Drilling parameters play a large role in helping drillers achieve a good ROP (rate of penetration), superior drilling performance and long bit life. They are basic recommendations that help guide a driller avoid burning bits or damaging other drilling equipment. Keep in mind that there is a relationship between the drilling parameters and all others factors in drilling, such as the diameter of the equipment of you’re using, rock hardness or ground variability. Understanding how to adjust drilling parameters can help drillers improve performance in difficult drilling situations. We’ll look at a few of them here.
Rotation speed should be chosen carefully based on the diameter of the system you are using. Many factors can affect the choice of the speed of rotation. These factors include penetration speed, diameter of the bit, depth of the hole and level of vibration.
If you are penetrating the rock quickly, it is possible to rotate the rods faster which will improve your ROP. If you are having difficulty penetrating the rock, you can reduce RPM to help increase ROP. The RPM must be measured using a tachometer. If the RPM is too high in relation to the weight on bit, this can cause polishing of the bit. On the contrary, if the RPM is too slow, this can cause premature wear of the bit.
Weight on bit
Bit pressure, or the force applied on the bit must be as low as possible while maintaining a good penetration rate. You should put only as much pressure on the bit as needed to advance. To achieve a good penetration rate you must aim for the ideal combination of rotation speed and bit pressure.
This relationship will change as you add each rod. It is important to keep sufficient speed of penetration in order to prevent the polishing of diamonds. The consequences of pressure that is too high include premature wear of the core bit, overexposure of the diamonds in the bit, wear on the mechanical components of the drill, the rods and the core barrel, and greater probability of hole deviation. Get this guide to see charts on bit pressure.
The water flow should be as high as possible but must be related to the bit size and type of rock to be drilled. This guide provides charts. In a very hard and competent rock, where the speed of penetration is low, the water flow must be reduced to enable the cutting of the rock and diminish the risk of polishing the diamonds.
Always make sure there is proper and sufficient water flow to the bit. A check that your rods don’t leak is suggested. Check for leaks in the system including pressure pump, water lines, manifold and most importantly drill rods. A leak test should be done periodically on your drill rods to make sure you are not losing flow over several joints in the hole.
Some core bits allow drillers to adjust drilling parameters more liberally. We’ve just launched the RockStar 9 core bit at this week’s PDAC and it’s a bit that provides a lot of versatility. By adjusting drilling parameters, the RockStar 9 allows drillers to increase penetration rate without sacrificing bit life. Our tech team is always ready to demonstrate new products and help drillers’ performance so don’t hesitate to contact them.