Some jobs stick with you—not because of what went wrong, but because of what had to go exactly right. This one wasn’t your typical wireline and perforating run. This was a full-blown TCP (Tubing Conveyed Perforation) operation where wireline logging simply couldn’t reach, and we had to adapt.

It was a horizontal well, deep into a shale formation. We’d already completed most of the stages using wireline perforating with standard pressure control equipment and a well-coordinated frac schedule. But when it came to the toe stage, we hit a wall. The wireline truck couldn’t make it past the kickoff point, and the deviation was too aggressive to push down even with a slick horizontal wireline setup.

This is where understanding both what is wireline in oil and gas and when to switch to tubing conveyed solutions becomes critical.

We went with TCP because the pump-down option wasn’t viable. There was no fluid exit path yet—no perforation well in place for flowback. So, it was time to rig up a TCP string using straight tubing and a pressure-activated firing head. TCP isn’t as common as wireline in some fields, but in cased hole solutions where access is limited and temperature extremes are in play, it’s a trusted method.

The prep was meticulous. We calculated hydrostatic pressure using the fluid weight and true vertical depth—critical for knowing when those firing heads would shear. In TCP, you don’t rely on real-time feedback like wireline services do with logging cable and surface readouts. Everything needs to be calculated, prepped, and pinned before the guns go downhole.

Our gunstring used pressure-activated firing heads with staggered shear pins and time-delay fuses. The goal was to fire from the bottom up, using delays to move between zones. That’s where your understanding of differential pressure and formation evaluation comes into play—small missteps in calculation can lead to misfires or unexpected initiation.

As we ran the guns in hole, we carefully monitored induced surface pressure. Circulating during RIH (run in hole) was limited to under 1,000 psi to avoid accidental gun initiation. That’s one of those TCP safety lessons that complements what we teach in wireline courses—always treat every system like it’s live.

Once at depth, we started the pressure ramp-up. There were no digital readouts or caliper logs to guide us—just a pressure gauge and years of field experience. We crossed the shear threshold, and sure enough, the first gun fired. No loud noise. No jolt. Just a slight drop in surface pressure and the satisfaction of knowing we’d hit the mark.

Then came the waiting game. We moved the tubing to the next interval and let the time-delay fuses work their magic. One by one, each perf gun activated. A clean, calculated cascade of perforations through the toe stage. No misfires. No overpressure events. Just a successful bottom-up TCP firing sequence.

After waiting the full safety period, we pulled out of hole slowly, assuming every gun was still live. That’s something every wireline provider, from small wireline service companies to the big names in the wireline services market, preaches—treat every pull like it’s loaded. Whether it’s wireline well logging or TCP, safety isn’t optional.

Once at surface, the crew broke the guns down with full PPE, checking for pressure traps and inspecting every sub. We documented every connection, checked every detonator, and logged everything. That kind of attention to detail is what sets integrity wireline operations apart from risky shortcuts.

This job reminded me that wireline technologies and TCP aren’t competing—they’re complementary. In some wells, wireline tools are the best fit. In others, like this one, tubing conveyed options offer the only safe, effective path forward.

So if you’re new to this business, or thinking about expanding your knowledge beyond standard wire line services, learn about TCP. Take those wireline courses. Understand the theory behind cased hole logging and firing systems. Because in today’s oilfield services company landscape, versatility is the difference between just finishing a job and nailing it.