Every wireline engineer knows that perforating operations require precision—one wrong connection can mean a misfire, a tool failure, or worse, a downhole safety risk.
One day, we almost learned this lesson the hard way due to a simple but critical mistake in EB switch wiring.
The Setup: Standard EB Switch Perforating Job
It was a cased hole wireline perforating operation using EB switches to fire a series of perforating guns.
The job plan was straightforward:
- Assemble the perforating string with Titan EB switches.
- Verify continuity using a surface blaster meter.
- Pump down, fire in sequence, and achieve clean perforations.
Everything appeared good to go.
The Warning Sign: Unexpected Switch Failure
As we were performing our final electrical continuity check, we noticed an intermittent reading on one of the EB switches.
At first, we thought:
- Loose ground connection?
- Damaged conductor?
- Faulty switch?
But the real problem was something much simpler—and much more dangerous.
The Root Cause: Twisted Wires in the EB Switch
Upon inspection, we found that the switch wires had been twisted together during installation.
This small mistake had a huge impact:
- The twisted wires shifted inside the sub when the switch was set.
- The insulation on the wires got scraped off as they pressed against the sub wall.
- This exposed the conductor, creating a short circuit that could have prevented detonation or caused an unintentional misfire.
This wasn’t just a minor issue—this kind of failure could have led to a downhole misrun, requiring a costly and time-consuming fishing operation.
Fixing the Issue: The Right Way to Install EB Switch Wires
To prevent this from happening again, we followed the correct procedure:
- Never twist, tape, heat shrink, or bind the wires together.
- Keep the wires straight and free-moving inside the switch housing.
- Ensure wires do not press against the sub wall, preventing insulation damage.
- Perform a final continuity check before running in-hole.
With these corrective actions, we reassembled the toolstring, ran the final checks, and proceeded with the perforation job without issues.
Key Takeaways for Wireline Engineers
This experience reinforced several critical lessons:
- Twisting EB switch wires can cause insulation failure.
- Always leave them free-moving to avoid electrical shorts.
- Misfires and misruns often come from small mistakes.
- A minor installation error could have compromised the entire perforation sequence.
- Always verify electrical integrity before running in-hole.
- A simple continuity test saved us from a potential tool failure.
- Downhole tool safety is non-negotiable.
- This preventable issue could have led to serious operational delays.
Final Thoughts: Attention to Detail Prevents Costly Mistakes
In wireline perforating, every detail matters—even something as simple as how switch wires are arranged.
That day, a routine check saved us from a misfire. But it was a reminder that in wireline services, safety, and efficiency go hand in hand.