We were working a deep lateral out in the basin. The frac crew was moving fast, everything running smooth on a cased hole wireline job. My team was setting up for a wireline perforating run, and I requested the base log depth to tie into.
The client handed me the numbers from a previous crew—looked solid on paper. But something didn’t sit right. We ran a quick gamma ray pass, cross-checked the marker joint, and sure enough… the log was off by nearly 7 feet.
That’s the kind of mistake that turns a clean perforation well into a mess—missed clusters, damaged zones, or a plug set in the wrong place.
From that point forward, we made it non-negotiable: every job starts with full base log correlation, aligned to our own systems and verified using approved points.
Why Depth Control Still Matters in a Digital World
Even with all the advances in wireline technologies, wireline control systems, and formation evaluation, there’s still no shortcut around a solid depth match.
A properly correlated base log is the foundation for:
- Plug setting
- Perforating gun deployment
- CBL logs
- Caliper logs
- Future pipe recovery or fishing wire line operations
- Well tie-ins for production logging services
Without it, you’re flying blind.
What We Check Before Logging Begins
Before we run any wireline well logging, we always gather and verify:
- Total well depth
- KB and GL (Kelly Bushing & Ground Level)
- Float collar and shoe depth
- Liner tops and DV tool locations
- Casing changes
- Known permanent markers (marker joints, casing collars)
- Casing weight and tally data
- Formation tops if available
This data doesn’t just give us a map—it allows us to challenge assumptions and validate against real, measurable tie-in points.
The Real-World Correlation Protocol We Follow
Whether we’re running horizontal wireline, plug and abandon, or high-pressure pump down perforating, we use the following steps:
- Measuring wheels and encoder systems must match the logging cable size
- Recent depth correction data from the line record book must be verified
- Use only scintillation-type gamma ray detectors for accurate readings
- Tie in at two or more points when possible—e.g., liner top and marker joint
- If correlation shift exceeds 2 ft per 1000 ft, stop and notify management
- All discrepancies must be resolved before any primary logging run begins
- Final pulled depth at surface must be within 1 ft per 1000 ft
- Record the correction (amount, direction, and correlation point) in the log header
- Save both the digital data file and printed log copy for future reference
We log every pass, on depth or not. That record becomes part of our integrity wireline archive for the life of the well.
Why It’s More Than Just a Step in the SOP
This isn’t just box-checking. In the wireline services oil and gas industry, correlation procedures protect:
- Your data
- Your tools
- Your time
- Your reputation
Get it right, and you’re aligned for success. Get it wrong, and you’ll be running a wireline truck to fix what should’ve been done before the first connection was made.
Lessons for Wireline Techs and Engineers in Training
If you’re learning through wireline courses or trying to level up inside a wireline service company, know this:
- Base log correlation is your first and last defense against misruns
- Don’t trust external data until you validate it
- The best wireline providers build their own baseline
- Proper correlation separates good jobs from great ones
Final Thought
In the high-demand world of cased hole logging, where pressure is high and every minute matters, correlation isn’t optional—it’s operational survival.