#Diamond count run full#
#Diamond count run plus#

The most effective course of action is simply to forget about wasting time measuring additional stick-ups until after the bad ground is traversed and/or the mechanical problem is solved. So, faced with dire consequences for poor core recoveries and slow drilling rates, what does any good driller do?

Thus, it is more common to find that short runs are drilled because of bad ground conditions – and here is where the story gets interesting: Drill contractors are typically held to a minimum core recovery that is nominally upwards of 95%, to avoid a substantial penalty being levied by the client, hence it falls to the drill crews to ensure no such penalty is incurred, otherwise their bonuses are also in jeopardy.

#Diamond count run full#

Drillers and their crews use all their experience to keep producing full drill runs for as long as possible and hate delays, especially those caused by equipment failure. It could happen for quality assurance – to count the drill rods and confirm borehole depth – but the downtime involved eats into the drilling crew’s bonus, calculated on the basis of meters drilled per shift, so such interruptions are not welcomed. This combined length is then subtracted from the length of the drill string, being the distance from the cutting face of the drill bit resting on the bottom of the borehole, up to the relevant rod-join, and the result is the depth of the borehole.ĭone properly, this depth is accurate to the nearest centimeter, the calculations for which are recorded in a “Stick-up Log” (Fig 2), and the new borehole depth is also written on a core block, which is placed in the core tray at the end of whatever length of core was recovered from the drill run – even if no core was recovered.Īt this juncture, it is important to note that no driller stops a drill run short for a trivial reason. Hence, to find the new borehole depth, the distance from the relevant rod-join down to the datum – a distance that is colloquially called the “additional stick-up” – is measured and added to the “constant stick-up”, which is the fixed distance of the datum above the borehole collar (Fig 1). Note: A core barrel inner-tube normally has a +/- 15cm excess capacity, depending on how the inner-tube head is adjusted, to allow for an average length of stub to be picked up from the previous run.Ī SHORT DRILL RUN occurs when the core barrel inner-tube is pulled after a short borehole advance. At this point, a FULL DRILL RUN is achieved, and the core barrel inner tube is extracted, or ‘pulled’ to discover how much core was recovered from the advance. To make life easy for the driller, this capacity is designed to be slightly more than one, two, or three rod-lengths worth of core – so all the driller has to do is keep an eye on the relevant rod-join as the borehole is advanced, and stop drilling once this join is drawn down level with the driller’s datum on the rig (Fig 1).

To explain: A full drill run occurs once the driller has advanced the borehole by a depth equivalent to the capacity of the core barrel inner-tube. Although this may seem difficult to do, in fact it is a relatively easy task, so long as the driller adheres strictly to the definition of a drill run, being:Ī drill run occurs whenever the core barrel inner-tube is extracted after an advance, however short this may be.

Thus it is imperative to delineate these breaks and produce a ‘Core-Loss Log’ explaining the reason for each missing section.

#Diamond count run plus#

For example, many ores are associated with weak altered rock that could therefore be under-sampled, plus the viability of any deposit, or civil construction, depends on the degree of support required to stabilize the ground.

These core loss gaps result from difficulties with the drilling process, either due to poor ground conditions, or mechanical problems, and are therefore zones of potentially high economic and geotechnical risk. These provide detailed descriptions and analyses of the ground sampled from the recovered core segments, but rarely identify and characterize sections along the borehole where sample is missing. The data used to plan mine developments and major civil works are mostly derived from drill core logs.