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Research for Deployment: Incorporating Risk, Regulation,and Liability for Carbon Capture and Sequestration

Carbon capture and sequestration (CCS) has the potential to enable deep reductions in global carbon dioxide (CO₂) emissions, however this promise can only be fulfilled with large-scale deployment. For this to happen, CCS must be successfully embedded into a larger legal and regulatory context, and any potential risks must be effectively managed. We developed a list of outstanding research and technical questions driven by the demands of the regulatory and legal systems for the geologic sequestration (GS) component of CCS. We then looked at case studies that bound uncertainty within two of the research themes that emerge. These case studies, on surface leakage from abandoned wells and groundwater quality impacts from metals mobilization, illustrate how research can inform decision makers on issues of policy, regulatory need, and legal considerations. A central challenge is to ensure that the research program supports development of general regulatory and legal frameworks, and also the development of geological, geophysical, geochemical, and modeling methods necessary for effective GS site monitoring and verification (M&V) protocols, as well as mitigation and remediation plans. If large-scale deployment of GS is to occur in a manner that adequately protects human and ecological health and does not discourage private investment, strengthening the scientific underpinnings of regulatory and legal decision-making is crucial.

Potential Groundwater Quality Impacts from Metals Mobilization.

Groundwater merits special attention because it is a precious resource, and it is subject to current regulation. While there are several ways in which large-scale injection or leakage might affect water supplies, most attention has focused on CO₂−brine−rock interactions. While processes in this system could affect both organic and inorganic geochemistry of aquifers, only the mobilization of inorganic compounds, chiefly metals, through dissolution and transport will be considered here.

South Liberty (Frio) Pilot, TX.

In 2004, a DOE pilot field experiment in South Liberty, TX injected 1800 t of CO₂ into the Frio saline formation (29). This injection was designed to validate simulations of CO₂ transport and fate in one of the largest saline formations in the United States. A monitoring well located 100 ft. from the injection well collected direct fluid samples using a U-tube apparatus (30). This tool and others detected arrival of a CO₂ plume in the monitoring well 7 days after injection.

Of note, a substantial amount of dissolved metal was recovered in the U-tube (31). Initially, workers thought that the well casing was reacting to carbonic acid in the reservoir. However, laboratory studies and geochemical analyses confirmed that a substantial fraction of the metals were the product of mineral dissolution, specifically the oxide and hydroxide coatings of mineral grains that represent <2%>31). The rapidity of mobilization and the high concentrations suggested strongly that carbonic acid formed from dissolved CO₂ in formation brines might quickly and dramatically alter groundwater chemistry.

The Frio was the first saline formation analyzed in this way. Ultimately, this result is not unexpected, yet it is not clear whether this effect of metal mobilization is common or significant at depth. It is also not clear what fraction of metals would be transported with CO₂ should it leak to other formations. However, it raised the concern that should CO₂ leak into a shallow freshwater aquifer, there could be consequences that could negatively affect groundwater quality, potentially impacting public health and acceptance of CCS deployment.

Carbonate and Siliclastic Systems.

To a first order, both injection targets and shallow aquifers can be divided into siliciclastic or carbonate systems. This division reflects the primary composition of the reservoir rocks. Carbonate systems chiefly comprise calcite, aragonite, dolomite, and other carbonate minerals that form limestones and dolostones, whereas siliciclastic systems chiefly comprise frag ments of quartz, feldspar, and other siliceous minerals that form sandstones, siltstones, and shales.

This compositional difference greatly affects the response of carbon acid. Silicate minerals react slowly with CO₂, which means that there is little change in porosity and permeability over the duration of injection; however, the brines with dissolved CO₂ will remain acidic. In contrast, carbonate rocks react quickly with CO₂ and could change permeability and porosity quickly; however, the rapid kinetics will result in rapid increase of brine pH and buffering of the brine−CO₂ system, reducing reactivity over time. Because of these competing effects, it is not clear which fundamental rock composition is more prone to leakage or to mobilizations of metals, and little work has focused on direct comparison of these two primary aquifer compositions.

Key U.S. Freshwater Aquifer Settings.

Given the distribution of CO₂ point sources and potential GS reservoirs, it is likely that CO₂ storage will be concentrated in a small number of basins. To understand and appraise the potential for metal mobilization in shallow aquifers, it would be helpful to understand the composition and acid-reaction response near the surface of these basins. Table 2 provides a subset of key shallow aquifers in these basins and some issues around their geology.

Groundwater, Saline Aquifers, and Proposed CCS Project s

Darke County, Ohio is the proposed site of one of the large-scale Carbon Capture and Storage projects. (CCS - aka CO2 Sequestration) Greenville, OH has been selected as the site for the MRCSP's Phase III "Demonstration Project" in which they plan to bury 1 Millon Tons of CO2 in the Supercritical Form known as Supercritical CO2.

This area is a strong agricultural area and it sits on top of a sole source aquifer

Technology has advanced rapidly, whoever thought we'd have this technology in our lifetime?

I question why anyone would want to inject supercritical CO2 into our saline aquifer and destroy the possibility of it being used in the future. What potential mess are we leaving for future generations to clean up?




The quotes below are from the web site - http://www.pnl.gov/gtsp/publications/2008/papers/2008_davidson_impacts_future_demand.pdf

Assessing the impacts of future demand for saline groundwater on commercial deployment of CCS in the United States

Casie L Davidsona*, James J Dooleyb, Robert T Dahowskia
Pacific Northwest National Laboratory, 902 Battelle Avenue, Richland, Washington 99354, USA
Pacific Northwest National Laboratory, 8400 Baltimore Avenue, Ste 201, College Park, MD 20740, USA

This is a very important article - it addresses the potential impact that CCS might have on the future demand for groundwater within the United States especially as these projects increase in number. A number of areas of the U.S. are very dependent upon their groundwater - many are over-utilized or depleted or moving towards depletion as demand grows.

This geological formation in the western Ohio area is known as the Mount Simon Sandstone and it is this same saline aquifer that is considered to be an ideal formation for CO2 waste pumped into the earth as the final deposit for CO2 sequestration projects. It is deposited in the geological formation forever, not stored to be retrieved at a later date.

Water is our most precious resource.

The bold areas in red are excerpts from the article referenced below. They have been enhanced in red for those who skim articles. The excerpts are from random paragraphs and may or may not be in order... please read the entire article.

Please be sure to read the entire article http://www.pnl.gov/gtsp/publications/2008/papers/2008_davidson_impacts_future_demand.pdf

"The need to meet future water demands may lead some parts of the nation to consider supplementing existing supplies with lower quality groundwater resources, including brackish waters that are currently not considered sources of drinking water but which could provide supplemental water via desalination. In some areas, these same deep saline-filled geologic formations also represent possible candidate carbon dioxide (CO2) storage reservoirs. The analysis presented here suggests that future constraints on CCS deployment – due to potential needs to supplement conventional water supplies by desalinating deeper and more brackish waters – are likely to be necessary only in limited regions across the country, particularly in areas that are already experiencing water stress."

(Please see map of Ohio on the above web site)

"As Figure 1 illustrates, some areas of the U.S. use very little groundwater to supply their populations with drinking water. In particular, Appalachia, the Northeast and certain areas in the Midwest and Pacific Northwest rely predominantly on surface waters to meet their public supply needs. In other areas, however – particularly the Southwest, Gulf Coast and Florida, and certain other parts of the Midwest – groundwater provides a large fraction of the total public water supply, well over 50 percent in many areas. It is also worth noting that the use of groundwater to supply public drinking water appears to be on the rise. In 1985, 379 counties in the U.S. supplied more than 80 percent of their population with groundwater; in 1995 there were 436, a 15 percent increase [9]."

"3.5. Ohio River Valley Aquifers
Because the most promising CO2 storage resource in the Ohio River Valley does not underlie a major drinking water aquifer system in many areas of interest for CO2 storage, there are unlikely to be significant conflicts regarding saline water use for CCS. However, the Mt. Simon Formation, one of the key CO2 storage targets in this region, shallows to the northwest, in northern Illinois, where formation waters are fresh and the aquifer is an important groundwater source."

(Note- Greenville, Ohio sits on a freshwater sole source aquifer)

"Adapting to growing populations, declining water levels within key aquifers, and changing precipitation patterns may further strain heavily used groundwater resources in areas already impacted by water supply issues. Within certain regions of the nation, water scarcity concerns may prompt further consideration for targeting nearby high salinity or brackish water in deep aquifers for treatment by desalination technologies to augment more conventional supplies. Deep geologic formations that could be used as a permanent repository for anthropogenic CO2 in climate change mitigation efforts via CCS contain highly brackish waters that in select regions might represent potential targets for future waters supplies (particularly if they are below the salinity of seawater, approximately 35,000 mg/L TDS). This possibility might present a competing use for these deep geologic formations, and should be examined to estimate the potential probability, location, and magnitude, of such impacts."

"The likelihood that deep, saline groundwaters exceeding the USDW salinity threshold may be demanded as future sources of drinking or irrigation water increases in areas where groundwater currently supplies a significant portion of the region’s water supply; in areas with already constrained water supplies, such as the High Plains / Ogallala region; in areas where significant population growth is expected to overburden current surface and groundwater resources within the near- to mid-term, such as in parts of the Southwestern U.S. and areas of Texas; and in areas where there are limited other sources of saline waters (i.e., seawater) nearby."

' In areas that meet one or more of these criteria and also have a significant potential demand for deep geologic CO2 storage, there exists the possibility for differences of opinion regarding the best use of the saline groundwater underlying these regions. In such cases, permitting or garnering public acceptance for proposed CCS projects will require regulators and potential CCS operators to strike a balance between the future needs for high quality drinking and agricultural water, and the use of CCS in a given area as a climate change mitigation strategy."