ACHIEVING “NO NET CARBON” EMISSIONS ASSOCIATED WITH CO2
CAPTURED FOR USE IN CO2 ENHANCED OIL RECOVERY
Michael L. Godec,1 George Koperna1
1
Advanced Resources International, Incorporated
Abstract
A number of commenters on EPA's “Clean Power Plan” and other proposals to encourage carbon
capture and storage (CCS) via CO2 injection for enhanced oil recovery (EOR) criticize such
proposals because they fail to consider the greenhouse gas (GHG) emissions associated with
production, refining, and combustion of additional oil reserves made available through CO2-EOR.
Some object to the use of CCS as a mechanism to extract more fossil fuels from the earth that will,
for the most part, be burned for energy and themselves contribute GHGs to the atmosphere.
The approaches used in, and the corresponding results from, studies of the life cycle emissions of
CCS and/or CO2-EOR that provide the basis of this commentary vary considerably, and are utilized
selectively. This paper will provide a critical review of these studies, and show how they should be
appropriately interpreted. For the most part, the differences primarily relate to what components are
considered as part of the emissions life cycle analysis.
For example, many studies conclude that the net life cycle of GHG emissions for just CO2-EOR
projects are larger than the CO2 injected and stored in association with CO2-EOR. These consider
only the CO2-EOR project itself, not the CO2 captured that might otherwise be emitted, but do
generally consider the CO2 emissions associated with the oil produced, when consumed. In contrast,
when the entire capture, transport, and CO2-EOR injection is considered, others conclude that CO2EOR projects using CO2 captured from power plants can store significant amounts of net CO2, thus
reducing the GHG emissions impacts of power generation and oil production. However, these
studies have, for the most part, used boundaries that exclude emissions associated with the
combustion of processed products manufactured from the produced crude oil.
Also very important in these studies are the assumptions for CO2 utilization – the amount of CO2
needed to recover the incremental oil from CO2-EOR – which then provides the basis for the
amount of CO2 assumed to be stored during CO2-EOR; the quantity against which offsetting CO2
emissions are compared. One study concluded that this was the most important parameter that can
impact estimates of net emissions from CO2-EOR operations.
Most such analyses use assumptions of CO2 utilization for CO2-EOR that are based on historical
CO2-EOR operations. CO2-EOR projects were traditionally designed to minimize the amount of
CO2 injected per incremental barrel of oil produced. Since the purchased cost of CO2 is generally
the largest cost component of a CO2-EOR project, operators attempt to optimize incremental oil
production in CO2-EOR projects by minimizing the amount of CO2 injected per barrel produced.
Therefore, assessments of CO2 storage potential associated with CO2-EOR based on historical ratios
of CO2 injected to incremental oil produced probably do not accurately characterize future potential.
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In a future governed by controls on GHG emissions, or by a market that places a value on CO2
emissions reduction, the traditional concern about the high cost of CO2 is replaced by the objective
of taking full advantage of the potential value associated with stored CO2. This likely will result in
the use of greater volumes of CO2 for CO2-EOR.
Moreover, new technologies and operating practices are also resulting in increased volumes of CO2
injected per incremental barrel of oil recovered. As will be described in detail in this paper, based
on these historical utilization values, most studies currently assume values for CO2 utilization on the
order of 0.2 metric tons of CO2 per incremental barrel of oil recovered. In contrast, current EOR
operations in the Permian Basin are approaching utilization values of 0.4 metric tons of CO2 per
barrel of oil, thus making them twice as efficient at storing CO2. Alternative assumptions about CO2
utilization can result in additional increases in the volumes of CO2 stored per barrel of oil recovery,
and thus result in a further improvement in net CO2 emission reductions associated with CO2-EOR.
Using numerical modeling applied to several specific CO2-EOR project case studies, this paper will
examine a number of different CO2-EOR development options that could greatly increase the
amount of CO2 injected, and ultimately stored, to recover incremental oil via the application of
CO2-EOR. The objective would be to speculate on the operational, technological, and economic
drivers that may need to be overcome to achieve “zero net carbon emissions” associated with CO2EOR, even when the emissions from the combustion of oil are considered.
Moreover, the paper will begin to speculate how even greater storage efficiencies with CO2-EOR
can be realized. For example, basins with significant potential for CO2-EOR also often possess
large capacity for non-EOR storage. Substantial opportunities exist for co-locating CO2-EOR and
CO2 storage operations in deep saline formations utilizing the same CO2 injection wells and surface
infrastructure used for CO2-EOR. Moreover, additional storage capacity should exist in reservoirs
targeted for CO2-EOR after CO2-EOR operations are complete.
Finally, this paper will explore alternative perspectives on the net carbon emissions associated with
CO2-EOR. For example, if one thinks of CO2-EOR’s oil as additive—additional oil that would
otherwise not be consumed—and does not take into account the displacement of more carbonintensive electric power by CCS, then CO2-EOR could release more CO2 than it stores. However, if
one believes that oil produced by CO2-EOR will mostly displace other sources of oil to meet this
demand, non-CO2-EOR oil production processes produce twice (or more) the GHG emissions as
CO2-EOR projects.
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