What is Abandonment and Decommissioning (A&D)

  • Abandonment : The process of permanently shutting down a well by plugging it, removing equipment, and ensuring it poses no safety or environmental risks.
  • ​Decommissioning : Broader than abandonment – it includes removing offshore platforms, pipelines, subsea equipment, and restoring the site to its natural condition.

Importance and Objectives

Decommissioning and abandonment aim to thoroughly contain remaining hydrocarbons, protect groundwater reserves, and minimize environmental impact by clearing up and filling wells, and removing its infrastructure.  It also limits fluid movement until nature restores the pressure balance that existed prior to the drilling. Abandoned oil and gas fields are made safer for the sites to be restored to their original state, and made available for productive use again.However this needs to be managed more cost effectively to avoid being a liability for operators, contractors and the public. Also, decommissioned sites retain hazardous inventory for decades if not done properly, and may even require new equipment depending on the level of contamination.
While the oil and gas industry advances globally, the financial burden of decommissioning platforms grows. Proper management is crucial to mitigate environmental hazards and repurpose sites productively.

Key Components

  • Plugging & Abandonment (P&A) 
​          Cement plugs are placed inside the well to seal hydrocarbon zones and prevent fluid migration.
          Equipment such as tubing and casing is removed, and the wellhead is cut below ground level (onshore) or seabed (offshore).
  • Removal of Structures
​          Offshore platforms, subsea pipelines, and onshore surface facilities are dismantled and removed.
          This may involve heavy-lift vessels for offshore topsides, subsea cutting of jacket legs, and pipeline decommission
  • Reclamation / Remediation
    The land or seabed is restored to a safe and natural condition after decommissioning.
    This may include removing debris, remediating contaminated soils, and seabed clearance.
    Sometimes offshore rigs are converted to artificial reefs (Rigs-to-Reefs program).

Regulatory requirement

  • Strict regulations enforced by governments
          Agencies such as BSEE (US), NOPSEMA (Australia), and DMF (Thailand) oversee decommissioning. They review and approve plans, enforce             safety and environmental standards, and monitor compliance to ensure projects follow national and international rules.
  • Operators’ legal responsibility
    Operators must cover all costs and ensure safe decommissioning, including well plugging, structure removal, and site restoration. In many regions, liability remains even after ownership changes, preventing companies from avoiding obligations.
  • Environmental Impact Assessments (EIAs)
    EIAs are often required to evaluate effects on ecosystems, fisheries, and coastal areas. Regulators may require mitigation measures such as careful waste disposal, low-impact removal techniques, or partial removal if it benefits the environment (e.g., artificial reefs).

Economic Considerations

  • High cost
    Decommissioning is among the most expensive stages in an oil and gas project. Onshore facilities may cost tens of millions, while large offshore projects can reach billions. Costs depend on water depth, platform complexity, number of wells, subsea equipment, and environmental restoration. Actual expenses are often uncertain until work begins because equipment conditions may not be fully known.
  • Cost estimation and funding
    Companies prepare Abandonment Cost Estimation (ACE) early to forecast future expenses. Many build a decommissioning reserve fund during production to spread the cost over time. Regulators may also require financial assurance, such as bonds or trust funds, to ensure obligations are met and to avoid abandoned infrastructure becoming a government burden.
  • Timing
    Early abandonment lowers future risks and operating costs but reduces revenue from unrecovered resources. Delayed abandonment allows greater recovery and extended revenue, yet often raises costs due to inflation, equipment deterioration, and stricter regulations. Operators must balance profit potential with long-term risks.
  • Wider economic impact
    Decommissioning supports contractors, vessels, engineering services, and waste management, creating jobs and benefiting local economies. However, cost overruns are common, and if operators lack funds, governments may face the costly task of removing orphaned infrastructure.

​Environmental & Safety Concerns

  • Risk of well leaks, gas migration, or subsidence if not sealed properly.
  • Offshore structures can impact marine ecosystems.
  • ​Need for safe disposal of hazardous materials (e.g., chemicals, hydrocarbons, asbestos).

Alternative Approaches

  • Rig-to-reef programs: Offshore platforms converted into artificial reefs.
  • ​​Re-use of infrastructure for CO₂ storage (CCS), geothermal, or hydrogen projects.

Thailand’s Oil & Gas Decommissioning
​and Abandonment Framework

  • Thailand faces a major decommissioning challenge, with over 400 offshore platforms nearing the end of their life.
  • The process is governed by the Department of Mineral Fuels (DMF) under a clear regulatory framework, requiring operators to submit decommissioning plans and maintain financial security.
  • ​Key activities include well plugging & abandonment, platform removal, pipeline handling, site clearance, and waste management, with strict environmental considerations.
  • Challenges remain around high costs, liability disputes, and technical complexity, but opportunities exist for international contractors, local industry growth, and environmental initiatives such as rigs-to-reefs.
  • Effective decommissioning is essential for ensuring safety, environmental protection, and sustainable energy transition in Thailand