**3. Risk assessments**

250 Fossil Fuel and the Environment

A pilot ECBM project financed by the US DOE was developed in the San Juan Basin in New México, with the use of 4 CO2 injection wells and 16 methane production wells, besides an observation well. The methane production started in July 1989 and the CO2 injection began in April 1995 and continued until August 2001, when the operations were suspended to study the results. Figure 13 shows the results of the variations in methane output as a result

Fig. 13. Evolution of Production/Injection of the UCBM Pilot Project of Alison

Storage and monitoring are considered to be single step, because monitoring is required to assure that the CO2 stored will not leak out to the atmosphere. According to the report of the Special Intergovernmental Panel on Climate Change (IPCC, 2005), this monitoring aims to verify possible leaks or other aspects indicating deterioration of the storage over the long term, to assure there are no risks to the environment. Various technologies can be used to

Monitoring by a network of sensors placed at points distant from the injection sites.

indicates mitigation routes in case of leaks or malfunctions of the system.

All the data gathered by these monitoring efforts are fed into computer systems equipped with "intelligent" software as part of a risk management system, which besides indicating tendencies that can foretell risky situations and determine operational changes, also

of the injection of CO2 (Reeves & Clarkson, 2003).

Source: US DOE.

**2.6 Storage and monitoring** 

perform different types of monitoring:

 Monitoring of the injection flow and pressure; Monitoring of the underground CO2 distribution; Monitoring of the integrity of the injection wells; Monitoring of the local environmental effects; and Risk is the product of the probability of a negative event's occurrence and the magnitude of the consequences. Risk management is a tool used to make decisions to help manage adverse events. For proper assessment of risks, it is necessary to identify all the possible causes of risk and their consequences. This can be done by preparing a chart showing the series of risk-posing events that can lead to a catastrophe, as shown in Figure 14.

Fig. 14. Series of Risks

Normally in industrial undertakings, the causes of events with large adverse effects are treated by managing the technology, that is, by specifying the equipment and materials, preparing rules and procedures, training programs, etc. The effort to reduce risk is concentrated in diminishing the probability of the occurrence of the causes that can trigger a series of events that lead to catastrophe and to assess the consequences. These consequences are analyzed by using the data on the area surrounding the project, its population and natural resources. Therefore, contingency plans are drawn up for mitigation of the catastrophic events if they occur. However, the focus is on the causes.

The risks of CCS projects are hybrid in nature, meaning they are a combination of technological and natural risks, because the possibility of leaks and other problems does not depend on the technology alone. The size of the reservoir, demographic changes, seismic behavior of the region, micro-climate and many other factors can modify the characteristics of the process and thus its complexity. Hence, there is less control over the causes that can lead to a catastrophic event, and it is important to monitor and identify anomalies in the process that can require taking action to control the emergency, by application of contingency plans prepared in advance.

The magnitude and complexity of the events involved in CCS projects prevent the application of traditional risk management based on administrative procedures and operational controls. Unlike an industrial plant, the CCS process is part of a natural formation that is responsible for its final function. The activities of the people in the surrounding area and the possibility of seismic events that trigger natural geophysical and geochemical changes in the reservoir are just some of the aspects that must be considered to

Carbon Capture and Storage – Technologies and Risk Management 253

low acceptance, offshore projects require a much greater investment in constructing the

Failures of carbon pipelines can be caused by holes or complete ruptures. In both cases the

The climatic and geological aspects of the area where a carbon pipeline is or will be installed directly influence the effects suffered by the materials used in their construction. Besides this, these aspects also influence the choice between a buried or aboveground pipeline. In the case of failure of a high-pressure underground pipeline that causes a large leak, the pressure will fall rapidly, releasing a large quantity of energy. This energy will cause the soil above to be ejected, potentially resulting in large damages to structures and loss of lives.

Accidents in densely populated areas represent a greater risk both in terms of probability and severity. This fact requires a larger investment in security and ongoing monitoring of

The main aspects that influence the amount of CO2 that can escape during an accident are: internal diameter of the pipeline, size of the hole, operating temperature and pressure and

Because CO2 is heavier than air, when released in large quantities it behaves differently than gases that are lighter than air. The release of CO2 occurs in the form of a cloud that moves near the ground and its progress depends closely on the local topography and weather.

The most important aspect to be analyzed is the impact of CO2 leaks on human health. In this respect, the concentration and exposure time are the two factors that must be assessed. A CO2 concentration of 150,000 parts per million (ppm), or 15% by volume, can cause a person to lose consciousness in less than one minute. Exposure for one hour to concentrations between 100,000 and 150,000 ppm can cause mortality ranging from 20% to

When injected, the CO2 is less dense than the saline fluids of the reservoirs, so it can migrate to other geological formations or to the surface. The escape to the atmosphere, besides causing risks to human health and the environment in nearby areas, also obviously reduces the effectiveness of the effort to control GHG emissions intended by the CCS project in the first place. The leakage of high concentrations to the atmosphere can have catastrophic

urban expansion in the areas through which the pipeline passes.

necessary pipelines.

Corrosion;

failure can be the result of:

 Construction defects; Materials defects; Soil movement;

Operational errors; and

distance between shut-off valves.

90% (Koornneef et al., 2010).

effects on the local biota.

**3.3 Risk of leakage to the atmosphere** 

 CO2 leakage to the surface can occur because of: Pre-existing geological fractures or faults;

Human activities in surrounding areas.

manage the risk of a CCS project. This imposes the need for an adaptive intelligence able to accompany this dynamic interplay of factors.

The complexity of managing the risks of a CCS process depends on a series of aspects inherent to each project, among them the following:


The varying combination of these aspects will determine the analyses that must be undertaken.
