nearby wells or from the targeted for-
mation itself. CCNG is very dense and
can be pumped like a liquid.
The CCNG is pumped to high pressure with a cryogenic natural-gas pump
and then vaporized via heat exchangers into high-pressure compressed
natural gas. It is then blended with a
proppant-carrying slurry and foaming
agent and sent down the well.
This process creates, extends, and
holds open ;ssures in the underground
formation. When the pressure is reduced, the proppant holds open the
;ssures, releasing oil and gas.
“Instead of relying on complex chemistry like water-based fracturing does,
VRGE relies primarily on mechanical
processes such as CCNG production
(compression and refrigeration), cryogenic pumping, slurry blending and
pumping, and ;uid phase shifts,” said
Jeremy Dockter, co-founder and managing director for Expansion Energy.
“By using a hydrocarbon to produce
a hydrocarbon,” Dockter continued,
“VRGE avoids the need for most
chemical additives and biocides. Other
gas-energized technologies, like CO2
and N2, introduce non-hydrocarbon
substances into the product stream,
which then must be captured and re-
moved, driving up costs and adding lo-
gistical complexity. With VRGE, once
the well begins to produce, the natural
gas simply returns to the surface via the
wellbore and can be sold to the market
Overall, Expansion Energy says its
VRGE process can reduce total com-
pletion costs by as much as $2 million
per horizontal well versus standard wa-
Praxair, a supplier of industrial gases
based in Danbury, Conn., has developed a system that relies on a di;erent
lique;ed gas. Its DryFrac technology
relies on liquid carbon dioxide that is
mixed with sand and sent down the
hole under high pressure.
The CO2 can also be captured as it
returns to the surface.
A key challenge that Praxair solved
with this technology is the ability to
blend the lique;ed carbon dioxide and
sand at precise concentrations, customizing it to the shale formation being
fractured. Carbon dioxide is delivered
and stored on the well pad. DryFrac
blenders are delivered to the site with
the blender vessel in a horizontal position, which is then hydraulically lifted
to the vertical operating position and
locked in place.
“Once all the piping to and from the
blender is connected, sand is pneu-
matically conveyed into the blender
vessel,” said Mark Weise, business de-
velopment director of oil and gas ser-
vices for Praxair. “We then add liquid
carbon dioxide to cool down and pres-
surize the vessel and sand in prepara-
tion for pumping.”
After a safety check, completed in
coordination with the service com-
pany and the operator, CO2 begins
pumping down hole at the speci;ed
rate. Praxair’s blender delivers the pre-
set concentrations of sand over the
course of the stage. Once the sand has
been fully pumped, the job is complet-
ed and the system can be disassembled
and moved to the next well pad.
According to Weise, DryFrac has been
used successfully on several jobs. Initial
results have shown up to double the
production over wells in the same formation that were fractured with water.
“These results are generating an interest within the industry and we expect to see more operators using our
technology over the next six to nine
months,” Weise said.
UNDER THE HOOD
Another waterless method of frac-
turing wells relies on low-weight hy-
operators to recycle fluids