Quantitative risk assessment is required for SCS projects in order to fully capture their complexity, potential impacts, and monitoring requirements over long timeframes.
The subsurface characterization of potential CO2 storage sites begins with the evaluation of current risks such as pore volume and injectivity. Many SCS site selection studies have used strategies for assessing current risks that were developed in the oil and gas industry, including common risk segment mapping and the geological chance of success. These approaches typically use a probability scale of 0 to 100% (see Figure below).
The identification of future risks, such as storage effectiveness and CO2 retainment, should also begin in the early stages of a project. The frequency of these potential future events should be assessed as the probability of the event occurring in any single year. The probability values in this context are far lower than those used in oil and gas risk assessments, hence an expanded log scale is more appropriate (see Figure below).
It is possible to estimate the frequency of some types of future events using empirical data. Several papers have been published that contain data regarding the rates and annual frequencies of these events. Other analogous frequency data that could be used to estimate base rate event probabilities include seismicity data, published reports of hazards and accidents, industry and government information, and detailed reviews of SCS projects.
