6.1.2 CO2 Storage

Directives and regulations on closure and post-closure for CO2-storage are still in development. Therefore there are only a few regulations dealing with the abandonment of CO2-storage wells, which are mostly amendments and further recommendations of the already existing subsoil acts and directives concerning hydrocarbon exploration wells (due to the similarities of the topic).

International Regulations

The IEA Carbon Capture and Storage: Model Regulatory Framework requires for the abandonment of CO2 storage wells a description of the location, the condition of the wells, applied plugging procedures and integrity testing results for every possibly effected well. Also a description of the decommissioning, as required by the relevant authority, is wanted.

The OSPAR and London Convention amendments related to CO2-storage well abandonment state: "Particular attention should be paid to integrity of the wells. Over the longer term, the risk assessment should also address any change in the integrity of the seal and of the plugs in the abandoned wells and might include the effects of CO2 dissolution and mineralization". "Special care should be taken to use sealing plugs and cement that are resistant to degradation from carbonic acid" (London Protocol, 2006b). In 2007 the OSPAR Convention made amendments for environmentally safe storage of CO2 where they excluded the injection of CO2 in the water column and the disposal onto the seabed.

European regulations

EU directive 2009/31/EC notes as a requirement that "the site has been sealed and injection facilities have been removed". Guidance Document 3 (EC, 2011c) mentions the necessity of appropriate materials and practices without any further details on procedure or plugging.

The SINTEF Petroleum Research Report on "Ensuring well integrity in connection with CO2 injection" (Randhol et al., 2007) stated that NORSOK D-010 standard could fundamentally serve as basis for setting guidelines for CO2 storage wells. However, it criticised some topics in NORSOK D-010 standard in relation to CO2 applications: mainly: (1) material selection of barriers are too general and specific details missing (type of cement etc.), (2) well barriers: no plug placed in cap rock - insufficient for wells exposed to CO2, (3) completion string: NORSOK leaves tubing in place also for abandoned wells - inadequate for CO2 applications, (4) temporary well abandonment: no time frame defined, (5) monitoring guidelines missing for permanently abandoned wells

Germany

In 2012 the EU Directive 2009/31/EG was implemented in Germany as the Federal Law regarding the Application of CCS in Germany ("Demonstration der dauerhaften Speicherung von Kohlenstoffdioxid (Kohlendioxid-Speicherungsgesetz - KSpG). Before the abandonment of CO2-storage wells it is required to submit a decommissioning plan including a description of the steps taken to prevent any leakage as well as a post-closure plan with monitoring concepts updated every 5 years. These updates lead to renewed assessment of long-term safety as well as risk and ensure an up-to-date technical maintenance. The operator has the duty to provide financial security to the authority. He will be able to transfer the liability of the storage site to the competent authority at earliest 40 years after decommissioning.

USA

EPA UIC regulations state that before placing plugs the well has to be flushed with a buffer fluid and the operator has to determine bottom reservoir pressure and perform mechanical integrity test. A plugging plan, which has to contain a bottom hole reservoir pressure test, mechanical integrity test and number and material of plugs, as well as placement of the plugs and which method was used needs an approval by the authority. There are no specifications on required materials or required tests, as they want to acknowledge the variety of available/appropriate methods and materials. The only state requirement is the compatibility of plugs with injectate to eliminate potential degradation of plugs over time.

IOGCC guide regulations state that the operator needs an approval before the plugging of wells. It also states: "Well-casing shall be cut off at a depth of 5ft below surface and a steel plate shall be welded on top identifying well name and that it was used for CO2 injection". After well plugging, the surface installations must be removed and the site restored to its original state as far as possible.

Australia

The Offshore Petroleum Amendment requires the operator to remove all property brought to the site and to demonstrate to the Minister the removal and plugging of wells in a way that minimises quality damage to the petroleum bearing formations and maintains the suitability for permanent storage of greenhouse gas substances.

The "Queensland Greenhouse Gas Storage Regulation 2010" further requires a report when decommissioning CO2 storage wells, which must include:

  • Details on the installed well equipment with diagrams showing their dimensions and features;
  • Full description of equipment that may cause a hazard to underground mining operations;
  • Surveyed location of any prescribed equipment;
  • Method of the cementing operations (location and type of plugs, plugging intervals, volume/type of cement, occurrences while cementing (cement loss and remediation));
  • Description of any other performed abandonment procedures;
  • Details of activities performed on the well to assess potential risks to safe and efficient underground mining.