dual-layer fusion-bonded epoxy anti-corrosion coating.

Secondary protection in the form of a current cathodic protection system will be provided and will consist of cathodic protection stations located at various intervals along the pipeline route.

Infrastructure for Jemena's new pipeline

Associated infrastructure for the pipeline will include a gas processing facility and two compressor stations at Warrego and Mount Isa. The compressor station at Warrego will be known as Phillip Creek and cover an area of 9ha. It will include an inlet metering station and nitrogen separation facilities.

The delivery station at Mount Isa will also cover 9ha and feature an offtake meter station. Three main line valves will be located along the pipeline, in addition to five cathodic protection stations.

Main line valves will isolate the segments of the pipeline for maintenance, operation and repair. Each main line valve will include an automated mainline valve, pipeline blowdown vent, remote terminal unit, solar power supply, cathodic protection unit and offtakes for future compression.

The construction will require approximately 35,000 individual 19m-long sections. The first section was coated in June 2016.

Pipeline construction

Temporary facilities, including accommodation camps, access tracks, works areas and water supply bores will be constructed during the construction phase. The construction will be undertaken within a 30m-wide section of the right-of-way (ROW).

Survey works were carried out along the pipeline route in the Northern Territory and Queensland in mid-2016. Construction is scheduled to start in the second half of 2017.

Contractors involved with the Australian pipeline

Jemena has selected McConnell Dowell to construct the pipeline and associated facilities under a $300m contract.

The pipeline was designed by GPA Engineering, while KBR was responsible for the facility design. Local environmental consultancy EcOz provided environmental consultation services, while Maloney Field Services provided land access and valuation services.

MRC Global Coated is the pipeline supplier for the project. Intertek will inspect the pipeline and Enscope will provide project management services for the natural gas treatment and compression facilities.

Synertec was contracted to design, supply and commission the process control and safety system for Northern Gas Pipeline (NGP) in December 2016.