DECOMMISSIONING: ALL YOU NEED TO KNOW

• Decommissioning encompasses securely sealing the opening in the Earth's surface and managing the removal of equipment utilized in offshore oil production. 
• This sector is swiftly evolving in the petroleum industry, presenting significant opportunities and risks.
• It poses substantial liabilities for counties, operators, contractors, and the public, requiring a thorough understanding for effective cost management.

source: jpt

Decommissioning of a well is simply all the processes involved in ending oil and gas operations and making the site environmentally friendly and useful after drilling.

Decommissioning can be done both on shore and offshore.

PROCESS OF DECOMMISSIONING 

Offshore decommissioning involves a comprehensive 10-step process, starting with project management, engineering, and planning, followed by permitting, platform preparation, well plugging and abandonment, conductor removal, mobilization and demobilization of derrick barges, platform removal, pipeline and power cable decommissioning, materials disposal, and site clearance.

Key aspects include extensive project planning, obtaining permits, preparing platforms by cleaning equipment, well plugging with a focus on safety measures, conductor casing removal through various methods, mobilization and demobilization of equipment for platform removal, and decommissioning of pipelines and power cables based on regulatory considerations. 

The process requires meticulous coordination and adherence to environmental and safety standards.

Below is a video of decommissioning of the Bravo Oil Platform (source: TikTok)

COST OF DECOMMISSIONING 

The expense associated with dismantling a platform can be influenced by various factors that continually change. Key considerations include factors like location, water depth, and the platform's purpose, such as being used for oil or gas extraction.

The primary determinant in the decommissioning process is directly tied to the weight of the materials requiring removal. Emphasizing operations focused on disconnecting and removing components can result in cost savings. Removal costs constitute almost two-thirds of the overall decommissioning expenses, underscoring the importance of selecting a contractor with excellent equipment, experience, and service.

Reducing decommissioning costs is achievable through thoughtful initial design that incorporates a methodology for decommissioning and adapts the design accordingly.

ALTERNATIVES TO DECOMMISSIONING 

Many operators opt to reuse parts of offshore platforms due to decommissioning costs. The decision depends on factors like wear and tear, intended use, and corrosion. 

Gorman and Neilson's study in "Decommissioning Offshore Structures" explores considerations for reuse. Recent alternatives include wind and water power generation, with wind turbines on platforms and platform modification for wave-based electricity. 

The "Rigs to Reefs" policy in the Gulf of Mexico transforms decommissioned platforms into permanent reefs. Fish cages introduced into platform jackets offer an oceanography solution, allowing coastal fish farming. 

Each alternative must be assessed case by case considering eligibility, local policies, and environmental safety.

DISPOSING MATERIALS 

Platform materials can undergo refurbishment for reuse, recycling, or disposal in designated landfills. Operators must adhere to a four-step site clearance process to ensure proper decommissioning. 

A pre-decommissioning survey maps debris, pipelines, power cables, and marine environments. 

Post decommissioning, surveys identify remaining debris and note environmental damage. 

ROVs and divers are deployed to identify and remove any interference, and test trawling confirms the area is obstruction-free.

source: petrowiki.spe.org 

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