J&S Drilling has completed drilling and installation of dewatering bores at an open cut coal mine within the Bowen Basin. The purpose of the bores is to dewater the open cut pit. Allowing mining operations to extend further to expose and mine more coal product.
The scope of works comprised of 2 dewatering bores to depths of 215m and 223m below ground level, to the base of the coal seam.
Ground conditions in this area are renowned for being difficult to drill. With quartz and conglomerate lithology generating high rotation torque and difficulty clearing drill cuttings. Therefore J&S Drilling utilised 2 compressors, delivering 500psi/ 2200 cfm. In combination with a stiff foam mix of Superfoam and Liquid Polymer. As a result, the approach allowed for maximum up hole velocity to alleviate any issues with the clearing of drill cuttings. Thus, advancing the bore hole to the required depth.
The 8 5/8” production casing was installed using a rated casing knuckle attached to the drill rig head. This lowered the casing into the hole while making connections using the drill rigs rotation. J&S Drillings new JCB telehandler made its maiden voyage on the project and this was utilise to load the steel casing in the work area. The telehandler allowed for minimal manual handling and was an asset during the installation process.
The dewatering bores were constructed as per the ‘Edition 4 – Minimum Construction Standards for Water Bores in Australia’. 5mm bulker bags of gravel pack are used to fill the annulus around the stainless-steel screen and slotted 8 5/8” casing. The bulker bags were safely lifted using the JCB telehandler. Bentonite pellets are used above the gravel packed zone to seal the borehole and prevent grout slurry entering the gravel packed area. A 5% bentonite/ cement grout mix is used to finalise the installation back to surface level.
Both bores were air developed with the drill rods and jetting tool. The jetting tools allows for direct air to intrude the bore screens and slots in attempt to bring in all fine material, allowing for maximum yield.
A Fraste FS400 drill rig was utilised with an 8×4 MAN with 8000L water capacity, 2x drill compressors and a JCB telehandler.
Both bores are a great success and has since prompted request for another bore and potentially more in the future.
