1(^6 4)
5
2
3
8
9
7
24 DISCOVERMAGAZINE.COM
TO
P:^ B
AN
KS
PH
OT
OS
/IS
TO
CK
.^ BO
TTOM:^COLO
RA
DOPLATEAU
GEOSYSTEMS^ INC.sand particles their spherical shape. (Under a micro-
scope, they’re clearly rounded, but they’re not perfect
spheres. To human eyes, though, they don’t look or feel
that different from regular beach sand.)
Quartz’s hardness and uniformity make it ideal for
use in fracking. That basic process involves drilling
a borehole into the ground, first vertically and then
horizontally along a layer of shale. After a steel pipe
is inserted, cemented into place and perforated in
the target spot, the hole is pressurized by injecting a
combination of sand, water and chemicals. The intense
pressure fractures the surrounding shale; it’s through
those fractures that oil and natural gas can flow back
up to the wellhead, along with some of the water and
chemicals originally used to pressurize the borehole.
When the initial pressure that caused the fractures
is removed, sand is what prevents those cracks from
collapsing, essentially propping them open. It’s one
of many proppants, and it can resist the intense pres-
sures at those depths — withstanding pressures of
over 5,000 pounds per square inch before it crushes,
sufficient for most fracking jobs.
Fracking operations can use other materials as
proppants, such as ceramic particles or broken-up
walnut husks. But Ron Dusterhoft, a technology
fellow at Halliburton, says sand is better these days
mainly because it’s cheaper and gets the job done,
even though the manufactured proppants are
generally stronger.
There are other sources of sand across the country,
most notably in Texas, whose sand is often referred to
as “Texas brown sand” in contrast with the “northern
white sand” mainly from Wisconsin, Minnesota and
Illinois. The darker color of the Texas sand is due to
impurities — minerals besides quartz — which render
it weaker than the purer sand.
Some companies use Texas brown sand because it’s
closer to the wells where fracking is occurring, thus
saving money on transportation while still getting
sufficient results in less demanding mines. But in
terms of purity and crush strength, Wisconsin’s sand
is hard to beat.NOTES FROM EARTH
Sand Mine Steps
- Clear any
existing vegetation. - Remove the topsoil
and any rock that
stands between you
and the sandstone. - If the sandstone
is really hard, use
explosives to bust it
into smaller pieces
before scooping it
up with excavation
equipment. - Haul the sandy
hunks to the crusher,
where they’ll be
pulverized into sand. - Wash the sand
with water to remove
silt and clay, and with
flocculants to remove
particles too fine
for fracking. - Stockpile clean,
wet sand over drain
tiles to collect water
for reuse. - Send wastewater to
holding ponds where
particulates settle out. - Dry particulates to
use as backfill or sell
as industrial sand. - Backfill.
There’s a reason these fracking sands are reminiscent of a
nice beach: Wisconsin used to be one 500 million years ago.
Source: Wisconsin Geological & Natural History Survey