Diamond Drilling Dictionary:
RPM: Rotation of the bit (Round Per Minute)
WOB: Weight On Bit (kN)
ROP: Rate Of Penetration (cm)
FLOW: Water flow (Liter Per Minute)
RPC: The ratio of RPM/ROP (Revolution Per Centimeter)
Successful exploration drilling results from a clear understanding and cooperation between two professionals, the Diamond Driller and the Geologist. Drilling operations are controlled by geologists but they lack the knowledge and experience to optimize the operation of the drill. The Professional Diamond Driller should not hesitate to share his knowledge to improve the operation. A professional diamond driller will adjust all these parameters matching the drilling condition.
Drilling Operation Parameters
Bits Type | Rotation(RPM） | WOB（KN) | Flow(LPM) |
B Size | 900-1500 | 15-30 | 25-35 |
N Size | 700-1050 | 20-40 | 38-48 |
H Size | 500-960 | 30-50 | 40-60 |
P Size | 400-750 | 40-60 | 60-80 |
ROTATION (RPM)
Rotation speed should be adjusted considering:
a. Diameter of bit
b. ROP
c. Depth of drilling
d. Deviation issue
e. Vibration of string rod
RPM too high with low ROP can cause polishing of the bit
RPM too low may result in faster wear of the bit
WOB (KN)
The weight on bit depends on rock and bit type, RPM, ROP and water flow.
Try to maintain a constant ROP by increasing or reducing the WOB. Always adjust the
hold back pressure while adding rods.
a.Best cost per meter
b.Smooth operation
c.Best bit life
d.Sharp bit
WOB | |
Too Low | Too High |
Premature wear of bit | Low productivity |
Rod and barrel damage | Risk of polishing the bit |
Hole deviation | Low bit life |
Premature wear of rig | |
WATER FLOW （LPM）
Drilling performance is directly related to the fluid flow over the bit, fluid flow has very important different functions :
a.Removing cutting
b.Cooling the bit
c. Lubricating the bit and rods
ROP
The rate of penetration is the key parameter during drilling.
It results from the right combination of WOB and RPM for a rock type and condition.
Well -maintained ROP ensures :
a.best cost per meter
b.smooth operation
c. best bit life
d.sharp bit
RPC
Revolution Per Centimeter is an indicator coming from
the division RPM / ROP
Example of an N size bit turning @1200 rpm
and run @15 cm/min
RPC = 1200 / 15 = 80
Maintain the RPC within 50 < RPC < 100
SHARPENING TECHNIQUES
a.Add WOB until torque rises, once ROP increases, reduce WOB to maintain desired ROP
b.Reduce RPM by half, wait until torque and ROP rise. Return speed to normal operation.
c. Reduce the water flow
DO
* Respect safety rules
* Wear proper protection
* Check rod thread from leaks (rod gage)
* Start fluid circulation before running the bit to bottom
* Starting a new bit, don’t go full ROP until you drill 20 cm
* Make sure the reaming shell is within gauge and out lasts the bit
DON’T
* Drop the bit
* Start rotation with WOB
* Collar the hole with new bit
* Put wrench on diamond portion
Note:
The information contained here provides the reader with suggestions and guidelines dealing with a number of hypothetical situations. CGEGTECH accepts no responsibility for damages, consequential or otherwise, resulting from application of such guidelines and suggestions. The reader is strongly encouraged to contact an authorized CGEGTECH representative to obtain guidance in dealing with specific real situations.
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