Unconventional Technical Solution for Optimizing the Plug and Abandonment

AUTHORS: Dan Radacina – Eng., Dosco Petroservices Romania, Gheorghe Dima – Eng., Dosco Petroservices Romania, Horatiu Popescu – Dosco Petroservices Romania, Lazar Avram – Professor PhD Eng., Petroleum-Gas University of Ploiesti

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In this paper, the authors are presenting a hand on method applied in the field (well site) in such a way that an old hydrocarbon well out of production can be plugged at surface, allowing a correct hook up of a dedicated workover rig to be installed and connected with the subject well and carry on further a legal well plug and abandonment program, imposed by the national laws and regulations.

Furthermore, the method is allowing that the remaining fluids coming out of the well to be safely contained, loaded and transported at a suitable disposal site. In this way, the well can be properly plugged and abandoned and pollution in the area can be successfully reduced.

Due to its structure, methane (CH4) traps more heat in the atmosphere per molecule than carbon dioxide (CO2), making it 80 times more harmful than CO2 for 20 years after it is released.

Cutting methane emissions by 45 percent by 2030 could help us meet the Paris Agreement’s goal of limiting global warming to 1.5°C.

A major source of CH4 emissions are old hydrocarbon wells that have been abandoned by fossil fuel extraction industries. These wells may have been deactivated for long periods of time for economic reasons, due to lack of transfer of ownership or negligence, and therefore no longer have legal owners responsible for their technical maintenance.

As global rules and regulations on GHG emissions become increasingly stringent to meet the Green Deal targets, the regulated decommissioning process for these wells can be extremely costly.

Governments encourage and support this activity by providing economic incentives for commercial activities related to the proper abandonment of old wells.

 

Technical considerations

Old hydrocarbon wells (or orphan wells) have lost their mechanical and hydraulic integrity, which means that the fluid in the well, in the form of hydrocarbons and salt water, can reach the ground surface (Fig. 1). Much of these leaks can be attributed to broken plugs, inadequate plugging, loss of well integrity, including well surface equipment. This will lead to environmental contamination, GHG emissions, fire and explosion hazards, poison gas hazards.

In fact, landowners and/or business owners have had problems with these hazards from orphan wells located on their premises. It goes without saying that this type of well will have strong potential to contaminate the land, air and surface water around the wells, groundwater, and may harm ecosystems, wildlife, livestock and people.

In Romania, the activity of plugging and abandonment of old hydrocarbon wells is regulated by specific national entities, such as the National Agency for Mineral Resources, together with the National Environmental Agency, requiring very specific technical measures from the operators, in order to meet all the requirements for the protection of groundwater, soil, air, environment and communities, so that the well can end its life cycle in a safe and reliable way.

It is understood that the activity of plugging and abandonment of old hydrocarbon wells generates major challenges driven by at least one of the following factors:

• Very little, incomplete or even non-existent data on wells
• Difficulty of effectively locating the subject wellhead in the field
• Absence of wellheads on the surface
• The conductor casing is buried at a depth of 3-7 m and at unknown coordinates
• Contamination of underground soil with oil and salt water
• Surface oil, gas, saltwater spills, naturally occurring or induced by technological injection programs
• Rough terrain
• Small workspace
• Overhead electrical cable
• Unknown underground service loops such as pipes, cables etc.
• Public roads, public/private facilities in the vicinity
• High costs due to legal requirements related to environmental protection
• Risk of explosion/fire with toxic gases.

Case study

An Oil and Gas Operator wanted to Plug and Abandon an old oil well, with no Wellhead or Xmas tree at surface, but with the damaged conductor casing buried 5 m deep. In this situation, there is no possibility to connect the existing damaged conductor casing or surface casing with any kind of pipe system in order to bring in a conventional workover rig and perform the necessary plug and abandonment work.

To solve this challenge, Dosco Petroservices Romania proposed and came up with the following sequence of operations and technologies:

-Running an underground Geoscan/Georadar mapping and determining the position of the existing buried well casing and the level of the underground fluids spill

-Excavation of a 4 m × 4 m × 5 m cellar around the buried casing and visual identification and assessment of the condition of the buried casing (Fig. 1)

-Reading and monitoring gas release from the well

-Containing and controlling the drainage of fluids coming out of the well

-Levelling and strengthening the working platform to support the related technical equipment

-Preparing, bringing and placing on site the following equipment:

• A 14 m 30″ joint fitted with a heavy-duty, open-bore flange (capable of withstanding mechanical hammer shocks) at one end and a bleed off valve on the side (Fig. 2)
• Tubing head with bonnet and master valve (Fig. 3)
• Crane of minimum 60 tons
• Hydraulic hammer S-90
• Working land frame

– Power pack to actuate the hydraulic hammer

• All necessary welding work has been performed off-site since the gas was detected.

-Depending on the situation(s) and the diameter of the existing casing, it will be covered by hammering blows over a 30″ casing joint to a depth of 13 m, or depending on the well conditions and the geotechnical survey conducted prior to the start of operations. (Fig. 4, 5 and 6).

-Once the required depth has been reached, a tubing head with a bonnet and a master valve shall be installed on top of the flange as shown in Fig. 7.

-The intermediate drain line shall be plugged with a small gate valve which shall be opened so that fluids exiting the well are drained and collected through a 2.3/8″ pipeline to a liquid collection tank.

-The well can now be connected to a workover rig to be properly abandoned in accordance with regulations and is handed back to the operator (Fig. 8 and Fig 9).

 

Conclusions

This is a fast and reliable method of plugging old wells by making a partial connection between the well and a workover rig, in order to safely perform the necessary well plug and abandonment operations.

The heavy flange and the tubing head are recoverable and can be used from one well to another, provided that the same casing diameter is used to hammer the conductor.

This method requires no on-site welding. All connections are threaded, and any welding work is carried out before the equipment is placed on the well site.

Crude oil fluids and/or saltwater coming out of the well can be safely contained and evacuated from the site so that spill/pollution in the well area is reduced.

This method is very quick – one working day is needed at the well site for each job, provided all the preliminary work has been done beforehand.

Dosco Petroservices Romania has carried out five similar works to date and a sixth is in the pipeline.

 

References

[1] Wikipedia, accessed in 2023

[2] Dosco Petroservices Romania SRL, Internal report, 2023