MUST READ - Educate yourself about the risks involved with CO2 Sequestration

I consider this a must read document -

http://www.epa.gov/climatechange/emissions/downloads/VEF-Technical_Document_072408.pdf

Evaluating Geological CO2 Sequestion Sites (Permanent Storage)

"This report describes a screening and ranking framework (SRF) developed to evaluate
potential geologic carbon dioxide (CO2) storage sites on the basis of health, safety, and environmental (HSE) risk arising from possible CO2 leakage. The approach assumes that HSE risk due to CO2 leakage is dependent on three basic characteristics of a geologic CO2 storage site: (1) the potential for primary containment by the target formation, (2) the potential for secondary containment if the primary formation leaks, and (3) the potential for attenuation and dispersion of leaking CO2 if the primary formation leaks and secondary containment fails. The framework is implemented in a spreadsheet in which users enter numerical scores representing expert opinions or general information available from published materials, along with estimates of uncertainty to evaluate the three basic characteristics in order to screen and rank candidate sites. Application of the framework to the Rio Visa Gas Field, Ventura Oil Field, and Mammoth Mountain demonstrates the approach."

The full report can be accessed here

Read the full article here

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.

Danger - CCS Injection and Leakage

The article, from which these quotes were taken, can be found on the link below (words enhanced to help readers who skim articles)
http://mydocs.epri.com/docs/CorporateDocuments/EPRI_Journal/2007-Spring/1014795_CO2Storage.pdf

While the concept of geologic storage seems simple enough, a CO2 injection well is a surprisingly complicated system. Multiple cement casings and provisions for monitoring are required to ensure that the supercritical fluid reaches only appropriate storage formations and stays there. In particular, steps must be taken to keep the CO2 from interfering with sources of drinking water at shallower depths. In the injection zone itself, special cement must be used to prevent damage to the casing from acids that form when CO2 reacts with the in situ saline solution.

A variety of measurement, monitoring, and verification (MMV) technologies will also need to be incorporated into a complete storage system to make sure the CO2is not leaking into the surrounding environment. Some off-the-shelf technologies,such as seismic imaging of subterranean formations, are already being used to trackthe underground migration of injected CO2, and sampling of groundwater couldprove useful for detecting leakage directly. Detecting small rates of leakage over long periods of time, however, will require higher-resolution measurements and the development of highly precise baseline data. More-sensitive MMV techniques thatcan measure the actual amount of CO2 in storage may also be needed for purposes of greenhouse gas mitigation reporting.

The issue of leakage is critical from both global and local perspectives. Even gradual leakage from numerous sites may provide enough CO2 reentering the atmosphere to undermine efforts to stabilize greenhouse gas concentrations. Locally, leakage from an underground storage site could present an immediate hazard to humans and ecosystems.

The most dramatic type of CO2 release would come from a blow-out at an injection well, which could produce high enough concentrations (7–10%) of the gas in the vicinity to endanger human life.

Undetected leakage from a faulty well or through ground fractures would probably be more diffuse and primarily affect groundwater and surface ecosystems. In particular, aquifers used as a source of drinking water could be harmed, either by acidification resulting from direct contact with large amounts of CO2 or by the seepage of brines displaced by CO2 during the injection process.

Because CO2 is heavier than air, it also could accumulate in lowlying geographic areas or in basements and potentially threaten human health.
Research is currently under way to improve CO2 leak detection and develop possible
remedial measures. Specifically, MMV technologies are needed that would detect
potential leaks long before they pose any danger to water supplies or surface ecosystems.

Seismic imaging, for example, can reveal deep subsurface faulting and abandoned
wells that might permit leakage by providing a route to the surface, and this
type of examination is expected to become a routine part of storage site evaluation. In addition, some experiments are under way to begin to investigate leakage rates for different types of storage and under a variety of injection conditions.

Several kinds of remediation techniques also need to be explored, including the extraction and purification of contaminated groundwater, the interception and reinjection of leaking CO2, and the removal of stored CO2 for injection elsewhere.

“The available monitoring methods are promising, but more experience is needed to establish detection levels and resolution."

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