Beach Energy (Operations) Limited, a subsidiary of Australia’s oil and gas player Beach Energy, has submitted an environment plan (EP) to the country’s offshore regulator for geophysical and geotechnical seabed surveys off the coast of Australia.
The National Offshore Petroleum Safety and Environmental Management Authority (NOPSEMA) has confirmed that Beach Energy submitted the environment plan on November 6, 2023, proposing to undertake geophysical and geotechnical seabed surveys within the Otway and Bass basins in Commonwealth waters within licenses: VIC/P43 , VIC/P73 , VIC/L23 , T/L2 , T/L3 , T/L4 , T/30P , T/L1 , T/RL2 , T/RL4 , and T/RL5 .
These seabed surveys are required to inform future plug and abandonment activities of existing legacy suspended wells, drilling of subsea gas wells , and potential tie-ins to connect new gas wells to existing subsea infrastructure, which are outside the scope of this EP. The proposed seabed surveys will be carried out no earlier than February 1, 2024, and no later than December 31, 2028.
The company explains that seabed surveys are estimated to take up to 200 days for the Otway operational area A, 40 days for Otway operational area B, and 120 days for the Bass operational area. The surveys may be done in one campaign or as a number of separate campaigns.
According to Beach Energy, the exact objectives of the seabed surveys are to identify potential seabed debris, obstructions, and hazards that could interfere with the positioning and anchoring of the moored mobile offshore drilling unit (MODU) and subsea infrastructure placement; and to identify and map the nature and distribution of geomorphological features such as canyons, scarps, vents, pinnacles etc. in the operational areas using side scan sonar (SSS) and multi-beam echo sounder (MBES).
Aside from this, the list of objectives for these surveys entails the identification of sub-seabed features and lithology to assist determination of anchor holding capability/limitations and subsea infrastructure locations using sub-bottom profiler (SBP) investigations; accurately measure water depth and mapping seabed topography across the operational areas; and verify the position of existing subsea infrastructure.
In addition, the objectives also cover the collection of seabed core samples to correlate sub-bottom conditions that may have implications for the MODU anchor holding performance and subsea infrastructure placement; conduct an in-situ cone penetrometer test (CPT) to a suitable depth of interest for anchor holding analysis and subsea infrastructure location selection; obtain seabed imagery using a remotely operated underwater vehicle (ROV), autonomous underwater vehicle (AUV) or drop camera; and collect sediment and water samples at representative locations for baseline data.
The geophysical survey methods proposed are multi-beam echo sounder, side scan sonar, sub-bottom profiler, and magnetometer. Line spacing will consist of nominal 100 m spaced primary lines with crosslines spaced at 500 m. The survey will be acquired in two passes to provide seabed depth and image information for anchor positioning. The line spacing will achieve a 20% overlap of adjacent swathes of processed data.
On the other hand, the proposed geotechnical sampling includes cone penetrometer testing and crop coring or vibrocore. In addition, seabed imagery will be taken using a camera placed overboard via a tether and/or by a remotely operated vehicle or autonomous underwater vehicle. Water and sediment samples will also be taken for baseline information. However, seismic surveys are not included in the activity scope.
Furthermore, Beach underlines that a vessel, which will be used to undertake the seabed surveys, will travel at approximately 4–5 knots (7–9 km/hr) when undertaking the geophysical survey and stationery when undertaking the geotechnical sampling. The vessel will hold the station using dynamic positioning (DP) or propellers as water depths are too deep for anchoring. The use of support vessels is not required and vessel refuelling will take place at port.
Beach Energy is working on various growth projects. The firm is now targeting the start of drilling operations at its development well off Taranaki towards the end of the first quarter of 2024. These activities will be carried out with one of Valaris’ heavy-duty modern jack-up rigs.
Meanwhile, Australian Energy Producers recently urged the Commonwealth to fix the broken offshore regulatory system after the logjam of energy supply and carbon capture projects awaiting approval was exposed.
Plans have been tangled up in the approvals process for 562 days on average for exploration and 400 days on average for development as a result of regulatory uncertainty, following a Federal Court ruling last year.