Experimental assessment of pore fluid distribution and geomechanical changes in saline sandstone reservoirs during and after CO 2 injection
International Journal of Greenhouse Gas Control
A B S T R A C T Responsible CO 2 geosequestration requires a comprehensive assessment of the geomechanical integrity of saline reservoir formations during and after CO 2 injection. We assessed the geomechanical effects of CO 2 injection and post-injection aquifer recharge on weakly cemented, synthetic-sandstone (38% porosity) sample in the laboratory under dry and brine-saturated conditions, before and after subjecting the sample to variable pore pressure brine-CO 2 flow-through tests (∼170 h).
... ugh tests (∼170 h). We measured ultrasonic P-and S-wave velocities (V p, V s ) and attenuations, electrical resistivity and volumetric strain (ε v ). V s was found to be an excellent indicator of mechanical deformation during CO 2 injection; V p gives mechanical and pore fluid distribution information, allowing quantification of the individual contribution of both phenomena when combined with resistivity. Abrupt strain recovery during imbibition suggests that aquifer recharge after ceasing CO 2 injection might affect the geomechanical stability of the reservoir. Static and dynamic parameters indicate the sample experienced minor geomechanical changes during CO 2 exposure, with an increase of Δε v < 3% and a drop in ΔV s ∼1%. In contrast, due to brine-induced hydro-mechanical alteration, Δε v increased by ∼10% and ΔV s by ∼6%. This study provides a multiparameter, thermo-hydro-mechanical-chemical database needed to validate monitoring tools and simulators, for prediction of the geomechanical behaviour of CO 2 storage reservoirs.