Some wireline jobs teach you about the well. Others teach you about yourself. But this one? It showed me the value of understanding your tools inside and out, especially when that knowledge can be the difference between a successful perforation and a dangerous misfire.

We were preparing for a conventional cased hole logging run, which involved wireline logging and perforating various zones in a deviated well. The logging cable was spooled up, the wireline truck prepped, and our cased hole wireline tools staged. Everything looked perfect on the surface. But as every wireline engineer knows, it’s the prep work that determines success downhole.

As I inspected the downhole tools and checked the wiring, I pulled out my multimeter to verify continuity and resistance across several connections. Normally, I’d use a blaster’s multimeter, which is specifically intended for working with explosives, but I was in a hurry and opted for an ordinary multimeter instead. A rookie mistake that nearly cost us.

For those unfamiliar with what is wireline in oil and gas, or why this matters, let me explain: Electrically initiated explosives, such as detonators and igniters, are frequently employed in wireline services for perforating guns. Using the wrong type of meter, especially one not designed for explosive environments, can send current through the circuit and unintentionally initiate a firing. That’s why wireline service companies train their crews to only use blaster’s multimeters with explosives.

Blaster’s meters are part of every complete wireline solution. They have ultra-low current output—safe for use around downhole pipe recovery tools, wireline perforating guns, and all types of firing heads. And when you’re dealing with complex wireline control systems in the cased hole logging service market, that safety margin is everything.

I caught myself just in time. The meter wasn’t connected yet. I swapped it for the correct blaster’s multimeter and restarted the checks: continuity, insulation, and resistance. It was a good reminder of why wireline courses emphasize safety, measurement techniques, and tool limitations. From formation evaluation to production logging and well integrity assurance, understanding tools like the megohmmeter and multimeter is critical.

Later that day, we used a megohmmeter to confirm the insulation resistance of our wireline tools. Megohmmeters apply high voltage—up to 1000V—to detect any potential insulation failure between conductors and ground. But here’s the thing: never use them near loaded perforating guns or any explosive component. It’s a tool meant for diagnosing insulation issues in wireline equipment, logging cables, and wireline control systems before you load anything hot.

In wireline well logging, a single broken insulator or shorted conductor can jeopardize everything—from cement bond logs (CBL) to fishing wire line equipment and even downhole camera operation. That’s why thorough checks matter, and why I always double-check the meter in my hand.

We wrapped up the job without issues. Perforations went off clean. The wireline unit functioned smoothly. The cement bond was firm. Looking back, that incident with the erroneous meter was insignificant, yet it stayed with me.  It was a reminder that in the world of wireline and perforating, mistakes aren’t always loud or obvious. Sometimes they’re quiet, like the click of a dial in the wrong direction.

So, to anyone starting into the wireline business, take your time, learn your skills, and never neglect the basics. Whether you’re out on a pump down perforating job or working with cased hole well services, whether you’re testing igniters or reviewing caliper log data, these subtleties are what keep your workers safe and your tools firing precisely when they should.

Because assumptions are not acceptable in our area of work. Only measurable decisions.