Temporary well abandonment and well control : best practices for H₂S-containing wells
Temporary well abandonment, TWA, is a vital technique in oil and gas operations that is used to guarantee well integrity and safety when workover or drilling operations are suspended briefly. For H₂S-containing wells, adequate precautions must be executed to prevent corrosion, assure pressure control, and allow re-entry. This document calls for the best practices for temporary well abandonment* and well control* that consists of proper sealing, well control equipment, using corrosion-resistant materials, and meeting industry standards to maintain well integrity during the suspension period.
Temporary well abandonment:
Temporary well abandonment is employed when TWA operations are halted due to unplanned occurrences such as equipment failure, hurricane conditions, terrorist threats, and evacuation requirements. TWA is different from permanent abandonment since TWA operations are intended to be restored as soon as feasible. As a result, it is critical to conduct well control** measures throughout the suspension period and employ equipment that helps to isolate the zone and excludes uncontrolled movement of the fluid.
Temporary well abandonment objectives:
Maintain well integrity.
Assure of pressure control.
Protect from corrosion and use anti-corrosive materials.
Able to gain access in the future.
H₂S Resistant – Constructed of Inconel, stainless steel, or sour gas resistant elastomers.
Pressure Rated – Withstands reservoir pressure and differential pressures
Corrosion Proofed – Welded, coated or treated to be resistant to sulfide stress cracking (SSC) and hydrogen-induced cracking (HIC)
Cementing on Top of Bridge Plug Packer
For further well isolation, a cement plug should be spotted above the bridge plug packer. This provides an extra barrier serving many purposes:
Offers Extra Sealing – Minimizes the likelihood of fluid movement
Stops Microbial and Chemical Corrosion – Slows decay through time.
Migrates Into Long-Term Stability – Nesting Abandonment techniques will stay effective till its re-entry.
Abandonment Procedures for Temporary Wells
The following procedural steps describe how to temporarily abandon a well under industry regulation and safety guidelines.
Step 1: Preparing the Wells and Managing the Fluids
— Vibrate the well to death with appropriate weight kill fluid (i.e. brine or mud containing corrosion inhibitors).
Perform well circulation for the removal of hydrocarbons and reduction of gas pockets.
Barriers should be set in a clean wellbore free of debris.
Step 2: Generate an Intermediate Production String with Packer
A temporary production string, ideally with a packer, should be run in the hole.
The packer aids in isolating the reservoir while enabling controlled rein filling.
Use of a retrievable packer allows for easier access and restoring of the wellbore when operations resume
(Set Bridge Plug and Cement) Press to complete this step.
Set the H₂S-resistant bridge plug packer at the desired depth.
You can use these to spot cement on top of the bridge plug for more isolation.
Perform pressure tests to verify the integrity of the seal.
Step Four: Measuring and Securing Wellhead and Surface Equipment
Wellhead protectors and pressure gauges to be installed.
Lock the X-mas tree or wellhead assembly properly with suitable lock mechanisms.
Sign the well with TWA signage (Status, depth, and plans for re-entry)
Industry standards and best practices
International and regional well control regulations govern procedures for temporary well abandonment. To name a few of the relevant industry standards:
API — American Petroleum Institute Recommended Practice for Temporary Abandonment of Wells.
NORSOK – Norwegian well integrity standard.
OGP Report -- International Association of Oil & Gas Producers well control recommendations.
Saudi Aramco Well Control Standards – Prescriptive for Hydrogen Sulphide H₂S and sour gas wells
A Temporary Well Abandonment Procedure
Challenge 1 Corrosion from H₂S exposure
– Solution: Use corrosion-resistant packers, tubing and casing materials Use chemical inhibitors and watch fluid chemistry.
Challenge 2: Evacuation while Maintaining Well Control
Answer: Use a *well control contingency plan complemented with pre-placed kill-weight fluid and a well monitoring system
Challenge 3: Unclear Re-Opening Timeline
Solution: Maintain *status, pressure, and integrity documentation of all wells to facilitate their easy reactivation.
Conclusion
Temporary well abandonment is a temporary well control procedure that is essential for safety, well integrity, and regulatory compliance. The expected H₂S service guidelines must also be followed when developing H₂S-containing wells, particularly with regards to the selection of corrosion-resistant bridge plug packers, cement barriers, and overall well closure for potential re-entry. Operators can also identify key decisions they need to make in the latest stage of well suspension and in managing the job within the context of using best practices and working to standards, minimizing risks of operations.
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