Most Drilling Cost Discussions Start in the Wrong Place

When drilling costs increase, the first reaction on site is usually:

 “Bit price is too high”

 “We need a cheaper supplier”

 “Consumables are getting expensive”

This line of thinking focuses on unit price.

But in drilling operations, unit price is rarely the real cost driver.

The variable that silently controls drilling cost — yet is often ignored — is:

Tool Service Life

Not just how long a tool lasts in theory,
but how long it performs within stable drilling conditions.

 

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Service Life Is Not Just Wear Time

In field operations, a tool does not become “finished” only when it is fully worn.

A tool becomes uneconomical when it starts to cause:

 Penetration rate decline

 Instability (vibration, deviation, irregular hole geometry)

 Higher air or energy consumption

 More frequent stoppages for checking or replacement

So effective service life =
The duration a tool maintains stable drilling performance, not just physical survival.

Two bits with the same carbide grade can have very different economic results if:

Tool B often costs more per meter, even if it lasts “longer”.

 

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Why Service Life Directly Controls Cost per Meter

Drilling cost per meter is not linear with tool price.

It is driven by how service life affects the whole system:

1️⃣ Replacement Frequency

Short life → more tool changes → more non-drilling time
Every tool change includes:

 Machine stoppage

 Operator time

 Alignment re-adjustment

 Restart inefficiency

This is hidden time loss, not shown on invoices.

 

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2️⃣ System Stability

As tools degrade, instability increases:

 More vibration

 Irregular impact transfer

 Higher stress on hammer, rods, and joints

This leads to indirect wear on other components, multiplying total consumable cost.

 

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3️⃣ Energy Efficiency

A worn or unstable tool:

 Needs more air to maintain penetration

 Reduces impact efficiency

 Lowers drilling rate per unit energy

That means more fuel, more compressor load, higher operating cost.

 

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4️⃣ Hole Quality & Rework Risk

Unstable tools cause:

 Hole deviation

 Oversized or irregular holes

 Poor fragmentation or anchoring quality

Rework cost can easily exceed the price difference between tools.

 

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The Engineering Reality

From an engineering standpoint:

Drilling cost is controlled by performance stability duration, not tool purchase price.

The longer a tool can operate while keeping:

 Stable penetration rate

 Low vibration

 Efficient energy transfer

 Predictable wear pattern

the lower the true cost per meter.

 

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What Experienced Sites Measure Differently

Sites that successfully reduce drilling cost usually track:

 Meters drilled per tool under stable conditions

 Performance drop point (not just failure point)

 Tool behavior in specific formations

 Replacement interval predictability

They do not ask:

❌ “How cheap is the bit?”
They ask:
✅ “How long can this tool keep the system stable?”

 

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Tool service life is not just a durability metric.
It is a system stability variable.

And system stability is what controls:

 Downtime

 Energy use

 Secondary wear

 Hole quality

 Total cost per meter

In drilling, the cheapest tool is often the one that works steadily the longest — not the one with the lowest price tag.