DECOMMISSIONING
THE DECOMMISSIONING PROCESS
Image Showing Helix Q7000 Heavy Well Intervention Vessel.
The Q7000 is working on our decommissioning project at the Basker Manta Gummy fields in 2024
WHAT AND WHERE ARE WE DECOMMISSIONING?
Basker Manta Gummy (BMG) is a legacy facility previously owned and operated by ROC Oil. There are seven wells, auxiliary structures, and a network of around 22 km of flowlines and umbilicals. We plan to commence decommissioning the remaining BMG subsea facilities during Q3 2023. The decommissioning works will comprise two phases. Phase 1 (2023 – 2024) of decommissioning at BMG will:
Prepare the facilities for decommissioning through cleaning and flushing activities.
Safely install cement plugs deep inside the offshore wells to permanently seal them by the end of 2023.
Remove subsea structures from the seabed; this aspect may be completed in Phase 2.
Cut and recover a steel pile and casing from +/- 1m below the seabed; we anticipate leaving the remaining steel and concrete below the seabed.
Complete seabed/debris surveys.
This scope requires a Heavy Well Intervention Vessel and one or more support vessels. We will use the Helix Q7000; the vessel and crew will operate inside the BMG Field for approximately 120 days (24/7). Support vessels will also operate in the field and will re-provision the Helix Q7000 with food, fuel, and equipment. The vessels will also transport equipment and waste back to shore, transiting between BMG and Barry Beach or an alternate port in the region.
Phase 2 ( 2024-2026) of decommissioning will deal with removing any remaining structures and, as a base case, removing all flowlines and umbilicals, leaving a clear seabed. Phase 2 will use one or more construction support vessels to remove lines. The flowline removal activities are expected to take approximately 50 days on a 24 hours per day basis and include inspection and monitoring. campaigns. The window for this activity is 2024-2026, with the possibility of follow-up inspection and monitoring.
CURRENT STATE
Timing: 2011 - Present
What you can see here is an illustration of the infrastructure currently in the BMG field, including subsea production wells, flowlines, control umbilicals and a Manifold. Though no oil is being produced by these facilities, they are still playing a role in ensuring oil remains contained.
Marine life interacts with oil and gas equipment on the seabed. In 2020 we commissioned a habitat study of the BMG facilities to understand how marine life has been interacting with the facilities over time. Check out this video to see what's under the sea @ BMG.
PHASE 1
Status: Consultation complete-Environment Plan accepted by NOPSEMA
Timing: 2023/2024
In Phase 1 the wells will be permanently sealed with cement, and well equipment such as the production trees and manifold shall be removed. We will come back to pick up the flowlines and umbilicals. It is planned to retain the Petroleum Safety Zone until then.
Take a look at this video for more information on what a Petroleum Safety Zone is and what that might mean for you.
PHASE 2
Status: Consultation complete-Environment Plan accepted by NOPSEMA
Timing: Between 2025 and end 2026
In Phase 2 we will recover the flowlines and umbilicals from the seabed. We will undertake debris clearance surveys to confirm the status of the seabed. The only things remaining will be the steel and concrete of the wells and manifold pile below the surface of the seabed. These are installed deep into the seabed and cannot be recovered.
ENVIRONMENTAL IMPACTS AND RISKS
What are they?
During our project planning for BMG decommissioning we have taken time to understand the interactions with the environment and possible outcomes. Each of the impacts and risks have been evaluated. Following evaluation, which involves characterizing the level of impact and risk, we identify control measures to reduce the risks to the environment to as low as reasonably practicable, and to an acceptable level.
We are sharing this information to allow consultees to reflect on their own functions, interests and activities and consider whether the interactions between our activities and the environment are relevant to them, and to begin a two-way conversation to learn more about those overlaps and potential opportunities to further reduce the impact, or risk.
Planned Activities
The decommissioning process includes a range of interactions within the environment. These result from:
Physical presence of the facilities and the vessels we will use to decommission them
Seabed disturbance
Light emissions from vessels
Underwater sound emissions from vessel propellers and subsea equipment such as multibeam echo sounders.
Atmospheric emissions from fuel use and flaring of excess reservoir hydrocarbons
Planned discharges - subsea operational
Planned discharges - surface operational
Planned discharges - routine vessel
Details of these activities, and how we manage our activities to reduce impacts, can be found in the Environment Plans section 6.
Risk events (scenarios)
Marine fauna interaction with vessels causing disturbance or injury to the animal
Introduction, establishment and spread of invasive marine species from vessels
Dropped objects disturbing the seabed
Waste contaminating the environment (hazardous and non-hazardous)
Small leaks or spills of chemicals or hydrocarbons
Emergency Situations
Loss of containment of diesel from vessel fuel tank
Loss of well control resulting escape of hydrocarbons from the reservoir
Details of these risk events can be found in section 7 of the Environment Plans. The section characterizes the risk events, and describes how we manage our activities to prevent the risk events from occurring, and, in the unlikely event they do occur, how we would respond.
HOW DO WE MANAGE ENVIRONMENTAL IMPACTS AND RISKS?
BMG DECOMMISSIONING PLANNED ACTIVITIES
Potential Impact: Displacement of Other Marine Users due to vessel operations and associated exclusion and safety zones. Management and mitigation includes: Engagement with other marine users. Notification before the start of activities and ongoing communication will provide information to other marine users. Vessel will follow marine requirements for safe navigation and radio equipment. Lay down of equipment on the seabed will only take place within the designated safety zones. Debris surveys to confirm clear seabed. Fisheries damages protocol to facilitate compensation in case of damage to fishing equipment outside of designated safety zones.
Light Emissions: Emissions will be reduced by following legislation and marine orders, through choices of equipment and appropriate fluids handling and well returns management .
Atmospheric Emissions : Emissions will be reduced through following AMSA discharge standards and meeting legislative requirements. A planned maintenance system, fluids handling and a well returns management along with choices of efficient equipment will also reduce emissions. Where CO2 emissions generated during the offshore campaign cannot be eliminated, they will be offset.
Routine vessel discharges: Planned maintenance systems will be in place onboard vessels with AMSA discharge standards complied with to ensure changes to water quality are minimised.
Seabed disturbance: Minimal disturbance will be possible through using positioning technology to accurately place equipment on the seabed, by not storing equipment on the seabed outside of the safety zone, and by managing and monitoring mooring. Critical vessel equipment will be maintained through a planned maintenance system. Following activities the fisheries and damages protocol will be followed and seabed surveys will be completed.
Planned discharges: A Chemical Assessment Process, based on the internationally recognised UKCS Offshore Chemical Notification Scheme will be followed to select chemicals; through this process we investigate chemical ecotoxicity and preference chemicals with lower overall ecotoxicity profiles. Water recovered from the subsea system will be treated to a minimum 30ppm oil in water prior to discharge.
Underwater sound emissions: Noise modelling and vessel noise characterization are completed during planning. The major campaign to seal the subsea wells has been scheduled to avoid sensitive periods for blue whales; the entire Gippsland region is a possible foraging area for the species. For all activities, operational controls will be implemented to reduce noise generation and an adaptive management plan will be implemented which describes how we monitor for whales, and how we respond to prevent disturbance to endangered species undertaking important behaviours such as foraging.
For more details on the control measures please see Sections 6, 8 and 9 of the EP.
BMG DECOMMISSIONING RISK EVENTS (SCENARIOS)
Risk Event: Marine Fauna Interaction: To reduce the risk of interaction with whales the EPBC regulations will be followed. The standard EPBC caution zone will be extended to 500m between whales and project vessels to further reduce risk of injury.
Waste contamination of the environment (Hazardous and Non-hazardous): Vessels will follow the AMSA discharge standards and implement a garbage management plan. Records will be maintained of waste generated and how it was managed.
Dropped object disturbing seabed: Equipment deployment and recovery procedures will be implemented ensuring the lifts are within the safe parameters of the vessel and lifting equipment capability. An as-left seabed survey will be undertaken to confirm the seabed is clear.
Spill or leak of chemicals or hydrocarbons: The vessel will be compliant with MARPOL Annex I (Pollution Prevention Control) and a planned maintenance system will be implemented which ensures equipment is fit for service.
Introduction, establishment and spread of invasive marine species (IMS): The Cooper Energy IMS risk management protocol will be followed with an IMS risk assessment undertaken. This protocol has been designed to operationalise government biofouling management guidelines.
BMG DECOMMISSIONING EMERGENCY SITUATIONS
Loss of containment - Vessel collision : Exclusion and caution zones will be in place with ongoing consultation with marine users. Marine orders and MARPOL requirements will be complied with. Other measures will include implementation of an accepted safety case, planned maintenance system and a SIMOPS procedure. Readiness for an unplanned spill is coordinated through the vessel Shipboard Marine Pollution Emergency Plan, project Oil Pollution Emergency Plan (OPEP) and Operational Scientific Monitoring Plan (OSMP).
Loss of well control: The Cooper Energy Management System ensures well activities are planned and executed in accordance with accepted technical standards. The application of these standards is described within a Well Operations Management Plan. This plan is reviewed by NOPSEMA; the activity cannot proceed unless NOPSEMA find the plan acceptable. In the unlikely event of a release, we have contingency plans including a Source Control Emergency Plan (SCERP), Oil Pollution Emergency Plan (OPEP) and Operational and Scientific Monitoring Plan.
Details of these activities can be found in the Environment Plan section 6 and 7. The Oil Pollution Emergency Plan developed for response preparedness is also available with the EP on the NOPSEMA website.
WHAT WILL HAPPEN TO ALL THE MATERIALS RECOVERED DURING DECOMMISSIONING?
In short, we apply the waste hierarchy. When we recover something from the seabed we will look for opportunities to safely reuse the equipment, repurpose it, or recycle the raw materials. Recovered liquids will be treated at licensed facilities.
The image here shows recovery of subsea equipment from the seabed during an offshore campaign in 2021 to an offshore construction vessel. The vessel was equipped with a large crane and remotely operated vehicle to help collect and recover the equipment. The recovered equipment was processed in Australia. Our project contractors were able to repurpose or recycle over 90% of the materials we recovered from offshore.
Our intent is to manage recovered materials within Australia, and to utilise the nations growing circular economy. We will be exploring opportunities for this with specialist waste management companies as we plan and execute the offshore campaigns.
GIPPSLAND ACTIVITIES SPILL RISK
Spill risk scenarios for our Gippsland offshore facilities and activities include loss of hydrocarbon inventory from facilities and loss of fuel inventory from vessels undertaking work for us offshore.
This set of images are based on spill modelling undertaken during the preparation of the BMG Closure Project (Phase 1) Environment Plan and Oil Pollution Emergency Plan. These plans provide for our upcoming decommissioning work at the offshore BMG facilities.
HOW MUCH OIL COULD END UP ON SHORELINES?
Within this image, the different colour lines indicate the varying degrees of oiling which could occur along coastlines in an emergency blowout scenario. This assumes no intervention- that is that we do nothing to respond which is not what would happen in reality. The line colour indicates the maximum level of oiling which could occur at shoreline locations inside the line. Oil would also occur within and on the water; we have detailed maps for all phases of the oil within the Environment Plan and modelling reports within the appendices.
IN THE EVENT OF A SPILL, HOW LONG WOULD IT TAKE FOR OIL TO REACH THE SHORE?
The lines in this image delineate the time oil takes to reach the shoreline in an emergency blowout scenario. It assumes no intervention. The time taken for oil to reach the shoreline generally increases with distance from the well. The longer oil spends at sea the more weathered it becomes. Oil in the BMG reservoirs has a high proportion of wax. If spilled, this can remain in the environment for extended periods, and be transported long distances.
CONTACT US
We invite you to join our network and engage with us regarding our activities.
To find out more about Cooper Energy or our activities please contact us through the webform. We are keen to hear from people and organisations with functions, activities or interests within the areas we operate and to discuss how we interact and find out how we can work together.
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Page last updated April 2023
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