I still remember the pit in my stomach when I heard the words: “You’re off depth.”

We were halfway through a multi-stage horizontal wireline job. Everything had gone according to plan—at least we thought so. The wireline truck had been running smooth, the logging cable had passed all checks, and our wireline control systems were giving clean diagnostics. But when the pressure dropped after the perforating gun fired, it didn’t match the formation we were aiming for.

Sure enough, we’d perforated too shallow. The gun fired exactly where it was built to—but not where we thought it was built to. Turns out, the issue wasn’t in the wiring or the firing head. It was in the labeling.

Back then, we didn’t have a clear SOP for marking the top and bottom shots on our perforating gun assemblies. And that one oversight led to a missed target, extra rig time, and an awkward conversation with the company man.

Since then, marking our perforating gun assemblies has become sacred ground for me. Every tool I send out now has clear, painted rings that scream “TOP SHOT” and “BOTTOM SHOT,” aligned with the scallops on the charges. We use grease pencils and paint markers—whatever it takes to make it obvious.

And when it comes to blanked sections? Those get marked just as clearly. “BLANK” labels go opposite the painted rings so there’s no second-guessing during rig-up or while reviewing the string on-site.

For those in the wireline business, this is the kind of mistake that only has to happen once. It’s why I talk about it so much in my wireline courses. These aren’t just “nice-to-know” procedures—they’re critical. Whether you’re doing pump down perforating, traditional cased hole logging, or production logging services, your shot placement can make or break the entire operation.

There’s a lot of technology in our work. Wireline technologies have evolved fast—downhole cameras, digital logging cable, pipe caliper tools, tracer tech—but there’s no substitute for field-level clarity and communication. Marking your perforating gun isn’t glamorous, but it’s one of the simplest ways to ensure integrity wireline operations from start to finish.

The job where we misfired taught me something else, too: charged sections should always be loaded as close to the bottom of the perforating gun assembly as possible. It helps ensure you reach maximum depth. Especially in tight formations where every inch counts, that bottom charge placement could be the difference between solid productivity and a failed zone.

Now, when we ship out wireline perforating guns, every single one carries all the necessary information—UN numbers, EX numbers, shipping labels, and markings that comply with transportation regulations. These little details don’t just keep us compliant—they keep us safe and efficient. In the fast-moving wireline services oil and gas market, it’s details like these that separate top-tier wireline service companies from the rest.

So if you’re out there in the oil field wireline world—whether you’re running a wireline unit, overseeing wireline equipment, or just getting started with wireline well logging—take a moment to check your assemblies. Label everything. Paint the rings. Write the shot markers. Educate your team.

In wireline and perforating work, there’s no room for guesswork.