American Oil and Gas Reporter - September 2018 - 96

SpecialReport: Reservoir Modeling & EUR
Size Of The Prize
EIA's 2018 Annual Energy Outlook
forecasts U.S. production from CO2 EOR
will grow to 390,000 bbl/d by 2025. Literature suggests the potential for CO2
EOR from conventional oil fields in the
United States is substantially larger than
that projected by EIA.
A U.S. Department of Energy-funded
study by Kuuskra and others (2013) concluded that, assuming an oil price of $85
a barrel and a CO2 price of $40 a tonne,
applying "next generation" CO2 EOR
technology could yield 100 billion barrels
of economically recoverable oil. That
study also estimates the volume of CO2
required to recover 100 billion barrels of
oil is 30 billion tonnes, which is equal to
35 years of CO2 emissions from 140 gigawatts of coal-fired power.
To date, commercial CO2 EOR has
been applied almost exclusively to conventional oil reservoirs. Unconventional
reservoirs, including tight oil systems
such as the Bakken in North Dakota or
residual oil zones, offer considerable increased potential to use CO2 for enhanced
oil recovery, subject to developing the
appropriate advancements in technology.
Studies conducted by the EERC, including field trials, have shown initial
promise and underline the potential of
these future EOR applications. EERC results suggest the size of the prize for

CO2 EOR projects.
A study conducted by the Energy &
Environmental Research Center (EERC)
at the University of North Dakota examined CO2 utilization rates at 31 CO2
EOR projects. The results show that
CO2 utilization rates tend to be greatest
near the beginning of the flood as the
reservoir begins to fill with CO2. As
CO2 EOR projects mature, the proportion of CO2 recycled increases and CO2
utilization rates begin to decline, typically reaching a ratio of between 4.8
and 10.5 Mcf per barrel of incremental
oil produced.
Utilization rates for the Bell Creek
Field, which is being developed in a
staged approach (i.e., new geographic
development phases are being brought
on line periodically), are trending in line
with typical early-stage performance observed for the EOR fields in the study.
As the Bell Creek project matures and
the potential to develop additional phases
is exhausted, utilization rates will begin
to decline, resulting in a reduced rate of
associated storage. This could result in
an increased CO2 supply that could be
diverted to a new EOR prospect.
In total, CO2 EOR at the Bell Creek
Field is expected to result in 40 million50 million barrels of incremental oil and
is forecasted to result in upward of 15
million tonnes of associated CO2 storage.

lization and storage (CCUS).
The CO2 storage inherent in EOR also
is referred to as "associated storage." Associated storage is considered by many
environmental and energy policymakers
to be a technically and economically
viable means by which greenhouse gas
emissions can be reduced.
An EOR project at the Denbury-operated Bell Creek oil field in southeastern
Montana provides an example of how
applying anthropogenic CO2 can result
in incremental oil recovery and associated
CO2 storage. The anthropogenic CO2 for
the field is sourced from the Lost Cabin
and Shute Creek natural gas processing
facilities in Wyoming, and is transported
to the Bell Creek oil field by pipeline.
Between the beginning of CO2 injection
in May 2013 and December 2017, more
than 4.8 million barrels of incremental
oil have been produced from the field,
resulting in more than 4.8 million metric
tons (tonnes) of associated CO2 storage
(Figure 2).
CO2 Utilization
Metrics used by reservoir engineers
to determine the efficiency of CO2 EOR
include CO2 utilization factors, CO2 retention and incremental oil recovery.
These factors may be important parameters
in assessing associated storage potential
that may be realized by existing or new
FIGURE 2

80,000
70,000

Total Gas Purchased

5.000

Net CO2 Stored*

4.500
4.000

Source: Denbury (January 2018)
*CO2 volumes corrected for gas composition.

3.500

60,000

3.000

50,000

2.500

40,000

2.000

30,000

1.500

20,000

1.000

10,000

0.500

0.000

Monthly Oil Production (bbl)

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M -14
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M -14
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M -15
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M -1
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Ju -15
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No -15
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Ja -15
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M -16
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M -16
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No -16
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Ja -16
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M -17
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Cumulative Associated CO2 Storage (MMcf)

90,000

Cumulative Associated CO2 Storage (Million Tonness)

100,000

140,000
120,000

Phase 1

Source: Montana Board of Oil & Gas
Conservation (December 2017)

Phase 2

Phase 3

Phase 4

Phase 5

100,000
80,000

Phase 1 CO2
Injection Start

60,000

Water Flood

40,000
20,000
0
1986

1990

1994

1998

2002

2006

2010

2014

2018
EERC KL55163.AI

Cumulative oil production and associated carbon dioxide storage are shown since the start of CO2 EOR at the Bell Creek oil ﬁeld.

96 THE AMERICAN OIL & GAS REPORTER

American Oil and Gas Reporter - September 2018

Table of Contents for the Digital Edition of American Oil and Gas Reporter - September 2018