Murray & Roberts Cementation was selected as the raise boring contractor for a new ventilation shaft at Ivanplats’ Platreef project. A 950-m-deep pilot hole had to be drilled to precise accuracy to allow for the shaft to be equipped with a hoist and rope guides to carry personnel.
The dual purpose use of the shaft required extreme pilot hole accuracy, which meant offering the client minimal deflection of the pilot hole using a continuous steering tool, explained Murray & Roberts Cementation senior project manager Dirk Visser.
“Using the well-proven German-designed and -manufactured Micon, Rotary Vertical Drilling System (RVDS), we were able to achieve the set parameters required for a rope guide installation,” says Visser. “The worst deflection was no more than 0.05%, or 452 mm, and by the time we bottomed out, the deviation was only 0.02%, or 226 mm, off centre over a final drilling depth of 950 m.”
Micon’s specialised RVDS is a continuous self-steering tool working on a close loop system which steers the tool using two-axis gyro inclination sensors which activate the hydraulic steering system. It can determine in real time if there is any deviation from the vertical course, and communicate this information to the operator on surface by means of pressure waves in the drilling water, whereby the pressure waves are converting into information through transducers.
Visser asserts that the drilling team not only ensured accurate directional results, but also optimised the performance of the RVDS by monitoring key variables such as voltage levels and water cleanliness.
He notes that Murray & Roberts Cementation has an established reputation for achieving high levels of accuracy in directional drilling.
EMAIL THIS ARTICLE SAVE THIS ARTICLE
To subscribe email subscriptions@creamermedia.co.za or click here
To advertise email advertising@creamermedia.co.za or click here
