Every wireline engineer knows that cased hole logging is more than just a job—it’s an exercise in precision, patience, and sometimes, pure problem-solving.

I learned this the hard way during a caliper log job that started as routine but quickly turned into one of my most memorable downhole diagnostics experiences.

Setting Up for Success (Or So We Thought)

We were called out to a well where the client suspected casing integrity issues. The plan was simple: run a multifinger caliper tool (MFC) to assess casing ID, ovality, and any potential restrictions before deciding on further cased hole well services.

The wireline truck was in position, the caliper tool was rigged up, and the logging cable was tensioned properly. We had already pre-checked our wireline control systems to ensure smooth data transmission.

From the surface, it all looked perfect.

Then, we hit 3,000 feet, and things got interesting.

The First Red Flag: Erratic Data

As we passed through the first 500 feet of logging depth, the caliper log readings seemed normal. The pipe tally indicated consistent casing ID, and there were no major anomalies—until we reached 3,000 feet.

Suddenly, the borehole imaging software flagged erratic data points. The fingers of the caliper tool were bouncing excessively, showing inconsistent ID readings. At first, we thought it was just tool movement, but a closer inspection suggested something more serious—possible casing deformation.

Investigating the Cause

• Debris stuck in the wellbore? Possible, but unlikely, given the well history.
• Bad tool calibration? Unlikely—we had verified calibration before logging.
• Collapsed casing? A real possibility.

Instead of making assumptions, we pulled the tool up a few feet and activated the borehole imaging feature. This provided a 360-degree view of the casing. The results were clear—a restriction point was causing the erratic readings.

This meant two things:

• The well had mechanical deformation, likely due to overpressure or past workover operations.
• We couldn’t proceed without further wireline well logging to confirm the severity of the damage.

Making the Right Call

At this point, we had a decision to make—continue logging and risk tool entrapment, or reassess our approach.

We opted for a controlled pull-out to analyze the data further. After examining the caliper log, we confirmed an ID restriction at 3,020 feet with a 15% reduction in diameter. This was a serious casing integrity issue.

The client had initially planned for perforation services, but with the casing compromised, perforating guns were now out of the question. Instead, the focus shifted to remedial work, possibly a patch job or pipe recovery operation.

Key Takeaways for Wireline Engineers

This job reinforced several important lessons:

• Always verify your calibration. A bad caliper calibration can mislead you into thinking there’s casing damage when there isn’t.
• Use borehole imaging whenever possible. The ability to visualize restrictions in real-time saved us from making a bad call.
• Know when to stop. We could have forced our tool deeper, but downhole pipe recovery is never fun.
• Wireline control systems are critical. Monitoring logging cable tension and finger responses helped us detect issues before they escalated.

Final Thoughts

In wireline well logging, things don’t always go as planned. Cased hole wireline operations require engineers to think on their feet, trust their data, and adapt quickly.

That day, we didn’t just collect data—we helped the client avoid a major well intervention failure.

Another day, another lesson learned in the field.