Set Downhole Tubing Plug (SOP)

Downhole Tubing Plug (DTP) Set

Introduction

A downhole tubing plug is a type of barrier set in well intervention and workover operations. Tubing plugs are primarily used to isolate the wellbore to facilitate controlled intervention without fluids from other sections of the wellbore migrating. Well design depends on proper installation, which guarantees operational safety, efficiency, and integrity of the well. This is a detailed article on the Down Hole Tubing Plug SOP with regards to general principles, tools and SOP.

General Requirements

The following are general requirements that need to be satisfied to provide for successful tubing plug installation:

✔Inspection of Plug: Visually check the plug for scratches, dents, and visible damage — before inserting. If things go wrong during setup, scratches or dents can again provide diagnostic insight.

✔Use of Correct Running Tool: Use the appropriate running tool for the lock mandrel type used. To run ‘R’-type lock mandrels the ‘R’-type running tool must be used. A ‘GS’ pulling tool would NEVER be used when running ‘R’ locks, which could otherwise result in improper installation.

✔Check Key Spring Tension: Check the spring tension after installing the lock mandrel on the running tool. Make sure the springs keep the keys fully extended (but allow pull back under force).

✔Run in Selective Position: The plug shall always be running with a selective position. Thread it through the nipple, and pull back up to seat it.

Note: This process keeps the keys clear of things like mill scale, rust, or chemical buildup on the tubing wall.

Watch out for potential recesses in the tubing-to-nipple connection which could accept the locking keys, especially where the tubing may have a different thread weight than that of the nipple.

---If pup joints or flow couplings are located above the nipple with the same thread weight, do not travel above them into different thread-weight tubing.

✔Install Latch Shear Pin Spring: All plugs shall be equipped with latch shear pin springs. The latch shear pin must always be used unless otherwise authorized by the Service Coordinator.

✔Using Steel Pins in the ‘R’ Running Tool: ‘R’ running tool is with DI, two steel pins to be used. This helps avoid the lower pin shearing in the nipple prematurely on installation.

Selection of Plug Type

✔The PR plug functions best in deep-set applications owing to its high tolerance for debris.

✔The RO plug is most commonly for use in shallow-set applications.

✔The PR plug has two trips, one to set the plug and the other to set the equalizing prong.

When gas purging, plug all but one EQ port hole when installing the PR for a controlled prong ejection (Fast ejection can occur if no ports are plugged). All the ports must stay open in an agile environment. Ports are sealed with a hex nut screw that is supplied by the wireline operator. Port Status (Plugged/Open) should be saved as part of Daily Work Report, which can be retrieved later.

How to Set a Downhole Tubing Plug:

✔Rig Up (R/U) the Wireline Equipment

✔Install 10M-psig wireline BOPs and lubricator

✔Prepare plug and plug setting tool.

✔Open the Necessary Valves

✔Control Valve (CV), Tree Kill Valve (TKV) and 'Lo-torque' on TKV Open

Lubricator Pressure Test: Perform a pressure test to 7500 psig. Use a 70% - 30% mix of water and glycol.

Bleed Down Tree Pressure:

✔Shut-In Wellhead Pressure (SIWHP) reduction

✔Close the Tree Kill Valve

✔Bleed test line pressure.

✔B/D ‘Lo-torque’ valve Closed.

✔Open Master & Hydraulic Master Valves

✔Fluid communication for tool deployment

✔Run In Hole (RIH} with Plug and Setting Tool

✔Run the tool string and set the plug at the required depth according to the work program.

✔Check the Tool Position in the Lubricator

✔Return the CV to home and count how many turns to verify that the tool is retracted.

✔Bleed the Tree to 1,000 psig

✔Read well pressure for 10 minutes.

✔Hydraulic Master Valve (HMV) Close

✔Isolate the wellbore from surface pressure

✔Bleed Lubricator Pressure

✔CV open to allow for complete pressure bleed off

✔Flush Wellhead (If Allowable)

✔Then wash the system with methanol to eliminate any sour gas residue.

✔Close B/D ‘Lo-torque’ Valve

instance after itself.

✔For the W/L Maintenance: Rig Down (R/D) the Wireline Lubricator

✔Do not prematurely remove wireline pressure control equipment.

✔Secure the Wellhead Tree

✔Check that all valves are closed and locked.

Conclusion

It requires special tools, strict process and skill to set a downhole tubing plug. Adhering to the Standard Operating Procedures (SOP) in the guide below enhances operational robustness, mitigates potential hazards, and upholds the integrity of the well. A meticulous examination of the plug, combined with the right running tools and methodical procedural approach, results in successful deployment and retrieval of the plug without too many issues.

Refer here FOPENGG to know in detail about well intervention with workover operations and best practices of petroleum industry.