Otway Offshore Operations
|Activity type||Operation of a facility for the recovery or processing of petroleum|
Recovery of petroleum using a subsea installation
|Lifecycle Classification||Operation & Production|
|Submitted by||Beach Energy (Operations) Limited|
|Submission date||11 April, 2023|
|Status||Under assessment (with titleholder)|
|Link to previously accepted EP||6731 - Otway Offshore Operations|
Phone: (08) 9110 2180
Beach Energy (Operations) Limited (Beach) is the part owner and nominated operator of the Otway Gas Development. The development consists of offshore and onshore infrastructure necessary for the commercialisation of gas and liquids in the Geographe and Thylacine fields off the coast of Victoria.
Development of the gas fields commenced in 2004 by Woodside Petroleum Ltd under a joint venture arrangement, with first production in mid-2007. Since this date, additional wells have been drilled at the Geographe location (VIC/L23) and the Thylacine location (T/L2) to maintain supply. A further exploration well was drilled in 2021 at the Artisan location (VIC/P43).
The Geographe field located approximately 55 km to the south of Port Campbell and the Thylacine field located a further 15 km south of the Geographe field.
The production wells at the Geographe and Thylacine locations have all been drilled, completed and tied-back to existing infrastructure under separate environment plans (EPs). The Thylacine subsea wells have been commissioned and testing will be performed prior to gas entering the system. The anticipate time for production from these wells is described in section 3.4.
The current offshore operations at Otway are managed under the Otway Offshore Operations EP that was accepted in August 2022 and is valid until 2027 (NOPSEMA Reference 6731).
This EP is a minor amendment to the accepted Otway Offshore Operations EP and an is based on the potential of a 'new or increased environmental impact or risk’ as defined under Regulation 17(6) of the Offshore Petroleum and Greenhouse Gas Storage (Environment) Regulations 2009.
The potential new or increased environmental impacts or risks from the development are:
• Greenhouse Gas Emissions – The currently accepted EP contained emissions forecasting that has been refined since acceptance. These refinements alter the risk assessment assumptions included within the accepted EP. It is, therefore, considered that these may constitute an increased impact to the environment. This has been addressed in Section 6.3.
• Physical disturbance to the seabed – The currently accepted EP does not consider the potential environmental impacts of the subsea flowlines and manifolds associated with the Thylacine wells. These potentially create an increased environmental impact to the seabed. These potential environmental impacts have been assessed in section 6.6 and section 6.7.
• Spill risk – In the unlikely event of a spill, the four subsea wells at Thylacine have the potential for an increased environmental impact. The platform wells at Thylacine were estimated to have a potential spill volume of approximately 28 MMscf/day. The Thylacine subsea wells have an estimated spill volume of 139 MMscf/day. This increased environmental impact has been assessed in section 6.14.
• Planned subsea discharges – The subsea wells at Thylacine may result in additional discharges of hydraulic fluid, dye, mono-ethylene glycol and other chemicals that could have an increased environmental impact. These additional discharges have been included in section 6.9.
The scope of this Environment Plan (EP), is the continued operation, inspection, maintenance, and repair (and associated activities) of the offshore assets associated with the Otway Gas Development:
• Thylacine-A well head platform (x4 production wells).
• Three subsea Geographe production wells (G 2, 4, & 5) and
associated subsea infrastructure.
• Four subsea Thylacine production wells (TN-1, TN-2, TW-1, & TW-
2 and associated subsea infrastructure.
• Four subsea suspended wells (Artisan1, Geographe 1, & 3,
• Otway Pipeline System consisting of two subsea pipelines – Gas
Pipeline and MEG pipeline.