The latter should assess risks to the capacity, injectivity and containment of candidate storage sites, where well integrity represents one type of risk to storage containment. This step should involve: defining the goals and objectives of the well integrity risk assessment; defining responsibilities for and within the risk assessment process; defining the specific inclusions and exclusions; defining the risk assessment in terms of time and location; defining the relationship between the risk assessment process and the overall development of the CO2 geological storage project; defining the risk assessment methodologies; dentifying and specifying the decisions that have to be made prior to milestone M2; 2. 1. 3. Defining risk criteria Risk criteria for evaluating the significance of well integrity risks need to be defined by the project developer. The risk criteria should reflect the objectives and context for the risk assessment. Adequate consideration should be given to the time and resources available, stakeholder views and risk perceptions, and the applicable legal and regulatory requirements. The risk criteria chosen should be continuously reviewed. Prior to specifying risk criteria, the categories for which risks will be evaluated shall be defined.
These include: human health and safety; environmental protection; legal and regulatory compliance; cost; project schedule; reputation; well integrity (functional) performance. The following points should be considered when defining risk criteria for well integrity assessments: the categories of risk for the CO2 geological storage project established in the ‘screening basis’ step of ; the nature and type of causes and consequences that can occur and how they will be measured; how likelihood will be defined (for example qualitatively or as a quantitative probability); the timeframe of interest; ow the level of risk is to be determined; the level at which the risk becomes acceptable or tolerable; whether combinations of multiple risks should be taken into account and, if so, how and which combinations should be considered (for example leakage pathways composed of multiple failures). In order for the risk criteria to be adequate to support a storage site selection decision they should: be suitable for decisions regarding risk reducing measures to levels as low as reasonably practicable; be suitable for communication; e unambiguous in their formulation; not favour any particular concept solution explicitly nor implicitly through the way in which risk is expressed. In addition, risk criteria for CO2 leakage rates related to existing wells should be consistent with the overall storage site containment criteria established in Section 2. 1 (‘Screening basis’) of . Note: Temporal, spatial, volumetric and rate limits for CO2 leakage should be finite and quantifiable to allow for effective risk management.