Guidance document 3
Criteria for transfer of responsibility to the competent authority

EUROPEAN COMMISSION
Directorate-General for Climate Action
This document has been prepared with the assistance of DNV Netherlands B.V. under contract to theEuropean Commission (Service contract No 090203/2022/881796/SER/CLIMA.C.2)
It has also greatly benefited from discussions with, and information supplied by, experts from Member
States within the framework of the Expert Group on the geological storage of carbon dioxide and with key
stakeholders during a targeted stakeholder consultation. DG CLIMA gratefully acknowledges contributions
from other Commission departments (COMP, ENER, ENV, MARE, GROW, REGIO, SANTE, RTD, JRC,
SG and SJ) to the work to finalise the guidance documents.
Email:

CLIMA-CCS-DIRECTIVE@ec.europa.eu

European Commission
B-1049 Brussels

EUROPEAN COMMISSION

Guidance document 3
Criteria for transfer of responsibility to the competent authority

Directorate-General for Climate Action
2024

The aim of this guidance document is to contribute to a better understanding of the requirements of Directive
2009/31/EC on the geological storage of carbon dioxide. It has been prepared by the European Commission
on the basis of the views and knowledge provided by stakeholders. The purpose of this guidance is
explanatory and illustrative. It does not create any rights or obligations.

Manuscript completed in July 2024

This document has been prepared for the European Commission however it reflects the views only of theauthors, and the European Commission is not liable for any consequence stemming from the reuse of thispublication.
© European Union, 2024

The reuse policy of European Commission documents is implemented by Commission Decision
2011/833/EU of 12 December 2011 on the reuse of Commission documents (OJ L 330, 14.12.2011,
p. 39). Unless otherwise noted, the reuse of this document is authorised under a Creative Commons
Attribution 4.0 International (CC BY 4.0) licence (https://creativecommons.org/licenses/by/4.0). This meansthat reuse is allowed provided appropriate credit is given and any changes are indicated.

Guidance document 3

Contents

1.

Revision history ....................................................................................... 6

2.

Purpose and scope of guidance documents ......................................... 7

3.

Legislative context................................................................................... 8

4.

Guidance on compliance with legislative requirements ...................... 94.1. Article 18(1)(a): Complete and permanent containment ........................ 9
4.1.1. Article 18(2)(a): Conformity with models ................................................... 9
4.1.2. Article 18(2)(b): Absence of any detectable leakage ............................... 11
4.1.3. Article 18(2)(c): Evolution towards long-term stability .............................. 124.2. Article 18(2) Transfer report ................................................................. 13
4.3. Article 18(1)(b) Minimum period for post-closure monitoring ............... 15
4.4. Article 18(1)(d) Site sealing and removal of injection facilities ............. 15
4.5. Transfer of data and models ................................................................ 165

1. Revision history
Key changes since the previous version•

Clarifications on obligations that are being transferred.

•

Clarification on interpretation of the terms ‘permanence’ and ‘long-term stability’.

•

Guidance added on how to reach agreement on a shorter closure period.

•

Guidance added on transfer requirements for sites not principally relying on structural trapping.

•

Clarifications on requirements for monitoring facilities for site sealing.

62. Purpose and scope of guidance documents
This guidance document (GD) forms part of a set of guidance documents as follows:●

Guidance document 1: CO2 storage life cycle and risk management framework;●

Guidance document 2: Characterisation of the storage complex, CO2 stream
composition, monitoring and corrective measures;●

Guidance document 3: Criteria for transfer of responsibility to the competentauthority;●

Guidance document 4: Financial security and financial contribution.

The aim of these GDs is to improve understanding of the requirements of Directive
2009/31/EC on the geological storage of carbon dioxide (the ‘CCS Directive’) and giveindications on how it can be implemented. They should therefore facilitate a correct anduniform application of the CCS Directive across the EU. The guidance does not represent
an official position of the Commission and is not legally binding. The binding
interpretation of EU legislation is the exclusive competence of the European Court ofJustice that can make final judgments concerning the interpretation of the CCS Directive.
GD 3 addresses transfer of responsibility from a site operator to the competent authority
or authorities of Member States under Article 18(1) for ‘all legal obligations relating tomonitoring and corrective measures pursuant to the requirements laid down in the CCS
Directive, the surrender of allowances in the event of leakages pursuant to Directive
2003/87/EC and preventive and remedial action pursuant to Articles 5(1) and 6(1) of
Directive 2004/35/EC’.
Note: See GD 1, Section 2.4, for interpretations of the main defined and non-definedterms used in the CCS Directive.

7

3. Legislative context
After a storage site is closed, the operator remains liable for monitoring, reporting, taking
corrective measures and surrendering allowances in the event of leakage, until theseobligations are transferred to the competent national authorities in accordance with
Article 18 of the CCS Directive.
This guidance clarifies the following obligations:●●

Article 18(1)(a), 18(1)(d) and 18(2)(a)-(c): Submission of a transfer report
documenting that the following conditions have been met:oall available evidence indicates that the stored CO2 will be completely andpermanently contained;othe storage site has been sealed and the injection facilities have been
removed;othe actual behaviour of the injected CO2 conforms to the modelledbehaviour;othere is no detectable leakage;o

the storage site is evolving towards a situation of long-term stability.

Article 18(1)(b): A minimum period determined by the competent authority has
elapsed. This minimum period is to be no shorter than 20 years, unless theauthority is convinced that the criterion in 18(1)(a) is met before the end of that
period.

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4. Guidance on compliance with legislative requirements
4.1.

Article 18(1)(a): Complete and permanent containment

This section provides guidance on the interpretation of Article 18(1)(a) by clarifying what
may be required to demonstrate permanent containment and to meet at least the three
conditions listed in Article 18(2):a)

the actual behaviour of the injected CO2 conforms to the modelled behaviour;b)there is no detectable leakage; andc)the storage site is evolving towards a situation of long-term stability.

Note: Third-party certification of CO2 storage is an emerging field. Such certification canhelp establish confidence that storage complies with the conditions for transfer of
responsibility. The CCS Directive does not prevent the competent authority fromoutsourcing evaluation of compliance to third parties. Nor does it suggest that operators
should seek third-party certification as part of the process for transfer of responsibility.

4.1.1. Article 18(2)(a): Conformity with models
Any assessment of containment permanency will be based on models and observations
obtained through monitoring. The models and monitoring used to demonstratecompliance with Article 18(2)(a) should have been approved by the competent authority
as part of the storage permit and subsequent updates (see GD 2), in accordance with
Articles 9 and 11. The modelling and monitoring should provide sufficient understandingof the containment performance of the storage complex to assess its future developmentwith a high degree of confidence. The acceptable margin of conformity between models
and observations should take account the modelling approach and site-specificcharacteristics, and may be decided by the competent authority in consultation with theoperator. Since the behaviour of the injected CO2 will be influenced by other activities
going on in the same hydraulic unit, the competent authority should ensure that site
operators have enough data about other activities to accurately model the CO2 behaviour
and the response of the storage complex. The following guidance can help determine
compliance with Article 18(2)(a).
●●Model validity. A model can be considered reliable and valid if:orecent history-matched models have provided forward predictions thatmatch, to an acceptable margin, observed behaviour within estimateduncertainty ranges for key containment performance parameters; andobackcast predictions obtained using the final history-matched dynamic
models are consistent, to an acceptable margin, with the observed
behaviour throughout the project.

Model changes. The competent authority should review the changes made to
the model and the model’s projections over the last few years before the transfer
to verify that the model has been able to match recent history without significant
9changes to either the static geological model or the dynamic model derived fromthe static model.
The static geological model should remain significantly unchanged for 5 years prior totransfer. This 5-year period may start before closure (definite cessation of CO2 injection).
The operator should specify the range of uncertainty in the key parameters for the static
geological model. Altering key parameters outside the specified range of uncertainty
would constitute a significant change to the model.
Significant model changes are changes that alter the understanding of the storage
complex containment performance and corresponding flow, geochemical andgeomechanical behaviour in ways that invalidates any of the results of previous risk
assessments for the storage project. Tuning model parameters such as permeability,
porosity, elastic properties or rock strength properties in ways that do not substantiallyalter the understanding of the performance of the storage complex is not considered to
be a significant model change. An example of a significant change would be theintroduction of a previously unmapped fault into the static geological model that either
impacts capacity through compartmentalisation or represents a previously unidentified
leakage pathway.
The judgement of significant change should be based on the characteristics of theindividual storage complex, the specific nature of the change and developments inscientific knowledge about site characterisation and dynamic modelling.

1●

Modelling projections. Modelling projections should demonstrate that the CO2
will remain contained through various trapping mechanisms in the storage
complex over the modelled time period, and that there is no significant risk of
future leakage1. To this end, it should be demonstrated that model realisations
indicating a significant risk of future leakage can be rejected with confidence. The
operator must demonstrate a trend showing that historical model predictions for
key parameters, such as CO2 plume migration, CO2 dissolution and pressure,match observations within acceptable uncertainty ranges. It must also
demonstrate that the need to recalibrate static and dynamic models to achieve
an adequate history match has been reduced or eliminated. The acceptable
range for the various parameters should take account of site-specificcharacteristics and may be decided by the competent authority in consultation
with the operator.

●

Documentation. Documentation of the predictive capability of the models andhistory matching for the storage site should cover:In the CCS Directive, ‘significant risk’ means a combination of a probability of occurrence ofdamage and a magnitude of damage that cannot be disregarded without calling into question
the purpose of the Directive for the storage site concerned. The ‘magnitude of damage’ thatcan be caused by individual leakage risk scenarios is site-dependent, and includes both thepossible amount of leakage that can occur related to the risk scenario and the impact onhuman health or the environment resulting from the possible leaked amount. While this GD
does not make a distinction between the possible impact of leakage in on- and offshore
environments, the nature of the impact on human health and the environment is generally
different.

10

ohow monitoring data have been collected and interpreted, including
measurement errors and confidence intervals for all monitored
parameters;ohow site-specific geological models and the associated geomechanical,
geochemical and flow simulation models have been calibrated throughhistory matching and other adjustments; andohow site performance has evolved relative to the predictions, based on
available monitoring data. This could include:
1) injection pressures and volumes at each injection well;2) the measured pressures throughout the storage complex;3) the vertical and horizontal location and movements of any CO2
plumes;4) changes in the composition of formation fluids and geochemical
reactions that have occurred with rocks in the storage complex;5) changes in processes within the storage complex that impact the
security of storage, such as dissolution and mineralisation;6) any observed earth deformation and seismicity;7) an interpretation of the fate of displaced formation fluids; and
8) a description of the estimated fraction of injected CO2 that istrapped by the various trapping mechanisms, i.e. structural
buoyancy trapping, residual saturation trapping, dissolution,mineralisation and adsorption.

4.1.2. Article 18(2)(b): Absence of any detectable leakage
A key aspect of containment is that there is no detectable leakage from the storage
complex, including leakage through geological or man-made pathways (see GD 1).
‘Detectable’ is interpreted to mean ‘can be detected by direct monitoring observations
based on the approved monitoring plan or can be inferred from modelling that conforms
to monitoring data’ in line with GD 1 (Section 2.4).
All monitoring technologies have limitations in terms of spatial and temporal resolution
and sensitivity to changes. Therefore, approval of a monitoring plan implicitly gives
approval to an accepted detection limit. While a broader or more extensive monitoring
programme may improve this limit, it comes at additional cost. The approved monitoringplan for evaluating compliance with Article 18(2)(d) should therefore be clearly set out inthe updated and approved post-closure plan in line with Article 17(3)(a) and (c).
There should be no detected leakage for a 10-year period immediately before the timeof transfer. This period can start before closure (definite cessation of CO2 injection). The
operator can present a case to the competent authority for a shorter period if a leakage
event has occurred during an extended period with no other leakage, and there is very
low likelihood of future leakage along the same pathway. This could apply, for instance,11

if leakage occurred during a well workover operation or well abandonment operation,and the well has subsequently been properly sealed.
The specific metrics for determining the absence of leakage from the storage complex
would need to be selected by the competent authority, in consultation with the operator
based on site-specific characteristics. Examples of metrics that could be used byoperators to assess the absence of detectable leakage include:●

well integrity - no well integrity issues2;●

overburden monitoring - no sign of abnormal or unexpected pressure or otherconditions associated with leaks to zones above the storage complex;●

conformity monitoring - no detection of any remaining CO2 plume outside thestorage complex or outside any structural barrier within the storage complex;●

groundwater and biosphere3 monitoring - no detection of CO2 above expectednatural levels.

The absence of leakage should be determined relative to a pre-project baseline, or, if
leakage has occurred, a baseline representing the state of the environment 10 years
prior to the evaluation of compliance with Article 18(2)(b). The baseline should provide areference against which project performance is measured. The baseline should identify
and describe receptors that may be impacted by leakage so that changes attributable tothe storage project can be differentiated from changes that are not attributable to theproject. The baseline may include characterisation of receptors outside the storage
project area that are exposed to environmental factors similar to those that exist within
the area.

4.1.3. Article 18(2)(c): Evolution towards long-term stability
Evolution towards a situation of long-term stability may be indicated when:a)modelling of continued evolution of the storage complex (dispersion of any
remaining CO2 plume, pressure influence from the storage project, andgeochemical reactions) does not show any significant risk of future leakage
of CO2 or negative effects on human health or the environment4; and2

For wells that have not been sealed following closure, well integrity issues can be detectedby well logs or geophysical monitoring technologies (e.g. seismic, electrical, gravity orelectromagnetic surveys). Well integrity issues for wells not available for entry can bedetected by groundwater and biosphere monitoring.

3

ISO 27914:2017 defines the biosphere as the ‘realm of living organisms including theatmosphere, on the ground surface and in soils, in oceans and seas, in surface waters suchas rivers and lakes, and in the subsurface above the storage complex’.

4

Evolution towards a situation of long-term stability includes situations where a CO2 plumecontinues to move or disperse, but where there is confidence that trapping mechanisms will
be effective, i.e. there are no significant risks of future leakage or negative effects onhuman health or the environment.

12

b)

key monitored parameters are within a predetermined range or trend of the
future stable values (as predicted by modelling).

Model realisations indicating a significant risk of future leakage should be rejected withconfidence. Sensitivity studies exploring alternative model realisations should be
performed, with a firm conclusion that model realisations indicating possible leakage are
improbable. Further changes in any remaining CO2 plume should not lead to contact withnew potential leakage pathways for which confidence in barriers to leakage has not been
firmly established, such as legacy wells without verified well barriers. For geochemical
modelling, the emphasis should be on providing evidence to exclude the possibility ofgeochemical reactions with wells or sealing geological formations that might have amaterial impact on the risk of leakage. Pressure in the injection zone will generally be on
a declining trend after injection has ceased. This also implies the risk of leakage caused
by pressure influence to, e.g. wells and faults will be gradually reduced.
The key monitored parameters that should be considered for assessing evolution
towards long-term stability are:●pressure within the storage complex;●

movement of any remaining CO2 plume and residual CO2 saturation; and●integrity of materials used to construct or seal the wells.

The acceptable range of further changes for key monitored parameters should bedetermined by the operator on a site-specific basis, and noted at the time of the storage
permit, subject to any required changes based on actual operational history (i.e. toaccount for any corrective measures, updates, etc.). Evidence must also be provided tothe competent authority to show that corrective measures carried out during theoperation and post-closure periods will remain effective after transfer.

4.2. Article 18(2) Transfer report
The transfer report should include a description of all the parameters monitored during
the post-closure, pre-transfer period and should be based on the updated post-closure
monitoring plan (see GD 1). Table 1 shows documentation that the competent authority
may require operators to supply in the transfer report to show that the condition in Article
18(1)(a) has been met.
Table 1: Required documentation in transfer report.
Evidenceforcomplete
permanent storage
Conformity with models

andRequired documentation from the operator

1) For at least a continuous 5-year period immediately before
the transfer, there has been no need to significantly change the
3D static geological model assumptions for the characteristicsof the storage complex during history matching exercises
incorporating parameters monitored at regular intervals.

132) Demonstration that backcast and forecast predictions
obtained using the final history-matched dynamic models are
consistent with observed behaviour, where any observed
discrepancies do not impact confidence in storage security.
Absence of any detectable leakage

For at least a continuous 10-year period immediately before
transfer, show that:1.

integrity of all wells (monitoring and injection) remains without
any leaks or unexpected deterioration or damage;2.

monitoring data based on the approved monitoring plan
indicates that there is no leakage.

Evolution towards long-term stability 1.

The models project stability of any remaining CO2 plume within
the storage complex.

2.

Key monitored parameters are within a predetermined range ofthe future stable values.

The time frames given in Table 1 are indicative and need to be specified by thecompetent authority. The time periods referred to may start before the closure of the site.
In addition to the documentation listed in Table 1, the transfer report may also provide
the competent authority with a final summary of the geological storage activities thathave taken place in the storage complex for posterity. This could include the following
items (based on Chadwick et al., 2006 and ISO 27914):●

narrative history of the storage site activities, including site characterisation,
injection facility construction, operations, any corrective measures, andmonitoring;●a revised, finalised storage complex characterisation report, including informationfrom the final static and dynamic models, and a description of historical storage
performance relative to iterative predictions from modelling and simulations;●a quantification of the modelled contribution of the various trapping mechanisms5
to deliver permanent containment at the time of transfer and evolution in the
future;●an updated project risk database showing how individual risk scenarios have
evolved throughout the project, including a description of the reasons for
upgrading or downgrading risks; and●compilation of results and conclusions drawn from monitoring, modelling and risk
assessments to help demonstrate that the criteria for transfer of responsibility
have been met, including proof that applicable trapping mechanisms are effective
and that injection facilities have been removed.

Many of the items listed above may be reported to the competent authority as part of theannual reporting as required under Article 14. In that case, the transfer report could referto the appropriate annual reports (put in an annex).

5

Structural buoyancy trapping, residual saturation trapping, dissolution, mineralisation andadsorption.

14

4.3. Article 18(1)(b) Minimum period for post-closure
monitoring
Article 18(1)(b) of the Directive states that the post-closure, pre-transfer phase should
be at least 20 years, unless the competent authority is convinced that all available
evidence indicates that the stored CO2 will be completely and permanently contained
before the end of that period. On the other hand, the authority can always determine alonger period than 20 years if it considers this appropriate.
To facilitate a possible handover prior to the end of a 20-year post-closure period, it issuggested that the operator specify in the post-closure plan quantitative key performanceindicators used to measure compliance with the criteria for transfer (Article 18(1)(a) and18(2)(a)-(c)). These indicators should be discussed and agreed with the competentauthority. This can be done as part of the evaluation of the provisional post-closure plan
(in accordance with Article 7(8) and Article 9(7)) and its subsequent update and approval
prior to closure in accordance with Article 17(3). The quantitative key performanceindicators should be based on the site-specific context and consider: (i) the evolution ofcontainment risk over time; and (ii) the effect of modelling and monitoring during the
project on constraining the forecast bounds of any residual leakage risk.

4.4. Article 18(1)(d) Site sealing and removal of
injection facilities
The updated post-closure plan should contain details of how a site should be sealed andhow injection facilities at the site should be removed6. However, the transfer report may
note any additional changes to this updated plan based on any new information gatheredon the approach to the site sealing and removal of the injection facilities.
Under Article 18(3), the draft decision approving the transfer of responsibility mustspecify the method used for determining that the site has been sealed and injection
facilities have been removed. The draft decision must also specify any updated
requirements pertaining to Article 18(1)(d) (e.g. transfer of data and any other legal
issues). The competent authority may consult the operator and may approve a methodsuggested by the operator if the authority considers it suitable for determining
compliance with the conditions in Article 18(1)(d), as well as any updated requirements
for the sealing of the site and the removal of injection facilities.
The following requirements should be considered when determining if the site has been
properly sealed:●

6

Any well under the responsibility of the operator which penetrates the storage
complex, or which has been identified as a CO2 migration risk, and which will not

The CCS Directive does not explicitly specify any requirements for removal of monitoring
facilities. The competent authority may decide or request that certain monitoring facilities orwells are not removed or sealed so that they can be used for post-transfer monitoring inaccordance with Article 18(6).

15be used for post-transfer monitoring should be sealed using appropriate bestpractices and materials7. The sealing of wells should take into account possible
geochemical reactions and geomechanical effects that could have an impact on
the integrity of well materials. Guidance on evaluating legacy wells as part of sitecharacterisation, including legacy decommissioned wells, is provided in GD 2
Section 3.3.7.
●

The monitoring facilities to be maintained in order to continue monitoring beyond
transfer or for other nearby storage sites should be determined based on the final
site-specific risk assessment. This should weigh the potential leakage risk fromany penetration of the seals above the injection zone against the potential risk
reduction from maintaining the monitoring facilities.

The competent authority will be responsible for carrying out any post-transfer monitoring
and verification. The financial contribution (see GD 4) must cover at least the cost of any
such monitoring and verification for a period of 30 years after injection ceases. Monitoring
facilities that will not be used post-transfer should be removed and the surface areas
reclaimed.

4.5. Transfer of data and models
In connection with the transfer of responsibility, the operator will have to transfer data
about the site to the competent authority. This is in addition to the information in thetransfer report. There are no specific provisions on data retention and ownership in the
CCS Directive.
Issues regarding data retention, availability and ownership will need to be resolved byeach Member State and should be set out in the storage permit. Some data and analysis
will be provided to the competent authority as part of the regular reporting requirement.
However, once the responsibility is transferred to the competent authority, it is expectedthat the operator will also hand over all of the relevant documents and raw data (includingcore samples, drill cuts, construction material samples, and other key material samples
extracted from the site).
Member States may also set requirements and procedures for transfer of relevant
models, including the final static and dynamic models. This will enable the competentauthority to make well-informed intervention decisions post-transfer if required, or to
make the models available to other operators working in the same hydraulic unit, or who
may perform such work in the future. To this end, the Member State should clarify time

7

Member States may review and use existing abandonment procedures for oil and gas
wells, if they are deemed sufficient. Such practices are described in documents such as
NORSOK D-010:2021 Well integrity in drilling and well operations, and ISO 16530-1:2017
Petroleum and natural gas industries - Well integrity - Part 1: Life cycle governance.
Additional guidance specific to abandonment of wells for CO 2 storage operations can befound in ISO 27914:2017 – Carbon dioxide capture, transportation and geological storage –Geological storage Clause 7.8, DNV-RP-J203 Geological storage of carbon dioxide,
Section 7, and OEUK Guidelines: Well Decommissioning for CO2 storage, 2022.

16

frames for ownership of proprietary models in line with intellectual property andcommercial competition rules.
In setting time frames for proprietary ownership of data, Member States should balance
the rights of the operator against the potential to help to improve knowledge of reservoirs
and their performance over time, based on commercial rules and/or applicable practicein the oil and gas industry. Within the European Union, the competent authorities in each
Member State could also consider exchanging data with each other in order to learn fromexperience in other countries.

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