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Δευτέρα, 29 Οκτωβρίου 2018

State-of-the-Art review of CO2 Storage Site Selection and Characterisation Methods


Storage capacity pyramid for saline aquifers (modified after Bachu, 2003).

Estimated CO 2-ECBMR potential of EU GeoCapacity & GESTCO countries-after Wójcicki et al. (2007)

Buoyancy forces acting on the crest of the structural closure (after the CO2STORE manual Chadwick et al., 2006)
Carbon dioxide Capture and Storage (CCS) is a technology that could contribute significantly to reduced CO2 emissions to the atmosphere. By capturing carbon dioxide emitted from industrial processes, compressing it and injecting the CO2 into underground geological reservoirs of porous rock for permanent storage, it provides a bridging solution to mitigate the climate change while renewable energy sources and other low carbon industrial technologies are developed to large-scale implementation.

The selection and characterisation of potential CO2 storage sites are essential steps in progressing a CCS project. The site selection process should demonstrate that the site has sufficient capacity to store the expected CO2 volume and sufficient injectivity for the expected rate of CO2 capture and supply. The integrity of the site has to be assessed for the period of time required by the regulatory authority, so as  avoid any unacceptable risks to the environment, hum an health or other uses of the subsurface.

The main objective of this report is to identify and review site selection and characterisation methods. This report presents and discusses all the steps required to assess the capacity, performance and integrity of a site.

Simulation of CO2 storage in an underground formation requires a complex multi-disciplinary effort,
with the analysis of a number of interacting processes, including geology, multi-phase flow and transport, geochemistry and geomechanics.

A site characterisation first calls for the geological characterisation and  modelling of the site at basin and reservoir scales and the modelling of flow and transport mechanisms so  as to simulate the short-term to mid-term behaviour of the storage.

As well as hydrodynamic effects,  geomechanical effects generated by the injection of a large volume of fluid in the subsurface have to be  modelled over a long period. Modelling geochemical and biological processes is essential to understand  the geochemical feedback on the reservoir properties and the trapping mechanisms that will occur.

All these skills and knowledge are required to assess potential environmental impacts and risks. The estimation of the economical viability of the project is also essential to decide whether a geologically suitable storage site can actually be developed for CCS.

In parallel with the technical aspect of characterising the site, public perception and acceptance appears to be a potential major impediment to deployment of CCS and so social activities towards local communities have to be performed at a very early stage.