Found by INPEX in 2000, the Ichthys gas and condensate field in the Browse Basin is the largest discovery of hydrocarbon liquids in Australia in 40 years.
Located 220 km off the northwest coast of Western Australia, one of the key components of the project is the 889 km, 1,020 mm diameter export pipeline running from the field to an onshore LNG processing facility located at Blaydin Point on the Middle Arm Peninsular in Darwin. Engineering, procurement, construction and installation of the subsea pipeline was undertaken by international oil and gas contractor Saipem.
Laying the pipe
With construction taking place in the environmentally sensitive Darwin Harbour as well as in deep water off the coast of Western Australia, different vessels were required.
The vessels Saipem chose to lay the pipeline included:
- Two spudded backhoe dredges, two split hopper barges, one survey and one side stone dumping vessel for Darwin Harbour trenching and rock dumping works
- A moored pipelay barge, three anchor handling tugs, two supply vessels, one survey/remotely operated vehicle (ROV) vessel, seven cargo barges and tug combinations and four bulk carriers for shallow water pipeline installation.
- DP3 pipelay vessel, eight pipe supply vessels, eight bulk carriers, one fuel tanker, two supply vessels and one survey/ROV vessel for deep water pipeline installation.
Saipem’s semisubmersible pipelay barge, SEMAC-1, installed the 164 km shallow water section of pipe. This work included laying the first 18 km section of the pipeline through Darwin Harbour in mid-2014.
Saipem’s state-of-the-art deep water installation vessel, Castorone, laid the remaining 718 km of pipe to the Ichthys field.
Constructing a pipeline can be a logistical problem at the best of times, so when there are dozens of construction and support vessels involved challenges can arise.
The main issues identified by INPEX in the laying process were the logistical effort required to maintain pipe supply to the pipe lay vessels to keep up production and the mechanical reliability of the construction equipment on board the pipe lay vessels to ensure efficient production.
Environmental support
The main environmental challenges faced during the construction of the pipeline was the sensitivity of Darwin Harbour, which is a commercial port, but also used extensively by tourism operators and recreational fishermen.
The harbour is well documented as having a distinctive biodiversity, including turtles, dolphins, dugongs, crocodiles and fish, which required particular attention during the early planning stages of the pipe-lay operations.
Engineering solutions and approved management plans were subsequently implemented to minimise the environmental impact during pipe-lay in shallow water and at shore crossings.
Safely does it
A major safety challenge on the project was multiple movements of 75,000 joints of large pipe weighing up to 20 tonnes each.
To protect personnel from injury when safely executing two million pipe lifts to manufacture and coat and install the pipeline, INPEX commissioned automated mobile lifting equipment from the Bredero Shaw coating yards.
Supplied from two pipe mills in Japan and one in Europe, the pipes had to be repeatedly lifted and moved to different inspection, storage and coating application stations.
Covering tracks
Approximately 750,000 tonnes of protective rock was used to cover the 15.4 km of the pipeline through the inner areas of Darwin Harbour, with positioning systems used to manoeuvre the rock to exact locations.
Using quad road trains and local drivers with good knowledge of Darwin and surrounding areas, several hundred thousand tonnes of filter and armour rock was safety and successfully transported from nearby quarries since June 2013, involving about 7,000 round trips and 1,400,000 km of travel.
Final stages
Remaining scope of work after the installation of the pipeline is the flooding and hydro test of the pipeline to prove mechanical completion, then the subsequent dewatering and preservation prior to the introduction of hydrocarbons.
As the pipeline itself nears operations, there are still two major factors to complete the greater Ichthys LNG Project.
These include the towing of the central processing facility and floating production, storage and offloading facility from South Korea to the Ichthys Field; and completion and shipment of the remaining modules to Darwin – 166 of more than 200 have been shipped to date.
First production is expected in the third quarter of 2017.
The Ichthys LNG Project is a joint venture between INPEX (63.445 per cent), TOTAL (30 per cent), CPC (2.625 per cent), Tokyo Gas (1.575 per cent), Osaka Gas (1.2 per cent), Chubu Electric (0.735 per cent) and Toho Gas (0.420 per cent).