American Oil and Gas Reporter - September 2018 - 97

Gas Processing Scenario
A subsequent analysis was undertaken
by EERC to examine CO2 EOR scenarios
employing CO2 captured from natural gas
processing. This analysis modeled the
CO2 vented to the atmosphere during gas
processing and a CO2 EOR scenario analogous to the Bell Creek CO2 EOR project
operated by Denbury. The study incorporated facility-specific data on the raw nat-

ural gas composition entering a processing
facility and the emissions from natural
gas processing, including vented CO2.
In addition, estimates used for associated
CO2 storage incorporated both operational
data from the Bell Creek project and from
numerical simulation models calibrated
to known performance data. As seen in
Figure 3, the analysis compared GHG

emissions for a base-line conventional
system (System 1) against a system with
incremental oil produced through CO2
EOR using CO2 captured from a natural
gas processing facility (System 2).
Results suggest CO2 EOR using CO2
captured from natural gas processing produces both natural gas and oil with an
18-31 percent reduction in CI, compared

FIGURE 3
EERC MJ51957,CDR

System 1

Vented
CO2

Raw Natural Gas
Extraction

Conventional
Oil Extraction

Transport to GasProcessing Facility

Crude Oil
Pipeline
Transport

Separation of
Impurities from
Natural Gas

Petroleum Refinery

Legend
System Boundary

Fuel Transport,
Distribution, and
Point of Sale

Fuel Combustion

Natural Gas

Natural Gas
Transmission,
Distribution, and
Use

System 2

Raw Natural Gas
Extraction

Legend
Upstream Segments
CO2 EOR gate-to-gate
Downstream Segments

Transport to GasProcessing Facility

Separation of
Impurities from
Natural Gas

System Boundary

CO2

Natural Gas

Natural Gas
Transmission,
Distribution, and
Use

Pipeline CO2
Transport

CO2 EOR
Operations
(gate-to-gate)
Crude Oil
Crude Oil
Pipeline
Transport
Crude Oil
Petroleum
Refinery

Fuel

Fuel Transport,
Distribution, and
Point of Sale

Fuel Combustion
Fuel

EERC MJ54476 AI

14
Life Cycle GHG Emissions, Mt CO2eq

CO2 EOR in the North Dakota portion of
the unconventional Bakken petroleum
system ranges from 1.8 billion to 16.0
billion barrels of oil.
Meanwhile, the success of rich-gas injection EOR pilots in the Eagle Ford play
demonstrates that gas-based EOR in unconventional oil formations is both technically and economically viable. Laboratory
studies conducted at the EERC, including
miscibility studies, show that rich gas and
CO2 appear to have similar effectiveness
in mobilizing oil from tight formations.
As industry further develops and refines
strategies to implement gas-based EOR in
unconventional reservoirs and sources of
rich gas become constrained, the concept
of using CO2 as the working fluid for these
projects will be become more attractive.
Broad implementation of CO2 EOR
not only will add to U.S. oil production,
but the associated CO2 storage will reduce
the carbon intensity (CI) of that portfolio.
Reducing CI has been a goal of American
energy policymakers since President
George W. Bush directed DOE to establish
the Regional Carbon Sequestration Partnership Program in 2002.
CCUS can result in reducing the CI of
produced oil because virtually all the injected
CO2 ultimately remains stored in the subsurface rather than being emitted to the atmosphere. The stored CO2 will offset a
portion of the net GHG emissions from the
industrial source of the CO2 and the combustion of the hydrocarbon being produced.
An analysis undertaken by the EERC
and published in peer-reviewed literature
shows that the CI of the oil produced
through CO2 EOR is less than that of conventional oil production. For example, average GHG emissions associated with gasoline and diesel produced from oil generated
by applying EOR using CO2 sourced from
coal-fired power generation are approximately 15 percent less than that of burning
such products derived from crude oil with
national average CO2 emissions characteristics absent offsetting associated storage.
The reduction in GHG emissions is
attributed to the associated storing of
CO2 in the oil reservoir as part of the
EOR process, giving rise to an emission
reduction of approximately 450 kilograms
of CO2 stored per barrel of oil produced.

12
Net Reduction
3.0 MT CO2eq

10

Downstream

8

Gate-to-Gate Crude Oil Extraction
Pipeline Transport of CO2

6

Natural Gas Processing
Natural Gas Extraction

4
2
0
System 1
(Conventional)

System 2
(CO2 EOR)

Greenhouse gas emissions for a base-line conventional natural gas processing system
(System 1) that included conventional oil production and gas processing is compared
with System 2, in which incremental oil is produced using carbon dioxide-enhanced oil
recovery, and the CO2 is captured from the gas processing facility.

SEPTEMBER 2018 97
American Oil and Gas Reporter - September 2018

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