The Weight Bar That Nearly Failed a Gunstring and Why We Rebuilt Our Redress Routine

Posted on by Crissa Fel Tawadan

In the wireline world, failures don’t always explode—they erode. One misfit sub here, a mismatched thread there. And suddenly, your gunstring is in the hole, your logging cable is hot, and your continuity check just failed with no clear explanation.

That’s exactly what happened to us on a recent cased hole wireline job. It was a routine pump down perforating operation in a horizontal well—nothing fancy, nothing high-risk. But our weight bar setup, rebuilt earlier in the yard, didn’t meet spec. And that small oversight nearly triggered a misrun on a full-stage wireline perforating job.

This story became the reason we overhauled our weight bar redress process across every yard, rig-up, and field location. It’s now standard practice across our teams and built into the foundation of our wireline courses and internal wireline services QA checklists.

The Setup Looked Normal

We were in the prep yard, assembling a standard toolstring: weight bar, casing collar locator, switch sub, perforating gun, and pressure control stack. This was a typical setup for any wireline provider working in the wireline services oil and gas sector.

Everything looked clean—threads greased, contact pins checked, connectors torqued. But the weight bar wasn’t rebuilt by our crew. It had been redressed earlier that week by another shift. No flags were raised during handover.

That assumption cost us hours.

A Mismatched Sub That Slipped Through

On the first continuity check, we saw a drop. Not a complete open—not yet. But the reading wasn’t stable. We disconnected the wireline truck, tested the head, cleaned connectors, and reseated every joint. Still unstable. Finally, we broke down the toolstring and inspected the weight bar.

That’s when we found the issue: the subs were redressed using the wrong kit. The Acme pin sub was installed on one end, but it had the wrong pin dimensions internally. The contact pin on the weight bar side was shorter than spec, and the external pin didn’t seat fully into the CCL. No wonder we had inconsistent signal.

Had we gone in hole, it would’ve been worse—a possible failure mid-run, or worse, a fishing wire line situation with misfired guns stuck below a misconnected head.

Understanding the Weight Bar Sub Redress Differences

Most people in wireline have dealt with redressing weight bars. But few take time to understand the difference between the sub kits. That’s what this job made painfully clear.

There are multiple configurations of weight bar sub kits used in wireline equipment:

  • Acme Pin Sub (Top): Long external pin, short internal pin

  • Acme Box Sub (Bottom): Short internal threads for rod contact

  • GO Pin Sub: Identical pins on both ends

  • Tandem Sub: Same as GO, matched pins both sides

If you mix these up, you risk damaging both the weight bar and the electrical path to your perforating system.

That’s why this job led to a new SOP that every crew in our operation now follows religiously.

Our Updated Redress and Verification Procedure

Here’s the process we now follow, whether prepping for a single-stage perforation well or a full production logging setup:

1. Maintain and Use the Correct Redress Kits

  • Kits for Acme, GO, and Tandem subs are stored separately, labeled, and tracked.

  • A list of part numbers is mounted inside every tool trailer and gun room.

2. Always Rebuild Equipment If You Didn’t Redress It Yourself

  • No assumptions. If your crew didn’t rebuild the weight bar or CCL, you must tear it down and verify internals.

  • This includes rod lengths, thread condition, and pin contact spacing.

3. Physical and Electrical Inspection Before Assembly

  • Confirm that pin contact lengths match spec using a caliper.

  • Test each rod for continuity before assembly.

  • Inspect insulators, sleeves, and seals to confirm they’re correct for the sub type.

4. Torque and Thread Verification

  • Ensure proper torque specs for the redressed parts.

  • Look for over-tightening, cross-threading, or mismatched thread pitches.

  • Check that redressed rods don’t “bottom out” too early—especially critical for wireline control systems.

5. Document and Double-Check

  • Every weight bar rebuild is logged with the tech’s name, date, and kit used.

  • This document follows the job into the field and is verified by the engineer before rig-up.

Why This Matters for Wireline Providers

In the cased hole logging service market, performance isn’t just about tools—it’s about systems. When you’re delivering wireline and perforating services on tight frac schedules, a 30-minute misrun can set back an entire crew rotation, cost thousands in downtime, and damage trust with the client.

Proper weight bar assembly supports:

  • Reliable perforating gun firing

  • Accurate depth correlation with cased hole logging tools

  • Consistent signal continuity for CBL logs, production logging services, and formation evaluation

And, most importantly—it supports well integrity.

Bringing This Lesson Into Training

We now include this redress lesson in our wireline courses—from new-hire training to advanced troubleshooting. Trainees handle mismatched subs, inspect damaged pins, and learn how the wrong configuration compromises both safety and functionality.

They also get exposure to:

  • Redress kit selection by application (e.g., plug and abandon, perforation services, pipe caliper tool deployments)

  • How to identify wear on electrical pins

  • How to validate rod length and contact pressure

  • The risks of running mismatched parts under pressure

Building a Culture of Ownership

It’s not enough to know how to rebuild a weight bar—you have to understand why it matters. In today’s wireline oilfield, every component impacts safety, performance, and crew accountability.

We’ve made this part of our field leadership conversations. Crews are encouraged to “own the redress” and report any inconsistencies immediately. We treat redress just like we treat detonator handling or logging cable care—non-negotiable.

Conclusion – Precision Starts in the Yard

It’s easy to overlook small mistakes in a rush. But in wireline logging, those small mistakes are what bite the hardest. If you’re managing a wireline company, overseeing wireline trucks, or trying to grow your reputation in the wireline services market, start with the fundamentals.

Redress with precision. Inspect with intent. And never run a tool you didn’t verify yourself.