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This chapter introduces a "scenario approach," which is used as a methodology for the long-term safety assessment of underground CO2 storage and to demonstrate its applicability in an example of safety assessment. This developed methodology consists of three main parts-scenario analysis, model development and consequence analysis. The scenario analysis focuses on a comprehensive inventory of risk factors-features, events, and processes (FEPs) and subsequent selection of the most critical factors that will be grouped into discrete CO2 leakage scenarios. Quantitative physico-mathematical models need to be developed to enable a quantitative safety assessment of the scenarios in the consequence analysis. The developed method was successfully applied to two virtual settings in the southern part of the North Sea. In these two settings two leakage scenarios are considered, leakage up a fault and through a failed well. © 2005 Elsevier B.V. All rights reserved.

The RECOPOL project is an EC-funded research and demonstration project to investigate the technical and economic feasibility of storing CO2 permanently in subsurface coal seams. This is considered to be an option for CO2 sequestration, which will be required to meet the Kyoto protocol. The main aim is to demonstrate that CO2 injection in coal under European conditions is feasible and that CO2 storage is a safe and permanent solution before it can be applied on a larger scale in a socially acceptable way. An international consortium of research institutes, universities and industrial partners is carrying out the project activities. This is the first field demonstration experiment of its kind in Europe. The development of the pilot site in the Upper Silesian Basin in Poland began in summer 2003. One of the existing coalbed methane wells was cleaned up, repaired and put back into production. A new injection well was drilled at 150 m from the production well, the distance being based on the available amount of CO 2 and project time. After completion of the well with casing, cementing and perforations, the perforated zones were tested. Activities in autumn 2003 included the finalizing of the injection facilities. Production was started in the first half of June 2004 to establish a base line gas production without CO2 injection. First injection tests took place in the first week of July 2004. During the injection period the process was monitored to assess any potential, although unlikely, leakage of CO2 to the surface. Copyright 2005, Society of Petroleum Engineers.