The Ko Ko Trainer

Read a well log in five minutes. Six patterns, taught to me years ago by a mentor named Ko Ko Kyi, drilled into your hands in one short run.

Three levels

01The patterns. Four curves, left or right. Learn the six calls.

02Real log strips. Same calls, now on a noisy triple combo.

03The exceptions. Where the rules break, and careers are made.

New to this? The rules come from my 2017 article, How to easily read a well log in 5 minutes. You can also skip straight to the .

Fair warning: this drills the pattern-recognition layer only, deliberately simplified. The rest of interpretation (corrections, calibration, core, pressures, tests) still needs you.

Keys 1–6 answer · Enter for next

Run complete

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Patterns

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Log strips

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Exceptions

Take the cheat sheet with you

One page: the six patterns, the exceptions, the scale conventions. Drop your email and it's yours, plus an occasional petrophysics note from me. No spam, unsubscribe any time.

The six Ko Ko rules, one page

Curve order: gamma ray · resistivity · density · neutron. L = deflects left, R = deflects right.

Pattern	Call	Why
R·R·R·R	Tight non-reservoir	Everything right. Nothing to hold, nothing to flow. Move on.
R·R·R·L	Shale	Neutron flips left: clay-bound water. The reversed density-neutron separation is the shale signature.
L·R·R·R	Tight reservoir	Clean rock, no porosity. Reservoir on paper, not in practice.
L·L·L·L	Water	Clean, porous, conductive. Salty water talks to the resistivity tool.
L·R·L·L	Oil	Clean and porous, but resistivity stands alone on the right. Hydrocarbon does not conduct.
L·R·L·R	Gas	Like oil, but neutron swings right. Fewer hydrogen atoms: the classic crossover.

Where the rules break

Low-resistivity pay. Laminated sands and conductive clays drag resistivity down over real oil. Check thin-bed logs, core, and test data first.
Fresh formation water. Fresh water barely conducts and mimics oil. Know your water salinity before you trust rule five.
Hot sands. Feldspar, mica and uranium push GR up in clean sand. Spectral GR separates minerals from clay.
Organic-rich source rock. Kerogen is light and resistive, faking an oil-sand response. Unconventionals need their own toolkit.
Thin beds. Standard tools average over about a metre. A 40 cm sand smears toward shale and may still produce.

Scale conventions

GR: 0–150 API, increasing right.
Resistivity: 0.2–2000 ohm·m, log scale.
Density 1.95–2.95 g/cc with neutron 45 to −15 pu on a compatible scale, overlaid in one track.

Deliberately simplified. Real interpretation adds environmental corrections, calibration, core, pressure and test data on top of these patterns.