Modeling exercises indicate carbon dioxide enhanced oil recovery might recover a considerable amount of technically and economically incremental oil in different regions of the US under various technology scenarios.
The US Department of Energy's National Energy Technology Laboratory and Advanced Resources International carried out this assessment that found state-of-the-art best practices have a potential for recovering more than 47 billion bbl of oil and application of next generation technologies could recover in excess of an additional 30 billion bbl.
CO2 EOR
Enhanced oil recovery using injected carbon dioxide for miscible displacement of residual oil currently recovers about 250,000 b/d of incremental oil in the US. About 70% of this oil is produced in the Permian basin of West Texas and Eastern New Mexico, where for the past several decades the driver for CO2 flooding has been the serendipitous combination of a relatively low-cost natural CO2 source and reservoirs that are well suited in terms of both geology and fluid properties for CO2 flooding.
More recently, the number of CO2-EOR applications has increased in other areas where the same situation occurs, such as Mississippi-Louisiana and Wyoming-Colorado. In all cases, a core group of projects provides the economic motivation for an initial pipeline, and the network of CO2 distribution infrastructure grows as companies develop additional projects.
With the potential for large amounts of anthropogenic CO2 being captured and made reliably available at relatively low cost as a result of possible climate-change regulations, there is a possibility of a similar scenario occurring in other US regions that have depleted oil reservoirs amenable to CO2 EOR but not a ready, low-cost CO2 source.
NETL and ARI employed a proprietary reservoir database to identify reservoirs in large oil fields where CO2 EOR could produce large amounts of incremental oil. This analysis also quantified the volume of CO2 that would remain sequestered in these reservoirs, a result yielding a rough measure of the dual benefits that a CO2 storage-EOR paradigm could make possible.
Some of these reservoirs could become anchor fields for new CO2 collection and distribution infrastructure with anthropogenic CO2. This could lead to an increase in oil production in some mature basins and an associated increase in related economic benefits.
The same infrastructure also could transport CO2 for sequestration in deep saline formations, depleted gas fields, or other storage locations.
Regional clusters
A prior study by the team assessed the role that best practices CO2-EOR technologies could play in US oil recovery. It noted that CO2 EOR could produce an additional 85 billion bbl of oil from the 400 billion bbl remaining unproduced in reservoirs across 11 US basins. The additional recovery would require:
• Introducing best practices technology to regions where it is currently not yet applied.
• Lowering risks by conducting research, pilot tests, and field demonstrations in geologically challenging fields.
• Providing state production tax incentives, federal investment tax credits, and royalty relief.
• Establishing low-cost reliable CO2 supplies.
In the current effort, NETL and ARI used the same proprietary database of large oil field data for identifying clusters of fields where CO2 EOR could be viable and economical, and collectively, sufficiently large to serve as focal points for the development of new centers of CO2-EOR production.
This study assessed more than 2,000 reservoirs and selected a subset of reservoirs, each individually containing more than 10 million bbl of original oil in place and located in fields with more than 50 million bbl of OOIP.
Of this subset, the assessment only evaluated reservoirs deeper than 3,000 ft and with oil gravity greater than 17.5° because these are the reservoir conditions for which CO2 could become miscible with the in-place oil, facilitating enhanced recovery.
Based on the application of state-of-the-art best practices for CO2 EOR, this analysis indicates that the US reservoirs potentially could produce more than 47 billion bbl of technically recoverable oil. While the analysis shows that the Permian basin accounts for a large portion of this recoverable oil, there are billions of barrels of potential in California, the Gulf Coast, the Mid-Continent, and Rocky Mountain states as well (figure and Table 1).
Much of this oil could become producible with the availability of reliable sources of reasonably priced CO2 and the completion of precommercial operations performance analyses.
Of particular note is that 6 of the 11 basins assessed currently do not have commercial CO2-EOR projects. Together these regions contain more than 20 billion bbl of technically recoverable oil—a major resource.
Moreover, several regions have scores of gigawatt-scale electric power generation facilities that emit large amounts of CO2. The overlay of CO2-EOR amenable oil reservoirs and power-generating plants presents a opportunity to expand conventional CO2-EOR operations to noncore areas while simultaneously sequestering large quantities of CO2.
Next-generation technology
The team also analyzed the impact of applying next generation CO2-EOR technologies that go beyond the current state-of-the-art. These technologies include:
• Increasing injected CO2 to 1.5 hydrocarbon pore volume, considerably beyond what operators traditionally have used.
• Implementing innovative flood design and well placement options for contacting and producing less efficiently waterflood swept portions of the reservoir, for example, adding new horizontal and vertical wells and using gravity-stable designs in steeply dipping reservoirs.
• Increasing injected water and CO2 viscosity in water-alternating-gas floods
• Adding miscibility enhancers for lowering the pressure required for full miscibility.
The team modeled these alternatives on a reservoir-by-reservoir basis using a customized version of the stream-tube model CO2-PROPHET, originally developed by NETL.
The results (Table 2) show that the technically recoverable oil with the application of next generation technologies is in excess of 30 billion bbl of incremental oil yielding a total recoverable resource of 77.6 billion bbl when added to the 47 billion bbl recovery with state-of-the-art best practices.
New CO2-EOR centers
A large portion of the 77.6 billion bbl, nearly a third, is in the Permian basin. But even in the birthplace of CO2 EOR, nearly half of the estimated technically recoverable resource will depend on new technologies.
Although a few companies already have begun to apply these practices in the Permian basin, most have not. More interestingly, if companies can implement these new technologies hand-in-hand with new sources of CO2, areas such as California, the Midcontinent, the Northern Plains, and Appalachia could become new CO2-EOR hot spots.
Looking closely at just Southern California and the Midcontinent, we see that both areas could produce large amounts of incremental oil if a way can be found to capture, collect, and transport CO2 (Table 3).
Southern California could economically (at $70/bbl oil price and $45/tonne CO2 price) produce 8.6 billion bbl of oil and simultaneously store 1.9 billion tons of CO2 with the development and application of next-generation technologies.
The Midcontinent under the same circumstances could produce and store about the same volumes. The total volume of CO2 that reservoirs could store within all of the regions under a next generation technology scenario is 18 billion tons.
It is also important to remember that estimates contained in Table 2 are based on an analysis of the largest reservoirs in the largest fields. Once a CO2 delivery infrastructure is developed around anchor projects, smaller reservoirs in smaller fields may also become economic targets for CO2 EOR.
A related analysis (unpublished) evaluated the potential for applying CO2 EOR to residual oil zones beneath the original oil-water contact in large reservoirs. In some areas, large volumes of incremental oil could be produced and equally large volumes of CO2 could be stored in these previously untapped segments of the nation's large oil reservoirs.
An estimate is that these deep, water saturated sections of mature fields could store more than 54 billion tons of CO2.
Energy security, environmental goals
This analysis highlights the need for a series of conventional CO2-EOR pilot tests in noncore areas and enhanced research focused on next generation CO2-EOR technologies, both of which will help catalyze a nationwide CO2 EOR and carbon storage industry.
These R&D activities must be coordinated to advance the energy security, environmental preservation, and economic goals of our nation by reducing oil imports on a barrel-for-barrel basis, capturing and injecting CO2 underground, and creating well-paying jobs in rural areas.
CO2 EOR can provide an economic incentive that reduces the risk of carbon capture and storage and could help jump start development of infrastructure that will ultimately enable large portions of the nation's CO2 emissions to be sequestered in more geologic storehouses.
The authors
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