Wheatstone Nearshore Exit Pit Detailed Design

Atteris employed in-house shore crossing expertise to complete the detailed design of the Wheatstone nearshore micro-tunnel exit pit. Qualitative erosion assessments demonstrated erosion mitigation measures recommended by the contractor were not required. This reduced the CAPEX of the shore crossing.

The Wheatstone Development is located 225 km north of Onslow, WA, in 72 m water depth. Gas and condensate from the Wheatstone and Iago fields is transported to an LNG facility via a 44-inch trunkline. The Trunkline is housed in a 2 m diameter and 1.3 km long concrete tunnel at the shore crossing. The tunnel was terminated in a pre dredged and sand backfilled exit pit. The original shore crossing design by the construction contractor envisaged using graded rock as an erosion mitigation technique for the exit pit. This was flagged as a pipeline integrity risk during installation that required further investigation into the possibility for removal or substitution. Atteris was engaged to perform the detailed design of the exit pit, with the goal of optimising the design and removing the requirement for graded rock as an erosion mitigation measure.