Darwin Pipeline Duplication (DPD) Project will enable the delivery of natural gas from the Barossa gas field in the Timor Sea to the existing Darwin Liquified Natural Gas (DLNG) facility in the Northern Territory of Australia.
In August 2022, Australian oil and gas exploration and production company Santos announced the final investment decision (FID) on DPD project as operator of the Barossa joint venture.
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The independent Northern Territory Environment Protection Authority (NT EPA) gave its consent to the development of Darwin Pipeline Duplication Project in January 2024.
Once complete, the pipeline project will stretch Barossa Gas Export Pipeline to the Santos-operated DLNG facility. It will also enable the existing Bayu-Undan to Darwin pipeline to be repurposed for carbon capture and storage (CCS), subject to regulatory approvals.
Darwin Pipeline Duplication Project Route
Around 100km of the DPD Project will be located in Northern Territory jurisdiction. An additional 23km of the pipeline will be in Commonwealth waters.
The DPD Project will run mostly parallel to Santos’ existing Bayu-Undan to Darwin pipeline. However, at two points it will cross over to avoid the Darwin Harbour shipping channel.
The ‘near-duplication’ of the existing pipeline has been identified as the best route to minimise environmental and social impacts.
The proposed project area includes three main sections- Offshore Northern Territory waters including waters beyond the Darwin Harbour Region Management Area as well as the designated spoil disposal site; Darwin Harbour waters; and the shore crossing and onshore segment.
Darwin Pipeline Duplication Construction
The key construction elements of the Darwin Pipeline Duplication Project will include several critical activities.
This will begin with pre-lay trenching and spoil disposal that will involve approximately 12.5km of trenching along the pipeline route in Darwin Harbour, using trenching vessels.
An estimated 255,000m³ of spoil, with a potential maximum of 500,000m³, will be disposed of at an offshore spoil disposal ground.
Pipeline installation will be carried out using an anchored shallow-water pipelay barge for shallow areas, including Darwin Harbour, and a deepwater pipelay vessel. The pipeline will pass via a trenched shore-crossing at the DLNG facility, with supporting structures such as concrete mattresses potentially required in some sections.
Onshore works will include trenching, pipeline installation, and site preparation to facilitate pipe pull and pipeline pre-commissioning within the existing DLNG facility.
Rocks will be installed in certain sections of the pipeline to ensure protection and stability, with temporary rock causeways installed at the DLNG facility to assist with trenching at the shore-crossing.
Pre-commissioning activities will include flushing, cleaning, gauging, and testing of the pipeline, including cleaning, testing, and dewatering from the DLNG facility, with planned dewatering at the pipeline end in Commonwealth waters.
Additionally, vessels will be used for other activities such as trenching, pipelay, rock installation, and general operational support.
The construction activities are expected to be completed over a nominal cumulative period of approximately 15 months in the field.
The carbon-steel pipeline will be protected by a concrete coating. A deepwater pipelay vessel will lay the DPD pipeline on the seabed at a rate of around 2km to 3km per day.
Contractors Involved
Santos contracted offshore pipelay and subsea construction company Allseas for the construction of 123km long, 26-inch/34-inch dual diameter carbon steel export nearshore pipeline.
The scope of works includes engineering and installation of the pipeline; design, fabrication, and installation of 1 off PLET and 1 off ILT; spool fabrication and installation; pipeline trenching and rock protection; mattress installation and span rectification; and pre-commissioning activities.
Allseas will also carry out post-lay and as-built surveys along with landfall site and pipe pull preparations.
In September 2022, Allseas awarded DEME and Van Oord a contract related to the Darwin Pipeline Duplication Project.
Under the contract, the joint venture will support shallow water pipeline installation in Northern Territory waters. This will include trenching, pipe pull operations, rock placement works and preparing the shore crossing at the landfall location.
The project work will see the deployment of a cutter suction dredger, trailing suction hopper dredger and backhoe dredger along with a fallpipe vessel for the rock placement works and a linear pulling winch for the pipe pull.
Canadian materials technology company Shawcor (now known as Mattr) won the contract to provide anti-corrosion, internal flow coat, and concrete weight coatings for the pipeline project. The contract is valued around C$35m.
Mattr will perform the contract works from its Kabil, Indonesia facility.
