WA-61-L and WA-62-L Subsea Infrastructure Installation
|Activity type||Construction and installation of a facility|
|Activity subtypes||Any other petroleum-related activity|
|Submitted by||Woodside Energy Scarborough Pty Ltd|
|Submission date||22 March, 2023|
|Status||Under assessment (with NOPSEMA)|
|Link to previously accepted EP|
Woodside is planning to undertake seabed site surveys and installation of subsea production infrastructure within Permit Areas WA-61-L and WA-62-L, around 374 km west-northwest of Dampier, Western Australia.
A gravimetry survey is planned to be undertaken in Permit Areas WA-61-L and WA-62-L to support Woodside’s knowledge of the Scarborough reservoir. Preparation for the gravimetry surveys involves installation of concrete pads by an LCV. These pads ensure that measurements are acquired at the same position on the seabed in consecutive surveys, such that observed time-lapse differences in gravity and water depth can be attributed to the effect of hydrocarbon production. These pads will remain deployed on the seabed until the end of Scarborough field life. Following preparations, a baseline gravimetry survey will be conducted to monitor pressure and saturation changes in the reservoir to inform decisions regarding reservoir management.
The first subsea installation campaign (Campaign 1) includes pre-and post-lay surveys and the installation of flowlines. Pre- and post-lay surveys will be conducted from a vessel and ROV to assess the seabed condition prior to installation and to confirm the infrastructure location post-installation. Thirteen mud mats are planned to be installed to provide a base for the installation of other infrastructure and up to twelve additional mud mats may be installed as foundations for the Subsea Distribution Units (SDUs) and Umbilical Termination Assemblies (UTAs). Three lengths of flowline, seven In-Line Tees (ILTs) and six Flowline End Terminations (FLETs) which are required for the flow and control of hydrocarbons and produced water to the Scarborough Floating Production Unit (FPU) can then be installed.
The second subsea installation campaign (Campaign 2) includes further pre-and post-lay surveys and the installation of riser, jumpers and umbilicals. Six risers are planned to be lowered to the seabed and connected to the appropriate tie-in structure. It is intended that the risers will be installed pre-filled onshore with treated freshwater. Eight flexible jumpers are intended to be deployed to depth and connected to appropriate infrastructure with ROV support. A total of nine umbilicals, both dynamic and static, are planned to be installed, initiated with an anchor at one end, laid out from there and wet stored on the seabed until connected to associated infrastructure. Following installation, various leak tests will be performed on the installed infrastructure.
The FPU moorings will be installed under this EP, prior to FPU arrival. Moorings and suction piles will be installed by placing suction piles on the seabed and engaging the suction system via a subsea pump, to bury. Attached mooring legs will then be laid back on the seabed in a planned configuration within the future FPU mooring footprint and wet stored until FPU arrival and hook-up.
The cumulative duration of the activities to be undertaken is approximately 18 months, with activities occurring in multiple campaigns for completion within a three-year window.