In wireline, every run is a high-stakes operation. Between the pressure control systems, the electrical diagnostics, and the explosives packed into every perforating gun, the only thing standing between a flawless job and a flooded gunstring is attention to detail.

A while back, during a pump down perforating run on a horizontal well, we learned that lesson the hard way. The job looked like any other: high-shot count, multiple stages, pressure-tested iron, verified logging cable, and a clean run sheet. What we didn’t have was a complete inspection on the back end after troubleshooting a switch.

That single oversight—one missing port plug—flooded the gunstring, stopped the job, and turned a routine operation into a full lesson in wireline accountability.

The Job Started Smooth

The string was built by the book. The wireline truck crew prepped everything—wireline tools, pressure control equipment, and the gunstring itself. I was on the job as the engineer, reviewing every piece before we ran in hole. Gaps between subs? Checked. All port plugs? Present. Brass seated in the setting tools? Verified. The red power charge caps, shear screws, nylon plugs—all accounted for.

Before going live, we ran a switch test. One of the switches read open (19 µA), so I instructed the crew to remove the port plug near the failed switch and the one above it. They replaced the faulty switch, we retested, and both port plugs were reinstalled. I verified them myself.

Everything was back in tolerance. We equalized and began running in.

Then We Hit 200 Feet

About 200 feet into the run, we performed another switch test. One switch failed—this time showing a short. Being so close to surface, I made the call to pull out and investigate.

And that’s when we found it.

During the earlier troubleshooting, in the flurry of action, someone had pulled a third port plug. Not the one we replaced. Not the one above it. A completely separate plug. I wasn’t told, and it wasn’t inspected. That one plug—forgotten and unverified—let fluid into the gun, flooded the string, and rendered the entire assembly useless.

A $10 Plug That Nearly Shut Down a $100,000 Job

Let me be clear: this wasn’t a hardware failure. It wasn’t a bad connection, broken wire, or misfire due to faulty manufacturing.

It was a process failure.

In wireline well logging and wireline and perforating work, every small part matters. The gunstring is the heart of the operation, and one missing port plug can stop the entire thing. It might just be the cheapest part of the assembly—but it carries some of the highest risk if ignored.

This wasn’t the first time the industry has seen a flooded string, but it was the last time it would happen under my watch. From that day forward, we created a rigorous post-troubleshooting verification system that’s now part of our company SOP and included in all our wireline courses.

The New Gunstring Verification Procedure

Now, before any gunstring is run in a cased hole wireline job, especially after a failure or operational change, the following checks are mandatory. Every step is verified first by the lead operator and then double-checked by the engineer:

1. All Port Plugs Are Present and Seated

• Physically touch and confirm every port plug.

• Inspect threads for wear and ensure full seating into the sub.

2. Brass Shear Screws Are Properly Seated

• Check that every brass shear screw is in place, tight, and not stripped.

• Verify nylon plugs and red power charge caps are installed correctly.

3. Make-Up Connections Are Fully Tightened

• Every sub is torqued correctly.

• Visual confirmation that threads are engaged and not gapped.

4. Wireline Head and Logging Cable Are Serviceable

• Full inspection of cablehead and connection pins.

• Confirm clean insulation, no crushed connectors, and functional signal.

5. Correct Gun Count, Shot Count, and Phasing

• Cross-reference the gun count and shot phasing with the well plan.

• Confirm proper alignment with perforation services staging.

Why These Checks Matter in the Wireline Services Market

In today’s wireline services oil and gas environment, mistakes don’t just delay a stage—they ripple through the entire operation. Delays cost time, money, and client trust.

That’s why this protocol now exists across every wireline provider in our region. It supports performance and consistency, especially during:

• Cased hole logging

• Horizontal wireline runs

• Wireline perforating operations with complex gun configurations

• Plug and abandon and pipe recovery services

• Downhole camera or holefinder tool deployments

• Formation evaluation runs requiring exact trigger timing

A Culture of Accountability

This incident also led us to reevaluate our culture. Previously, after a failed switch test, the assumption was that once the fix was complete and the engineer verified the immediate area, the string was good to go. Not anymore.

Now, any troubleshooting—any deviation from the original assembly—triggers a full gunstring recheck. The lead operator is responsible for documenting changes. The engineer signs off on them. And both verify every component from top to bottom before the string leaves the floor.

This has now become the standard in our wireline company and is embedded in every training path we offer.

Lessons for the Next Generation

In every wireline course I teach now, this incident is part of the curriculum. Because what is wireline in oil and gas if not a sequence of high-risk, high-precision tasks where one missed check can derail an entire operation?

We walk trainees through real failure photos—flooded guns, corroded wires, port plug damage—and they learn:

• How to spot missing or mismatched hardware

• How to verify port plugs using thread depth and tool engagement

• How to visually identify incorrect gun phasing

• Why switch tests alone aren’t enough if you skip physical inspection

They’re taught to take responsibility for their string—not just because they’re told to, but because they understand what happens if they don’t.

Final Thoughts – Small Details, Big Consequences

Wireline is unforgiving. You can do 99 things right, but if you forget to check that last port plug, it won’t matter. That’s the reality of this job—and the reason we double check everything, every time.

If you’re in charge of a crew, running a wireline truck, or managing a wireline business in today’s competitive wireline services market, start by making sure your team understands the value of one final check.