CO2CARE, CO2 Site Closure Assessment Research : D5.4 Best Practice Guidelines

British Geological Survey. 2013 CO2CARE, CO2 Site Closure Assessment Research : D5.4 Best Practice Guidelines. British Geological Survey, 52pp. (FP7-ENERGY-2010-1)

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This report presents a set of pragmatic and workable generic procedures, suggested best practices and other recommendations and observations for the safe and sustainable closure of geological CO2 storage sites. These have been distilled from the results of the CO2CARE project and represent the most important messages that will be of benefit to Regulators, storage site Operators and other stakeholders. Key observations and recommendations are set out below. Transfer of responsibility for all legal obligations for a storage site from the Operator to the Competent Authority (CA) marks a radical change in the balance of responsibilities between stakeholders in a storage project. The CA is ultimately the representative of the public, and this implies an acceptance by the public of the benefits and associated liabilities. Acceptance of the Transfer Report and transfer of responsibility for all legal obligations for the site to the CA marks the end of a process that began with site selection and a permit application by the Operator many years previously. It is vital that a relationship based on transparency and openness should have developed between the Operator and Regulator during that period, to build mutual confidence into the regulatory process and, ultimately, the transfer of responsibility. Continuity of knowledge through changes of personnel should also be ensured. This, together with the regular reporting requirements that most jurisdictions require (e.g. those required under the EU Directive) should help to ensure that the transfer of responsibility proceeds smoothly and to the satisfaction of all parties involved. When CO2 injection at a storage site has ceased, the storage site is described in the EU CO2 Storage Directive as being closed and the project life cycle enters the post-closure phase, leading to transfer of responsibility. During the post-closure phase the wells will not necessarily be sealed immediately, the site will continue to be monitored and reservoir management will continue, in accordance with the project risk assessment and management plan, which will have been updated at site closure. The main purpose of reservoir management in the post-closure phase is to demonstrate that the key regulatory requirements for transfer of storage site liability to the Competent Authority have been met. In the EU CO2 Storage Directive these are: • Observed behaviour of the injected CO2 conforms to the modelled behaviour • No detectable leakage • The storage site is evolving towards a situation of long-term stability Meeting these criteria involves demonstrating understanding of reservoir processes, the ability to make robust predictions of future behaviour and providing assurance against leakage. Demonstrating conformance between predictive models of reservoir performance and monitoring observations is technically challenging because a unique and perfect match is near-impossible to achieve. CO2CARE recommends that conformance is based on demonstrating that predictive modelling capability increases systematically with time as monitoring data is progressively acquired. This indicates that storage processes are well understood and the modelling approach is robust. If predictive modelling is robust, uncertainties will progressively reduce as more monitoring data is acquired through time. Nevertheless it is necessary to maintain a sufficiently wide range of predictive scenarios, such that any reasonable outcome will fall within it.

Item Type: Publication - Report
Funders/Sponsors: European Commission Seventh Framework Programme
Additional Information. Not used in RCUK Gateway to Research.: Report also available for free download from
Date made live: 02 Feb 2016 08:36 +0 (UTC)

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