Pressure Limits Aren’t Suggestions: The Day I Almost Blew a Seal

Posted on by Crissa Fel Tawadan

We were midway through a high-pressure cased hole logging job on a tight horizontal wireline schedule. The rig was hot, the wireline truck was parked in place, the logging cable was threaded through a full stack of pressure control equipment, and the tools were ready to drop.

But then I overheard something that made me freeze.

“Hey, isn’t this line rated for 5,000 psi? This well’s at 5,000 too—it should be fine.”

Wrong.

It took everything in me not to lose it right there. That’s one of the biggest mistakes I see out in the field—confusing working pressure with wellhead pressure, or worse, thinking it’s okay to run wireline services at the full limit of the wireline equipment rating.

Here’s the deal—and this is what I drill into every one of my wireline courses:

Working pressure is the maximum the equipment is designed for. That number should never be touched during operations.

For example, if you’ve got pressure control gear rated for 5,000 psi, that doesn’t mean it’s safe to run at 5,000 psi. That’s your working pressure (WP). The maximum allowable operating pressure (MAOP) is actually 80% of that—4,000 psi in this case.

And when you test that equipment, you’re not just shooting for 5,000 psi. You’re running a test pressure (TP) at 1.5x WP, or 7,500 psi in this case. That’s how you verify the integrity of your wireline tools, seals, and body housing before sending it out to a high-risk perforation well job.

I’ve seen wireline service providers confuse these numbers and end up damaging downhole tools, blowing seals, or worse—triggering a release that leads to costly downtime and even fishing wire line scenarios.

We also calculate maximum anticipated surface pressure (MASP) and maximum potential wellhead pressure (MPWH) to estimate the worst-case pressures from either the formation or any induced pressure from surface pumping. From there, we run a well site test pressure (WTP) at 1.2x that estimate—but always make sure the WTP doesn’t exceed WP.

That’s how you stay within safe operating boundaries.

If you’re out there managing wireline control systems, perforating services, or even basic production logging, these numbers are more than just tech talk. They’re the rules that keep your wireline unit, your team, and your client’s well safe.

Here’s What I Teach My Crews:

  • WP = The maximum pressure rating. Never operate near it.
  • TP = 1.5x the WP. Used to qualify the equipment before the job.
  • MAOP = 80% of WP. Your true limit during live operations.
  • MPWH / MASP = Predicted highest pressure the well may produce.
  • WTP = 1.2x the MPWH—but still must stay below WP.

So, on that job where someone thought 5,000 psi WP meant “go for 5,000″—I called a time-out. We recalculated pressures, confirmed that our BOP, grease head, and lubricator were up to spec, and held the pressure test for 15 minutes per standard.

Because in the wireline oilfield, you don’t just play with numbers. You live by them.