How do you plan and execute subsea pipeline decommissioning and abandonment?

1 Assess the condition and risks

The first step in planning subsea pipeline decommissioning and abandonment is to assess the condition and risks of the pipeline system, including its location, length, diameter, material, coating, contents, pressure, temperature, corrosion, integrity, and potential impacts on the environment and other users of the sea. This assessment will help you determine the most suitable decommissioning and abandonment method, such as leaving the pipeline in place, removing it partially or completely, or filling it with cement or other materials. You will also need to collect and analyze data from inspections, surveys, and monitoring to support your decision.

2 Consult the stakeholders and regulators

The second step in planning subsea pipeline decommissioning and abandonment is to consult the relevant stakeholders and regulators, such as the government authorities, the pipeline owners and operators, the contractors and service providers, the environmental groups, the fishing and shipping industries, and the local communities. You will need to obtain the necessary permits and approvals, comply with the applicable laws and standards, and address any concerns or objections that may arise. You will also need to communicate and coordinate with the stakeholders and regulators throughout the decommissioning and abandonment process, and report on the progress and outcomes.

3 Prepare the equipment and personnel

The third step in planning subsea pipeline decommissioning and abandonment is to prepare the equipment and personnel that will be involved in the operation, such as the vessels, cranes, cutting tools, lifting devices, grouting units, divers, ROVs, engineers, technicians, and supervisors. You will need to ensure that the equipment and personnel are fit for purpose, certified, trained, and insured, and that they follow the safety and quality procedures. You will also need to plan the logistics, such as the transportation, storage, disposal, or recycling of the pipeline materials and equipment.

4 Execute the decommissioning and abandonment

The fourth step in planning subsea pipeline decommissioning and abandonment is to execute the decommissioning and abandonment method that you have chosen, according to the design, schedule, budget, and contract. You will need to perform the necessary tasks, such as isolating, flushing, cleaning, cutting, lifting, grouting, or burying the pipeline segments, and verify that they are done correctly and efficiently. You will also need to monitor and control the operation, such as the weather, sea state, currents, visibility, depth, tension, load, and alignment, and deal with any contingencies or deviations that may occur.

5 Restore the site and environment

The fifth step in planning subsea pipeline decommissioning and abandonment is to restore the site and environment to their original or acceptable condition, as agreed with the stakeholders and regulators. You will need to remove any debris, waste, or hazards that may have been generated during the decommissioning and abandonment operation, and ensure that they are properly disposed of or recycled. You will also need to conduct a post-decommissioning survey and assessment to confirm that the site and environment are safe and stable, and that there are no adverse effects or liabilities.

6 Evaluate the performance and lessons learned

The sixth and final step in planning subsea pipeline decommissioning and abandonment is to evaluate the performance and lessons learned from the operation, and to document and share them with the stakeholders and regulators. You will need to measure and compare the actual results with the expected objectives, such as the cost, time, quality, safety, and environmental impact of the decommissioning and abandonment method. You will also need to identify and analyze the strengths, weaknesses, opportunities, and threats of the operation, and to recommend any improvements or best practices for future projects.