Liquefied natural gas (LNG)
Shore trunkline microtunnel
Location: Wheatsone Project, Onslow, Western Australia
Project completed: 2014
Applicator/Contractor: Subcon Technologies Pty Ltd, Dredging International Australia
Market sector: Energy
- MasterFlow 871
- MasterFlow 700
Chevron’s Wheatstone Project is a multi-train Liquefied Natural Gas (LNG) and domestic gas plant located on the Pilbara Coast, Western Australia.
The Wheatstone Project involves processing gas from various fields located offshore and the installation of gas gathering, export and processing facilities in water and on land.
The gas is transported to the Wheatstone LNG plant from subsea wells through a trunkline, several kilometers offshore. The last kilometer of the trunkline is sent in from the shoreline through a protective microtunnel.
During tide changes, a grout plug is required inside the tunnel annulus extending 70 metres inside the microtunnel to block water flow.
The challenge was to anchor the last 70 metres of the trunkline within the microtunnel to shore with a precision grout plug.
Since placement of the grout had to be done underwater with low visibility, the team had to develop a new design concept for grout movement, placement and mixing.
A new grout delivery system was designed to overcome some of the challenges. This included a unique trolley system which carried the delivery line and inflatable grout bags down the 70 meter microtunnel underwater.
BASF’s technical services team developed a new high strength non-shrink deep pour precision grout, MasterFlow 871. The grout and water temperature was reduced to 4 degrees Celsius for 48 hours before use, using several refigerated containers. The design of the delivery trolley also assisted temperature control by enabling rapid product placement.
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The Wheatstone Project is located in close proximity to an important whale shark breeding ground, meaning various environmental factors needed to be considered when developing BASF’s grout devlivery system.