Extraction of the 1:1-scale well system





Status end June 2015: completion of overcoring at the Mont Terri underground Rock Laboratory

 Sketch of overcoring operations (not to scale)


The 1:1-scale well system, which was installed in the underground rock laboratory of Mont Terri, Switzerland, back in October 2012 by the ULTimateCO2 project, has now been extracted from its in-situ environment by overcore drilling. These overcoring operations were supervised by Swisstopo, partner in ULTimateCO2. ULTimateCO2 would like to acknowledge Obayashi, Japanese partner of the Mont Terri Consortium, who co-funded the overcoring together with Swisstopo.  

This final stage of the borehole experiment, the first of its kind in the domain of CO2 geological storage, will enable detailed laboratory study of the solid samples recovered, namely the well components (steel casing and cement) and the surrounding clay rock. It is a unique opportunity to study in detail, and under real conditions in terms of scale and materials, the effect that CO2 could have on the sealing properties of well equipment and the surrounding rock.



                            Figure 1: Sketch of overcoring operations (not to scale)

    overcoring operations lifting of the well-system

Figure 2: Retrieval of the well-system: overcoring operations        Figure 3: Retrieval of the well-system: lifting of the well-system


These laboratory results will complement previous in-situ studies carried out over more than two years since the experimentation was started in February 2013. Experiments have already been conducted to characterize both i) the evolution of well integrity (status of connections between the component parts) and ii) the effects that geochemical processes may have at the clay / cement / steel interfaces under various conditions, namely temperature and pressure, but also the geochemical environment. The borehole was first studied under its initial geochemical conditions, and later in an acidic environment with water containing dissolved CO2. 


 Sampling operations

                                                   Figure 4: Sampling operations

The results will help better understand the processes involved when a well is subjected to physico-chemical changes that could occur during its lifetime and, in particular, to a CO2-bearing environment. In a larger context, that of a CO2 storage site intersected by wells where these can represent potential leakage pathways for the stored CO2, this work will increase our knowledge on well behaviour and sealing, and thus contribute to ensuring the safety of geologically stored CO2 in the long term.

Learn more (see also the Publications page):

Dernière mise à jour le 12.08.2015