Workover operations: from well failure to production restart

Lesson Summary

When do we need a Workover, and what are its basic stages: killing the well, pulling the completion, repair, and production restart.

This lesson is part of the Well Intervention track, with a duration of 4:57 minutes. Watch the video first, then review the key points and test your understanding with the questions below.

Key Points

1. 1Used when completion fails or production declines.
2. 2Usually starts by killing the well and installing the BOP.
3. 3Ends with restarting and testing the well.

Written Lesson

What is a Workover?

A Workover is a major maintenance operation on a producing or injecting well, aimed at restoring or enhancing production, or repairing a completion or integrity failure. It differs from drilling because the well already exists, and from light Wireline intervention because it often requires pulling the completion and using a workover rig.

When is it Needed?

• Leak in the Tubing, Packer, or any completion component.
• Production decline due to near-wellbore damage, sand, or scale.
• High water or gas cut due to isolation failure.
• Changing the artificial lift system or modifying the completion.
• Moving to another zone (Recompletion), or plugging a depleted zone.
• Well integrity issues, such as unexplained annular pressure.

The decision is preceded by a diagnosis: analyzing production data, pressure tests, and production logs to identify the root cause before committing to high costs.

Step-by-Step Stages

• Failure diagnosis and establishing a written, approved program for the operation.
• Securing the well: Killing it with suitable fluid or setting barriers, and ensuring no hazardous pressure exists.
• Removing the Christmas Tree, installing the BOP stack, and testing it.
• Pulling the Completion and inspecting every component.
• Repair or intervention: Cleanout, part replacement, reperforating, or formation treatment.
• Running Back the completion and setting the Packer.
• Removing the BOP, reinstalling the tree, and pressure testing.
• Restarting and monitoring the well, then handing it over to the production team.

Barriers and Kill Fluid Calculation

Fundamental safety rule before pulling completion: having at least two independent barriers between the formation and surface, one usually being the kill fluid column. Fluid weight is calculated to provide hydrostatic pressure higher than formation pressure by a safety margin.

Calculated example: Reservoir pressure 4,160 psi at 8,000 ft TVD. Balance weight = 4,160 ÷ (0.052 × 8,000) = 10.0 ppg. Adding a 200 psi safety margin, the required density is (4,160 + 200) ÷ 416 ≈ 10.5 ppg. However, heavier fluid may leak and damage the formation; the decision balances safety and reservoir protection, which is why clean completion fluids like brines are often used.

Alternatives to Heavy Operations

Lighter alternatives may replace a workover rig: Slickline and Wireline for light tasks, Coiled Tubing for cleanouts and treatments, and Snubbing when killing the well is undesirable. The best option is chosen based on the problem, well condition, and cost.

Questions to test your understanding

Before pulling the completion during a Workover operation, what is the most important consideration? Answer: Well barriers and pressure control requirements, not just string weight or operation duration. Figures provided are for educational purposes; your specific well program is the primary reference.

Lesson Glossary