The Dorado Development Offshore Project Proposal (OPP) describes how Santos WA Northwest Pty Ltd (Santos) proposes to develop petroleum resources in the Dorado field contained in the Bedout Sub-basin, located in Commonwealth waters approximately 140 km offshore from Port Hedland, Western Australia. The oil resources that will be developed lie within petroleum titles WA-437-P and WA-438-P.
Water depths in the Project Area range between approximately 70 and 120 m. Santos commissioned a range of environmental studies to better understand the existing environment within and surrounding the Project Area. Results of these studies supported the assessment of environmental impacts and risks detailed in the Dorado (OPP).
The Dorado Phase 1 Development, which is the subject of the Dorado OPP, will extract the oil resources of the Dorado field and will require gas reinjection to enhance oil recovery. There is potential for a second phase of development to recover and export the gas and should this progress (Phase 2), however this phase would require separate assessment under environment regulatory approval processes, including a separate OPP, if considered commercially and technically viable.
Phase 1 of the Dorado Development will produce oil from the Dorado field and potentially from future tiebacks. Dorado Phase 1 will be designed for liquid handling rates of 100 thousand standard barrels per day (KSTB/d) and gas reinjection capacity of 235 million standard cubic feet per day (MMscf/d). The OPP for Dorado Phase 1 includes potential for up to two (2) future tiebacks (noting that all prospects have not yet been appraised) within the Project Area to augment Dorado field oil production. These tiebacks would connect to the Dorado WHP or FPSO. With provision of up to two (2) future tiebacks, Dorado Phase 1 development could export a volume of up to 350 million barrels (MMbbl) of liquids over 20 years, commencing as early as 2027.
Dorado Phase 1 development will consist of:
• a not normally manned wellhead platform (WHP) with up to sixteen wells (16) (production and gas injection);
• a floating production, storage and offloading (FPSO) facility located in the Dorado field moored by a DTM system used for processing and treatment of the recovered liquids for export, reservoir gas for power generation, pilot flare and gas reinjection;
• initially two subsea hydrocarbon production flowlines, one gas reinjection flowline, risers and an umbilical between the WHP and the FPSO facility; and
• potential for up to two (2) future tie-backs, inclusive of up to 22 wells (including both production and gas reinjection), up to two (2) not normally manned WHP’s, with corresponding future tie-back pipelines and subsea systems including manifolds for these additional WHPs.
All planned petroleum activities, including the future tiebacks, will take place within the Project Area defined for the Dorado Development and will include:
• site surveys;
• drilling;
• vertical seismic profiling (drilling and 3-D);
• construction and installation;
• commissioning;
• operations and facilities maintenance; and
• decommissioning of infrastructure and plug and abandonment of wells.
The Dorado Phase 1 infrastructure will be decommissioned at the end of the commercial life of the project in accordance with legislative requirements.
As has been outlined in NOPSEMA’s Statement of Reasons for acceptance of the project, prior to activities that are part of the Dorado Development commencing, Santos will be required to submit environment plan(s) for petroleum activities that form part of the project that demonstrate that the environmental impacts and risks of the project will be reduced to as low as reasonably practicable (ALARP) and are of an acceptable level. This includes environmental impacts and risks for both planned activities and unplanned events to all parts of the environment as defined in the environment regulations i.e., social, economic, and cultural features of ecosystems including people and communities, natural and physical resources, and the qualities, characteristics and heritage values of locations, places and areas.
Santos will also be required to undertake relevant persons consultation in the preparation of the environment plan(s). Depending on the specific circumstances of each environment plan and petroleum activity, assessment of the impacts and risks identified and evaluated in the environment plans may also need to include consideration of the impacts and risks from scope 3 greenhouse gas emissions within the context of contemporary science, relevant laws and policies.