7.1 Overall Risks to the CCS Project

An initial risk assessment was performed during the Feasibility Study stage for the Getica CCS Demo Project. A preliminary risk register and risk matrix were developed.

A systematic identification of risks was undertaken, taking into account the FEED, Engineering, Procurement and Construction (EPC), operation and post-operation phases. The risk assessment has included all of the potential technical and non-technical risks associated with CO2 capture, transport and storage, including surface facilities and existing wells in the storage site area. These risks could significantly impact the CCS project in areas such as performance (technical, schedule, financial) and constraints to be met (HSE, public acceptance, compliance with regulations), for example.

Of the 69 risks assessed, 18 were classed as critical to the CCS project requiring near-term mitigation measures. These risks were related to uncertainties associated with:

  • overall costs of the project;
  • by-product management;
  • the capture technology, and potential technical issues associated with the scale-up from pilot to demonstration phase;
  • landowner approvals; and
  • the performance of the CO2 storage site in terms of containment and injectivity.

Although the results of this first round risk assessment show there are some potentially high risks, these can be reduced by relatively simple mitigation actions such as:

  • more effective communication;
  • acquiring more accurate, site-specific storage data;
  • performing additional laboratory tests on the data collected; and
  • conducting further modelling and simulations on pipelines and geological storage.

The residual risk estimation shows that the risk levels could be significantly reduced.

Other (non-technical) risks have been identified, such as insufficient funding, liability risks, possible conflicts of interests with the oil and gas industry, HSE risks and public acceptance related issues. However, issues such as the health risk on local population or public acceptance have been indirectly taken into consideration through the focus put on the containment performance factor. The possible conflicts of interest with the oil and gas industry will need to be addressed in detail to define its impact on the project development and must be evaluated when the proper procedures for granting the storage authorisation will be elaborated by the National Agency for Mineral Resources (NAMR), the Competent Authority for storage.

Since this is the exploratory phase of the project, there are currently some gaps in the level of understanding of the project. These gaps create uncertainty in the risk ratings. Quantitative risk assessment will need to be performed on some risks, mainly in the technical area. This will not be appropriate before project definition of the system and its sub-systems is obtained. The uncertainties can, and will be reduced by gathering more data and performing various rounds of modelling, simulations, and risk assessments.

As a consequence, the results of this initial risk assessment are not final and will be updated periodically as more data becomes available. It is essential to consider it as a dynamic process and to update the assessment periodically to reflect new data and/or changes.

7.1.1 Assessment of Technical Storage Risk

In general for CCS projects, storage is perceived to have the greatest uncertainty. This section considers storage risks in more detail. Preliminary risk and performance assessments were conducted on the two candidate storage sites (Zones 1 and 5). These showed that, based on current available data, subsurface storage of CO2 could be possible in either of them. However, the preliminary evaluation of the storage technical performance indicators identified a relatively low injectivity, requiring a relatively large number of injector wells. Containment risks have also been flagged, such as the presence of faults, fracture corridors and a considerable number of existing wells. These risks will be evaluated further in subsequent project phases so that appropriate prevention and mitigation actions are taken.

A preliminary analysis of the critical risks associated with technical hazards was conducted to identify the major concerns regarding the two candidate storage sites. The critical hazards identified are presented in Table 7-1.

Table 7-1 Critical Hazards Relating to CO2 Storage

Element Hazard Main Performance Factor impacted
Reservoir Insufficient lateral extent of pinch outs Containment
Caprock Unidentified conductive faults crossing caprock Containment
Caprock Unidentified fracture corridors crossing caprock Containment
Caprock Permeability under estimated Containment
Wells Existing P&A wells leaking Containment
Faults Unidentified faults within the reservoir not laterally transmissive Capacity, Injectivity
Faults Bounding fault not sealing vertically or laterally Containment
Reservoir Permeability lower than expected Injectivity
Reservoir Porosity lower than expected Capacity
Reservoir Plugging due to salting out around well Injectivity

Most of the critical hazards are related to the sites’ containment performance, with faults being a primary concern. The presence of a large number of existing wells within the lateral boundaries of the site has also been considered as a potential threat to the safety of the storage.

It should be noted that the criticality of the containment risks associated to these hazards is currently perceived as high due to the lack of data. A reduction in this criticality is expected at the end of the appraisal phase, once more data has been acquired and subsequent studies have been completed. As a result, a much better representation of the geological model and potential technical risks will be obtained. This includes a work program that encompasses storage site definition, geological and reservoir modelling, seismic data, and after obtaining the complete results from the laboratory work and associated analyses of samples from all wells on site. It is expected that further characterisation work, conducted during Phase 2 of the project (appraisal), will significantly reduce the uncertainties associated with many of the technical hazards currently considered as critical.

The same applies to hazards related to the reservoir properties (permeability, porosity, associated heterogeneities) for which estimates are based on data from neighbouring structures.

Possible prevention/mitigation measures have been identified and classified according to the categories: “site characterisation/appraisal”, “monitoring”, “site design” and “operational plan”.

Selected monitoring technologies, integrated in an overall monitoring plan will contribute to the prevention and mitigation of technical risks associated with the storage site.

The storage operational plan is composed of several elements, with associated risk prevention and mitigation measures:

  • Monitoring activities;
  • Maintenance activities: in accordance with the maintenance plan and the data obtained through wellbore monitoring (corrosion and cement logs), maintenance activities will be conducted on the injection infrastructure, and in particular on the injectors, in order to minimise the occurrence of associated risks. Workover operations, such as replacement of completion components, cement squeeze, acid treatment or even fracturing of the near wellbore area can all be considered in view of either preventing well integrity or injectivity risks or provide remediation measures when they have occurred.
  • The operational plan will actually contain the emergency response plan and all the remediation measures to be deployed and implemented in the case of occurrence of undesired events.