Carbon Dioxide Enhanced Oil Recovery: USGS National Assessment of Oil and CO2 Retention

In 2020 the U.S. Geological Survey (USGS) completed a probabilistic assessment of how much technically recoverable oil could be produced by applying current carbon dioxide enhanced oil recovery (CO2-EOR) technology to suitable conventional oil reservoirs beneath the onshore and State waters areas of the conterminous United States. It also estimated the mass of CO2 that would stay stored (retained) in those reservoirs once the process was complete.

The team evaluated more than 3,500 oil reservoirs that were miscible with injected CO2, in 185 previously defined USGS plays within 33 petroleum provinces of 7 national regions.

The totals

P5, P50 and P95 are probability percentiles: the 5-, 50- and 95-percent probabilities that the true resource is less than or equal to the value shown. This follows standard statistical practice, where a percentile is the value below which a given share of observations falls, and differs from the terms the petroleum industry uses. The percentiles were aggregated with a method that allows for partial dependencies between assessment units, so they do not add up to the totals. Values are given to two significant figures.

Where the potential is

The West Texas and Eastern New Mexico region — mainly its Permian Basin — and the Gulf Coast region together hold 60 percent of the mean assessed oil potential and 61 percent of the mean assessed CO2 retention. The Midcontinent region and the Rocky Mountains and Northern Great Plains region also have significant potential.

Alaska (Region 1), Hawaii and federally owned offshore areas were not assessed.

Figure 1. Regional mean estimates of (A) technically recoverable oil that could be produced with CO2-EOR and (B) the mass of CO2 that could be retained, in miscible oil reservoirs beneath onshore and State waters areas of the conterminous United States. Regional means are given to two significant figures and sum to the totals. Credit: U.S. Geological Survey.

Figure 2A. Estimated oil, in millions of barrels, that could be produced with CO2-EOR, by region: bars show the P5, P50 and P95 estimates and a dashed line the mean. Region and province boundaries are from the USGS 1995 National Oil and Gas Assessment. Credit: U.S. Geological Survey.

Figure 2B. Estimated mass of CO2, in millions of metric tons, that could be retained with CO2-EOR, by region. Credit: U.S. Geological Survey.

Why the USGS made this assessment

The Energy Independence and Security Act of 2007 authorised the USGS to carry out a national assessment of geologic storage resources for CO2, and asked it to estimate the "potential volumes of oil and gas recoverable by injection and sequestration of industrial carbon dioxide in potential sequestration formations" (42 U.S.C. 17271(b)(4)). For that, the USGS:

• built a national database of the geologic and engineering parameters needed to screen oil reservoirs for CO2-EOR (Carolus and others, 2017);
• published a probabilistic method for assessing qualifying reservoirs' technically recoverable hydrocarbons and the CO2 left in them after CO2-EOR (Warwick and others, 2019).

Applying CO2-EOR to known hydrocarbon reservoirs can add to the nation's recoverable resources. Because some of the injected CO2 stays in the reservoir, using CO2 from human activity in the process could help reduce the amount released to the atmosphere, where it can contribute to global warming as a greenhouse gas. The International Energy Agency (2015) estimated that oil produced with human-made CO2 in CO2-EOR carries on average about 63 percent less carbon emitted than oil produced by traditional methods.

What the estimates do and do not include

The method follows current industry practice, which aims to maximise oil production rather than CO2 retention: in the general absence of regulations or economic incentives, industry keeps the CO2 left underground to a minimum. The results are therefore estimates of the technically recoverable oil available with CO2-EOR.

They leave out economic, logistical, legal, environmental and political constraints, such as:

• whether pipelines are available to supply CO2;
• surface ownership or use;
• tax incentives for recovering the resource.

Results by province

Table 2 gives the estimates for each province, grouped by region. The P50 (median) can be lower than the mean because most of the output distributions are skewed to the right; entries are to two significant figures, and means may not add to the totals because of rounding.

Table 2. Estimated oil that could be produced with CO2-EOR (millions of barrels) and CO2 that could be retained (millions of metric tons), by region and province; a four-digit code identifies each USGS province. Credit: U.S. Geological Survey.

Sources

• Warwick, P.D., Attanasi, E.D., Blondes, M.S., Brennan, S.T., Buursink, M.L., Cahan, S.M., Doolan, C.A., Freeman, P.A., Karacan, C.Ö., Lohr, C.D., Merrill, M.D., Olea, R.A., Shelton, J.L., Slucher, E.R., and Varela, B.A., 2022, National assessment of carbon dioxide enhanced oil recovery and associated carbon dioxide retention resources — Summary: U.S. Geological Survey Fact Sheet 2021–3057. https://doi.org/10.3133/fs20213057
• Fuller results: the companion data release and USGS Circular 1489 (Warwick and others, 2022).
• The figures, tables and the explanation of the percentiles are taken from the fact sheet's PDF; the imported text had lost them.
• Rewritten in hubnx's own words.