ago, I never imagined that my precious collection of vinyl records would become
essentially obsolete. But I was excited about the advent of 8-track tapes. I
could then play music of my choice while driving! Then cassette tapes replaced 8-tracks.
CDs, then DVDs, came along to make those conveniently smaller cassettes
the thought of 8-tracks and cassettes as advanced technologies is laughable, at
least to those who even remember them. Now, all that is needed to listen to
music or other audio recordings, or to watch movies or sports, is a cell phone,
tablet, or laptop computer. So, could something as standard in the oil and gas
industry as sand proppant for hydraulic fracturing—that seemingly has no need
to be replaced—become obsolete in favor of an improved “technology?” It may
seem unimaginable, and maybe it won’t happen anytime soon, and surely not all
at once. But it is conceivable, and perhaps it should happen.
has long since been the preferred and most abundantly used proppant in
hydraulic fracturing because of its availability in large quantities and cheap
cost. Its only application limitation is in wells with fracture closure
stresses above about 6,000 psi. For higher closure stress wells, higher crush
strength proppants, such as ceramics, are needed. There are also other specialty
proppants that are alternatives to sand, but they cost substantially more. So, they
are not realistic replacements on a significant scale. Sand really has no
competition for applicable wells, and most wells can be fractured with sand as
sand has issues. Sand for proppant comes from mining,
which is not an especially environmentally favorable operation, with respect to
carbon emissions and the eventual need for land restoration. Sand mining also
uses copious amounts of water, primarily for cleaning to remove contaminants
from the sand. Such substantial water usage requirements can, at least in proximity
of certain mining locations, impact water supplies for household use, farming,
ranching and wildlife.
the proliferation of hydraulic fracturing, especially in the exploitation of
unconventional resources, which calls for multi-zone fracturing treatments in
long horizontal wells, there are more frequent sand supply shortages and delivery
delays, if not outright unavailability from time to time.
not all sand is the same. Depending on the source, sand quality can vary.
Roundness, crush strength, presence of fines, etc., are not all the same from
one sand to another. Sand itself, regardless of quality, is abrasive and
therefore rough on fracturing equipment. Handling of sand can also be
problematic, given the potential for worker exposure to silica dust, which can
there a realistic alternative to sand? If there is a
realistic alternative, it would have to be competitive in cost, with equal or
superior properties. It’s difficult to imagine, but there may be one on the horizon—oolitic
aragonite. Oolitic aragonite, or oolites, are egg-shaped particles that form in
agitated shallow-marine waters in tropical settings that are saturated with
respect to calcium bicarbonate. Carbon dioxide is lost to the atmosphere
through degassing as a result of agitation, through elevated temperatures from
solar radiation, and the activity of photosynthetic organisms. The loss of carbon dioxide results in precipitation of concentric layers of calcium carbonate in the form
of microscopic layers of interlocking crystals on pre-existing skeletal or
particles formed this way are composed of highly pure calcium carbonate, with
unique physical properties. When dried, these particles, comprising
interlocking networks of needle-like crystals, form a highly porous substrate
capable of imbibing liquids. Once many layers of calcium carbonate form, the
oolitic particles become dense and fall out of suspension. In areas where
conditions are right, a ridge of sand-like material will form and extend for
more than 50 mi. For example, throughout the Bahamas, more than one billion
metric tons of material accumulate through this process, making oolite
aragonite actually sustainable, and one of the few renewable minerals in the
explanation and description of oolite aragonite comes from the company Pisa
Carolina, which supplies oolites for many different industrial applications,
including agriculture, construction, aquarium and aquaculture, water treatment,
horticulture, cosmetics, food, and pharmaceuticals.
addition to those industries, and given its properties, oolite has application
in the oil and gas industry as a proppant, and with the product name, EnviroProp.
So, what are the advantages of oolite relative to sand?
there are many potential advantages of oolite, as EnviroProp, if this naturally
occurring and renewable mineral can be supplied on a scale large enough to
serve as a relatively low-cost proppant in hydraulic fracturing – and ultimately as
a replacement for sand, the old standby. For this purpose, there is, or should
be, an increasing desire for a superior alternative at a similar cost and
overall lower cost when considering the associated supply and frac site
expenses associated with sand. WO
LEONARD KALFAYAN is recently retired, following over 13 years with Hess as Principal Advisor, Production Enhancement, and Head of Production Engineering and Stimulation. He has 42 years of global experience in the oil, gas and geothermal industries, primarily in production enhancement, new technology development and implementation, technical support and business development. Prior to joining Hess in 2009, he worked for Unocal, BJ Services, and as an industry consultant. He is a past SPE Distinguished Lecturer and SPE Distinguished Member. He has authored over 30 SPE and other journal publications and holds 13 U.S. patents. He also is the author of the book Production Enhancement with Acid Stimulation (in its 2nd edition), co-author of the book The Energy Imperative, and co-editor of the SPE Monograph: Acid Stimulation.