Leader: EPFL (Prof. Dr. Lyesse Laloui, Dr. Eleni Stavropoulou)

Participants: UniGe (Dr. Luca Guglielmetti, Dr. Antoine de Haller, Dr. Yasin Makhloufi, Prof. Dr. Andrea Moscariello)

The objectives of the work package are:

• Provide mineralogical, petrophysical and hydromechanical characterization of field cores.
• Evaluate the coupled geomechanical and geochemical response of basalt reservoir rocks to CO₂-rich seawater injection under realistic conditions.
• Quantify the time-dependent response of mineral trapping.

The WP will focus on the investigation of the coupled thermo-hydro-chemo-mechanical (THMC) response of the basaltic material upon injection of CO₂ dissolved in sea water. The evolution of the transport properties (permeability) will be characterized with hydromechanical testing under representative field conditions (pressure, temperature) and the assessed results will be associated to the evolution of the microstructural properties of the material that will be quantitatively characterized with 3D x-ray image analysis. Connected porosity is the most important property of the material for the evaluation of optimal storage and eventual reduction (clogging) can significantly limit the storage potential of the material. For injection under constant flow rate, clogging can lead to local increase of pore pressure, reduction of effective stress and triggering of micro-seismicity.

The proposed experimental testing campaign at both meso- and micro- scale aims to shed light on the coupled geomechanical and geochemical behavior of basalts upon CO₂-rich seawater injection. The objective of the meso-scale experiments (Task 4.1) is to investigate the evolution of mineralization un-der flow conditions. A series of basalt samples at the centimetric scale will be exposed to CO₂-rich seawater under different levels of pressure (P = 2-4 MPa) and temperature (T = 40-60◦C). The micro-scale experiments (Task 4.2) will be conducted on very small basaltic samples (d = h = 5 mm) with live x-ray tomography for the first time; the study of smaller size samples will enable significant spatial resolution (higher image resolution) improvement. Finally, the geochemical properties of the material and the injected fluid will be characterized (Task 4.3) and based on which the hydromechanical results will be further interpreted. The results of this WP4 will help the calibration of the field-scale static models in WP3 and aid in the interpretation of results in WP2.

Task 1
Hydromechanical testing
(EPFL, month 1-10)

Task 2
CO₂ exposure tests during in-situ x-ray tomography
(EPFL, month 4-16)

Task 3
Mineralogical and petrological characterization
(UniGe, month 5-8)