03 Key Points to Note in the Work of Abandoning Oil and Gas Wells

03 key points to note in the oil and gas well abandonment process (Illustrative image)

Circular 17/2020/TT-BCT regulates well abandonment as the retrieval of downhole equipment, reinforcement of cement plugs, installation of mechanical plugs, cutting and retrieving some sections of casing in the well, and clearing obstacles (if any) around the wellhead and wellbore. It specifies 03 key points to note in the oil and gas well abandonment process as follows:

1. Cutting and Retrieving Casing, Wellhead, Downhole Equipment

According to Clause 4, Article 16 of Circular 17/2020/TT-BCT, when cutting the casing, the operator must consider the following points:

- If the overlapping section of two casing strings is not cemented, then the inner casing can be cut and retrieved. The cutting depth is based on the height of the cement column in the annulus, determined through well log data.- If there is a possibility of residual pressure existing in the annulus outside the casing, it must be thoroughly addressed before proceeding with casing cutting using supplementary technical measures as regulated.- Before cutting the casing, the weight of the drilling fluid in the well must be adjusted according to the formation strength at the casing shoe.

In addition, operators must note:

- The operator must use mechanical or hydraulic methods to cut and retrieve the wellhead.- For onshore wells, the cutting depth for the wellhead and casing must be at least 3 meters below the ground surface.- The operator must not retrieve casing set in the well unless approved in writing by the Vietnam Oil and Gas Group.

2. Fluid Used in Well Abandonment

- When a part or the entire well is abandoned, it must be filled with fluid of sufficient density to control the existing pressure in the formation before conducting well abandonment operations.- The fluid in the well must be treated to prevent corrosion of the casing.- For the open hole section before setting the cement plug, a high-viscosity buffer fluid must be placed to prevent cement from settling at the bottom of the well.

3. Cement Used for Well Abandonment

- The cement used to set any cement plug in the well must have a minimum compressive strength of 3,000 kPa (435 psi) after setting for 8 hours.- For high-temperature and high-pressure wells, the cement used to set any cement plug in the well must have a minimum compressive strength of 3,500 kPa (508 psi) after setting for 48 hours.

For more details, see Circular 17/2020/TT-BCT effective from September 10, 2020.

Ty Na

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