Shelton Drilling

Mud Drilling vs. Percussion drilling

Mud Drilling or mud rotation drilling is a drilling method where water is used to remove the overburden or cuttings.

This method is normally used where water is present in the formations before the rock layer and very often in conditions where clay is present.
“Mud pits” are usually dug in the garden and filled with water. The water is then thickened using additives and is then pumped through the drill bits into the borehole. This thickened water helps to stabilize the walls of the borehole and assists in moving the cuttings (material) to the surface.

Percussion drilling (drilling with air) is when compressed air is blown down the hole and the overburden or cuttings are expelled.

Steel casing is seated onto the bedrock and the hole is then drilled through the bedrock. A compressor with a range of between 10 and 21 bar is used for this application.

Both methods can be used when drilling the same borehole, the trick is just to recognize when to stop with percussion drilling and switching over to mud rotation.

If you are starting with air and the formations below become too wet and muddy then its time to change over to mud rotation.

You may have to switch drilling methods again once you have reached bedrock, if the water that you are trying to get to is in the bedrock. In most cases with mud rotation drilling the water may be found in a layer of decomposed sandstone and this water is lying on top of the bedrock. High Steenberg and some areas in Tokai, Lower Constantia and Claremont have these formations/characteristics. I know as we have drilled a number of holes in these areas.

Failing to recognize the formations whilst drilling will result in the compressed air blowing mud over the property and possibly creating a cavity below the surface. The hole may not be stable long enough to install the steel casing and seating this in the bedrock and therefore successfully completing the drilling process.