Learning Centre – Nickel Shear Drilling
Today, we’re going to be discussing nickel shear drilling.
Let’s get right to it!
Nickel drilling is slow and requires a lot of patience – Drilling is preferably commenced with a HQ sized hole and regularly reduces down to NQ and even BQ as a last resort to counter the challenging, reactive ground conditions that usually accompany Nickel drilling.
To achieve the best results, we get back to basics and begin with purpose-built mud-mixing tanks and a solid drilling fluids program tailored to suit the expected challenging ground conditions in which Nickel is normally found. Without these the odds of successfully completing a drilling campaign in Nickel are slim. The drilling fluids program when drilling Nickel must be followed religiously.
Each Nickel program is essentially risk assessed, and each hole is meticulously planned to ensure completion in a timely and cost-effective manner. Drilling Nickel requires tremendous patience. There are no taking short cuts as drilling equipment and more importantly holes can be lost in an instant. Drilling Nickel requires a certain skill set and mindset that is acquired over time that not every driller will attain this over the span of their career.
Because of the naturally pressurizing and reactive nature of the formations in which Nickel is commonly found, drilling methods must be altered and veer away from the norm and standard drilling principles that you may expect to see on a drill rig in gold country.
Water, being the main variable needed to be to diamond drill is essentially the main ingredient which works against the driller in what is called shear zones. This is where the drilling fluid product selection and application is so important.
Given this progress can be extremely slow and metres limited. In some instances, the pressures down hole can be so great that progress can be lost and the rod string pushed back up the hole with the hole subsequently caving in.
In these cases, we adopt our fine-tuned grout and advance methods where we use cement to stabilize the area in the drill hole that is reactive and has stopped us advancing with the traditional core barrel. The cement helps with holding up the hole integrity when its drilled back through and seals up fissures in the ground so drilling fluid can’t escape into the formation causing the reactive ground to squeeze.
With nickel shear drilling, you can go through the first couple of hundred meters of a hole quite good, then you hit a zone that is pressurized and once you can advance anymore, the team will come back and cement that section up. These are the areas that if advanced through successfully, casing off is considered and the hole size potentially reduced to remove that area from having any further ill effect on drilling operations.
Sometimes you can advance 9 metres, sometimes it’s a meter and half. Sometimes its 30m pass the grout job but sectional grouting is quite frequent. You can only drill what the ground will allow. Nothing should be pushed. Grouting when required will pay off in the long run, this has been proven time and time again.
Traditionally cement or grout requires a minimum of 18 hours to cure. To prevent any client related downtime we will, if possible, drill multiple holes at once and cycle through them as we grout and advance each hole when we hit a shear zone. This will allow us to continually advance drill holes without costly standby delays.
To grout, we use a grout displacement plug – some people call the darby plugs, and they pump the column of cement down the rods with water behind the plug, and that puts the cement into the zone.
So that’s it for Nickel Shear Drilling and hope you found that helpful.
Feel free to reach out to us if you have any more questions.
That’s a wrap!