This case explains how wear behavior directly influences penetration rate, energy transfer, and overall drilling cost.

Project Background

lRock Type: Abrasive formation with high silica content

lDrilling Method: Down-the-Hole (DTH)

lOperational Goal: Maintain stable penetration and tool life under high wear conditions

lObserved Issue: Rapid performance decline despite stable drilling parameters

Initial evaluation showed no major change in feed force, air pressure, or rotation speed, yet drilling efficiency decreased progressively.

Field Observation

During drilling operations, the following patterns were identified:

lGauge buttons experienced accelerated wear

lCutting structure became rounded rather than fractured

lIncreased vibration occurred as contact geometry changed

lPenetration rate dropped over time without operational change

Although tools remained operational, effective rock-breaking efficiency reduced as wear progressed.

Wear Mechanism Analysis

In abrasive rock, wear is dominated by:

1. Abrasive sliding wear

Hard mineral particles grind against carbide surfaces, gradually removing material.

2. Edge rounding of cutting structures

Sharp impact points become smooth, reducing stress concentration and rock fracture efficiency.

3. Energy dissipation through friction

Instead of breaking rock, part of the impact energy converts to heat and vibration.

As wear progresses, more energy is lost, and less is used for effective rock fragmentation.

Impact on Drilling Efficiency

The change in bit geometry leads to:

lLower penetration rate

lHigher specific energy required per meter

lIncreased mechanical stress on the drilling system

lMore frequent tool changes

Even if unit price and initial performance appear acceptable, progressive wear significantly raises cost per meter.

Engineering Insight

Drilling efficiency is not only determined by impact energy or rotation speed, but by how effectively the tool maintains its rock-breaking geometry over time.

Tools designed with:

lBetter wear resistance

lStable carbide support

lOptimized gauge protectionretain cutting effectiveness longer and sustain higher drilling efficiency in abrasive formations.

This case demonstrates that in abrasive rock, bit wear mechanism directly controls drilling performance and operational cost.

Understanding how wear alters energy transfer and cutting geometry allows better tool selection and improves cost efficiency through longer effective service life.