American Oil and Gas Reporter - April 2017 - 122

ConventionCoverage: Illinois Oil & Gas Association

Residual oil zones in the Cypress Sandstone may boost the Illinois Basin's oil
production by using nonconventional
carbon dioxide enhanced oil recovery,
says Nathan Webb, an assistant petroleum geologist with the Illinois State
Geological Survey.

Revelant is experimenting with operators
shutting in ENERCAT-equipped wells on
a regular basis, such as three out of seven
days. He said the tool allowed for startup
without any stimulation, and the wells
produced significantly more during their
run times. Before production begins to
flag, the operator shuts in the well again,
and the cycle repeats.
In one trial, a stripper well operator
saw his production increase 60 percent
after a cycle of three shut in days and
four days of production, suggesting that
the ENERCAT had both a mitigative and
preventative effect on the reservoir, as
well as the perforations, Edwards said,
and the operator also saw his electricity
and monitoring costs decrease.
Cypress Sandstone
The residual oil zones contained in the
Illinois Basin's Cypress Sandstone hold
the potential for significant oil production,
assessed Nathan Webb, an assistant petroleum geologist with the Illinois State Geological Survey. He told IOGA the U.S. Department of Energy is studying the formation
because of its potential for nonconventional
carbon dioxide enhanced oil recovery.
The Cypress typically has a thin pay
zone at the top of the sandstones, with
residual mobile oil above a thick column
of brine saturation, he explained.
"These things typically are difficult

to produce economically, because you
have a lot of issues with water coning
and water management," Webb said. "We
are in the process of looking at these
from a nonconventional EOR standpoint,
possibly producing more of this oil from
the main pay zone at the top but also
looking at the potential for residual oil
that may lie below this main pay zone."
These ROZs had the same characteristics as the swept portions of a mature
waterflooded area, he said, adding the
Permian Basin has some of the classic
examples of these zones, boasting 15-35
percent oil saturation. Typical recovery
rates with carbon dioxide EOR are 1020 percent, he estimated.
The formation being studied is a multistory sandstone body, in which permeability is highest in the lower part of
each channel, Webb said. Water coning
is evident in the top of the play, while the
surrounding areas show insufficient production. In a computer simulation run by
ISGS, he described the CO2 pathway.
"After injecting, the CO2 is preferentially moving out into these higher permeability zones, as opposed to the low
permeability zones at the top of the reservoir. The oil saturation profile shows the
buoyancy and solubility of the CO2 is
sweeping oil-not only from the ROZ but
it also is cleaning the main pay zone at
the top. After eight years of EOR in the
simulator, a lot of the main pay zone is
cleaned up and we are continually reducing
the saturation within the residual oil
zone," he said.

The survey is seeking physical validation, and plans to drill a core through
the entire Cypress Sandstone to physically
test whether there is oil saturation below
the main pay zone, Webb said.
"Reservoir simulations are showing
potential for increased oil production
from the main pay zones and new production from these ROZs," he indicated.
"Our goals are to get a handle on whether
these ROZs exist, propagate our methods
out to the region, and assess what is the
regional resource of ROZs within the
Cypress. We have to better understand
how to develop the Cypress Sandstone
deposits, both from the main pay zone
perspective and the ROZ."
Hannas Leetaru, senior petroleum geologist and head of the ISGS petroleum
geology group, reported on proposed carbon sequestration projects in Illinois-one
near Decatur, and the other to the east, in
Champaign County. "The projects will
look for places where we could sequester
CO2. The data we get will include highresolution wireline logs, core samples,
and a lot of things that will benefit the
oil and gas industry in understanding potential reservoirs," he detailed.
One ancillary benefit will be regional
maps with more detailed information on
geology and rock characteristics that will
provide useful data for exploration projects,
he said. ISGS also is leading Siluro-Devonian exploration in Sangamon Arch
near Mount Auburn, Leetaru said, adding
the formation holds potential for a new
play.
❒

Producers May Have To Settle
For Stable, Not High, Oil Prices
EVANSVILLE, IN.-While many media reports indicate oil prices have nowhere
to go but up, producers may have to be
happy with stable prices, Arthur Berman
told the Illinois Oil & Gas Association's
annual convention and trade show.
Berman, a geological consultant who
works for exploration and production
companies and capital groups, predicted
that despite production cuts from members
of the Organization of Petroleum Exporting
Countries, oil prices were likely to remain
in the $45-$50 a barrel range. He also
warned an uncertain future for Bakken
Shale production could impact U.S. supplies and prices.

122 THE AMERICAN OIL & GAS REPORTER

"Today, 2016 prices are-more than
anything else-a function of sentiment,"
Berman asserted. "There really has not
been any kind of change in fundamentals
that has lifted prices from $26 to an
average of $43, only an awful lot of expectations that the OPEC cut will make a
big difference. We are likely to set ourselves up for disappointment, but I think
that OPEC cut was more about putting a
floor under prices than trying to raise
them."
One of the reasons the cartel reduced
members' oil output was a lack of spare
production, he said. By July, spare capacity was less than 1 million barrels a

American Oil and Gas Reporter - April 2017

Table of Contents for the Digital Edition of American Oil and Gas Reporter - April 2017