Decommissioning of Oil and Gas Installations

In a world of depleting fossil fuels, oil and natural gas are one of the most consumed and exploited natural resources. Averaging a consumption of 93 barrels per day and 120 Trillion cubic feet for Oil and natural gas respectively, they can be considered as the most important fuels that the mankind is using right now. The entire human race is focused on using these precious resources and is least bothered about where these resources actually come from or whether their supply meets the demand. With just 55 years or so for these resources to run out we are not even concerned or ready to curb or even put a leash on the staggering consumption rates. With oil wells being the major producer of both oil and natural gas in the world, these are an indispensable factor in the oil and gas industry. So just as how important is the installation and commissioning of these wells, its safe decommissioning is also crucial.

Oil and Gas Installations

The offshore oil and gas industry had its humble beginning in the Gulf of Mexico in the year 1947.It was built 43 miles south-west of Morgan City which gradually sloped to the Gulf of Mexico with a depth of just 18 feet. Vessels were required to aid the platform with supplies, equipment and crew. Though this was a small and humble beginning, it paved the way for an enormous number of platforms to be installed to cater to the ever-increasing need of fuel in the world. Slowly but steadily the number of such rigs and installations increased and reached staggering 389 platforms with the North Sea having the most of it -184. The platforms we see today have changed from what we had. New efficient platforms and equipment were developed and are further being developed for efficient extraction of oil and gas from these rigs.

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 Decommissioning of oil and gas installations

Decommissioning of a constructed rig is as important as its installation. The North sea has seen the most number of decommissioned installations in the past 40-50 years, with almost 1500 decommissioned wells.

The majority of structures in the area have a water depth of around 3 to 300 meters and often encounter huge waves of height exceeding 10 meters. In these conditions the removal or decommissioning process could be highly difficult to execute. A major concern in this process is to carefully select the method to remove the structure from the sea bed and the support availability to aid this process in remote locations.

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So what is the basic process involved?

There are a lot of steps involved when it comes to decommissioning of oil and gas installations :

  1.Project Analysis:

In this step the entire project is evaluated from both a financial and an environmental point of view. Every aspect of the project going to be decommissioned is evaluated and verified to obtain the maximum financial and economic gain.

   2.Permitting and Regulatory agreement

Like any other process this also goes under the scrutiny of a wide legal framework. Obtaining permissions for decommissioning of an oil rig can take up to 3 years . In this time interval evaluations and tests are done on models and simulations. There are many authorities which are directly involved in the legal framework including BOEMRE, US Fish and Wildlife Society, National Oceanic and Atmospheric Administration, Department of Transportation, Office of Pipeline Safety etc.

  3.Platform Preparation

The tanks, piping and processing equipment must be cleaned and the residual hydrocarbons must be removed. Platform equipment like pipes must be removed and proper reinforcement of the structure should be completed.

  4.Wall plugging and Abandonment

This process takes up the major funds in the entire process. This involves plugging of the entire structure to avoid the entrance of water and abandonment of the structure.

  5.Conductor removal

According to many organizations all platform equipment including conductor casing must be removed to at least 15 ft below the ocean floor to attain approval.

 6.Mobilization/Demobilization and Platform Removal

This process is very vital. First the topside is removed and taken into a barge. Various processes are used for this removal. Topside can be removed all in one piece, in groups of modules, in reverse order of installation or in small pieces.  Removing of the jacket is often very costly and is the second step. It can be removed in a single lift or as small pieces based on the size of the installations.

 7.Pipeline and Power Cable Decommissioning

The pipelines and power cables are to be removed if they are considered a hazard during the permit process. The pipelines are first flushed with water and then disconnected from the structure followed by filling them with seawater and then finally the open end is plugged and buried 3 m below the seabed and covered with concrete.

 8.Materials disposal and Site clearance

The platform materials can be reused and refurbished, scrapped and recycled or disposed of in specified landfills.

Reasons for increased decommissioning of installations.

Decommissioning in the oil and gas industry has seen a rapid increase due to a lot of reasons. Many a times in the current scenario running a platform or installation is deemed a loss for the owners. A few of the reasons are listed below.

1) Decline in oil prices

     The price of oil has been in a constant decline for the past few years. With the dollar staying strong compared to other currencies and with the Middle – Eastern countries ready to pump out oil overseas, the price of oil is not expected to rise at a rapid pace anytime soon. The demand of oil has increased due to the availability of different types of fuels which are more economical and has resulted in a situation where the supply has exceeded the demand.

  2) Increased capacity of vessels.

The vessels now that are being built and the one’s already commissioned and running are of higher capacities as that compared to that of the earlier days. With the availability of super tankers now a days the amount of oil that can be carried by a vessel has increased by a huge margin.

 3) Regulations

     With more and more regulations that have come with the installation and operations of a rig the number of people that are involved in this industry are going down. The organizations that are involved are making it more difficult for the players in the market to own and operate a fully functional rig.

Like any other specialized field, sophisticated equipment are required for the decommissioning of a platform. Various specialized equipment and vessels are now available in the market catering to this sector.

Manufacturers like Damen are coming up with equipment which specialize in decommissioning. 

These vessels specialize in 3 aspects of oil and gas decommissioning.

1)     Topside decommissioning and maintenance
2)     Offshore platform removal
3)     Subsea cleaning and removal 

Modules that can be attached to normal ships are also being developed which can aid the decommissioning process. This method is deemed to be highly cost effective. The little tweaks that are involved can reduce the cost of the project by a huge margin. 

The add-ons can include:

1)     ROV spreads
2)     Subsea Cranes
3)     Jacket removal equipment


In the case of vessels that are specialized in the oil and decommissioning projects, the lifting capacity is of great importance. The major vessel available now is the 382-meter-long Pioneering Spirit with a lifting capacity of 48,000 tonnes. She completed her first heavy lift by removing 13,500 tonnes 100 km off the coast of Norway.

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  Article By- Sunand Krishna