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>Comparative table between Coring and Reverse Circulation method

Comparative table between Coring and Reverse Circulation method

 

Core drilling method

Reverse circulation drilling method

Application


Used for very precise sampling where the stratigraphy and analysis of veins are important.

Used for bulk commodities where a broad definition of the body and where ores and geochemical analysis are important.

Sample


The analysis can be done directly on site because the sam- ple is intact grains and veins are visible, ability to record the orientation of the sample and survey the hole.

Sample weights of the cuttings; opportunities to analyze the larger cuttings; monitoring survey possible.

Drilling rate

Slow forward speed, can vary considerably depending on ground type but generally 25-30m per shift.

.

Rapid penetration, can vary considerably depending on ground conditions and depth of the hole, but usually 200m per team.

Depth capability


Beyond 3000 m with large capacity machines.


Maximum 800m with the biggest rigs and high pressures using air booster.


Hole diameter


46 to 146mm, depending on the tools used.

89 to 146mm, depending on the tools used.


Flexibility

Ability to select tools for a variety of rock and soils forma- tions, including an undisturbed sample in unconsolidated and sedimentary coal applications.

Limited to consolidated formations where open hole drilling is possible.

Cost

Low initial investment, but generally more expensive to me- ters drilled because of the limitation of the speed.

Higher initial investment but this drilling method is faster and therefore the price meters drilled is more interesting.