MINERAL EXPLORATION
CE certified (Machinery Directive 2006/42/EC)
according to the latest EN16228 drill rig safety
standards available. When operating with the
Boart Longyear Freedom™ Rod Loader no
intervention is required from the driller’s
assistant to trip and align the rods or connect to
the top drive head. All operations happen safely
behind the control panel at the touch of a finger
for 100% hands-free rod handling.
Boart Longyear’s vast experience with coring
and drilling equipment comes from more than
127 years of proven performance and service in a
variety of applications. Strauss said that with the
company’s latest line of rigs and equipment, “we
have added technology to significantly enhance
safety, increase productivity, and improve ease of
operation and maintenance.” penetration rates reduce with depth, meaning RC
or RAB may become more economic with depths
over about 30 m. Sonic holes can be drilled dry,
but drilling fluids are required through significant
hard rock units and in deeper holes. “The main
drawback of the technique is the high relative
cost, being approximately three times the cost of
RAB, or one and a half that of RC. This said, sonic
can be ideal for remote areas where fixed
logistics costs are already high, exploration
seasons may be short lived and excellent
recovery and penetration rates are demanded,
such as at the platinum project mentioned. Sonic
is certainly not the answer for every project, but
it holds the potential of achieving results that
prove the feasibility of projects previously
unsampled or considered unviable.”
Sonic drilling – where does it fit? Through-bit logging
SRK Exploration Services (SRK ES) says it
realised the full potential of sonic drilling in 2010
when it recommended that sonic rigs should be
used at an alluvial platinum project that was
struggling to reconcile drilling results and mine
production. Oliver Bayley, Senior Exploration
Geologist at SRK ES: “Sonic drilling was ideal for
this project, returning excellent recoveries in soft
material while still being able to drill through
large boulders in the alluvial profile. All holes
were completed without refusal and the results
returned grades three times higher than the
previous (shell and auger) drill sampling, and
allowed the company to realise the full value
from its exploration results. Since then, SRK ES
used sonic drilling across a wide variety of
projects and developed extensive experience and
understanding of the advantages and drawbacks
of this technique.”
Sonic drilling is primarily used to sample cover
sequences, but unlike auger, aircore, RAB or RC
drilling, it can recover a continuous ‘core’ of intact
sample. Returning high quality samples from
near-surface unconsolidated or mixed materials
is sonic drillings’ main niche. “Coupling this
sample quality with the ability to drill through
hard capping rocks such as silcretes, basalt
flows, or large boulders, and return excellent
recoveries from underlying loose sediments,
makes it ideal for many placer deposits. SRK ES
recently recommended sonic drilling for a project
in Romania to evaluate dumps that not only
contain high grade slag and tailings, but
reinforced concrete and other rubble; it is
undoubtedly the best drilling technique to
sample such a mixed medium.”
Sonic drilling uses vibration (in the sonic
wavelength) of the drill string and drill bit for
penetration, with the driller aiming to achieve
maximum vibration (resonance) at the bit where
surrounding particles are either fluidised (in
loose materials) or fractured (in hard rock). High Where geophysical logging of cored boreholes is
required, be it in exploration, reconnaissance
drilling, groundwater or geotechnics, the
boreholes need to be accessible to the logging
sondes and carry minimal risk to their recovery. If
these conditions cannot be met, the use of a
conventional wireline logging winch may not be
practicable. One alternative is Through Bit
Logging (TBL). With this technique, memory tools
are conveyed through the drill pipe like a core
inner sleeve. The tool string is arranged so that
the sensors stick out through the diamond bit
and log the open hole as drill pipe is tripped out.
The approach adopted by Geovista, involves a
rig mounted depth measuring system, standard
logging sondes, a memory logging module, a
battery pack and running adapters. The latter
three items are designed to remain within the
core barrel, while the logging tools go through
the diamond bit, out in the open hole. The
running adaptor
allows for the tools to
be run in and
recovered, as one
would a coring inner
sleeve. The tools are
deployed only when
logging is required;
they are retrieved
when logging is
completed. The open
hole is logged by
pulling out drill pipes.
In this way, logs are
obtained more
quickly, and risk is
minimised since the
logging tools follow
immediately behind
the bit while being
pulled out along with the drill string. There is no
logging winch involved. The depth measuring and
32 International Mining | FEBRUARY 2018
recording device must be mounted on the rig, in
a way that would allow it to follow, unobstructed,
the travels of the drill head and keep track of the
current depth of the sondes in the borehole. A
tablet or a smart phone can be used to interface
wirelessly to both the depth measuring and
recording device and the downhole tool string for
the purpose of commands upload at the start, and
data download at the end of the logging operation.
The TBL memory module has sufficient capacity for
all logs and for the expected duration of most
operations.
“In addition to facilitating log data acquisition
in unstable, collapsing formations, the TBL
technique can be deployed to convey sondes in
highly inclined/horizontal boreholes. At its
simplest, it can also be used to cheaply check the
trajectory of boreholes in directed drilling. In
addition to the accessibility element, there are
also expected savings in time and logistics.
Intermediate logging runs can be performed
without the need to pull out all of the pipes.
There is no need to mobilise, rig up and rig down
a wireline logging system. Crucially, the same
probes can be used for both TBL and wireline
deployment techniques.”
Looking for gold while staying green
The growing number of environmental
restrictions and municipal regulations has left
drilling and mining companies alike seeking
ecologically friendly ways to deal with residues
and to reduce their water consumption. Fordia’s
customer, Alexandria Minerals Corporation,
researched the market to find a solution that
complies with environmental regulations, to be
able to continue drilling in a sustainable fashion.
Alexandria Minerals is a growth-oriented
Canadian gold exploration and development
Fordia developed a water treatment system
(WTS) for exploration drilling that is easy to
transport and easy to operate