posted by Rod McCoremick, Blog author, Fordia Powered by Epiroc
August 2, 2021
Drilling parameters are really important when it comes to achieving great drilling performance and extended equipment life. While it is important to choose the right equipment, once drilling conditions change, you need to adjust your parameters to maintain good drilling performance. Understanding how to adjust drilling parameters can help drillers improve performance in difficult drilling situations.
Drilling parameters include the rate of penetration, the rotation speed, the water flow and the weight on bit (WOB) also known as feed pressure. All of these parameters work together to provide good performance. The gauges on your drill rig are there to help you monitor situations and adjust the parameters as needed.
There should be a minimum of three gauges on a drill rig: water pressure, feed pressure and torque pressure. They are integrated onto the control panel.
The water pressure gauge on the drill rig indicates the amount of pressure in the circuit. Beginning at the pump, the water flows through the high-pressure line to the water swivel, through the drill rods, past the bit, and unless lost to the ground formation, it travels back up the hole and out the casing back on the surface. Many things can affect water pressure including but not limited to, the ground formation, the gauge of your diamond tools, inner tube adjustment, condition of the drill rods, drilling techniques, type and size of coring system, etc. The water pressure gauge monitors these pressure changes, telling you what the in-hole pressure is. This pressure can be substantial (pressures can reach excess of 1000 psi) so these circuits are complete with a high-pressure relief valve or “Pop Valve” to protect the driller and helper against high pressure spikes while drilling
While you are drilling, you cannot change the water pressure – you can only monitor it, and you should be monitoring it closely. Water pressure is a telltale sign of what is going on down in the hole. For example, it it spikes, this is an indication that something is blocking the water from flowing. There could be a core block that is forcing the water shut off valves to push out and block the water flow. Of course, all of this only applies if you are drilling where there is water return.
The best way to manage your water pressure and avoid problems is to:
Torque pressure is the amount of force applied to make the drill string turn. As with the water pressure gauge, this is not something a driller can control, but only monitor. The torque pressure will also provide valuable information regarding conditions in the bore hole because when the ground changes, the torque pressure can change as well.
For example, if you are drilling and your torque pressure is 1200 when you suddenly hit a clay seam. The torque pressure will increase to say, 2000 because the clay is preventing the bit from turning freely and the drill string is labouring hard to maintain the rotation speed and push on the bit. Similarly, if you hit a void, you will see the torque pressure drop because there is no pressure on the bit while is in a void.
This gauge represents the hydraulic force being exerted on the drill bit as it advances through the rock, usually in pounds per square inch (PSI). Unlike the other two gauges above, the driller is able to control the pressure instead of only monitoring it. This value comes from the cylinder or cylinders that push the bit into the ground.
"Once you uderstand what the gauges on the drill rig can tell you and the type of information they provide, you will see how valuable they are."
Drillers should only apply as much pressure as is needed to cut the rock and advance in the bore hole. Applying too much pressure will wear down the drill bit. A lot of this will be at the discretion of the driller as he can choose to lean on the bit with extra pressure or keep the pressure slow and steady.
As you advance and go deeper into the bore hole the amount of feed pressure required will change. When you start drilling, you may have only 10,000 lbs of pressure but after 100 feet, you may have to reduce the pressure due to the weight of the rods that add to the feed pressure. In a deep hole, this added weight may mean that you have to hold back as you drill in order to compensate for the weight of the rods.
Once you understand what the gauges on the drill rig can tell you and the type of information they provide, you will see how valuable they are. Drilling parameters are all closely related so you must understand the relationship between them. Our free guide to drilling parameters can give you a lot of information. You can also contact our technical team, they have a lot of expertise and can guide you as you try to optimize your parameters.