CO2 Sequestration [Laboratory-Scale Investigation Vs Field-Scale Reality]

1. Feasible to capture the displacement of brine by the injected super-critical CO2 – in the presence of coupled viscous-fingering and gravity @ lab-scale?

2.  How precisely would be able to capture viscous fingering @ lab-scale as the viscosity ratio could generally exceed 20 with super-critical phase of CO2?

In the absence of favorable viscosity ratio, how could we justify the laboratory-scale measurements of

(a) capillary pressure – saturation curves; and

(b) relative permeability measurements?

3. How exactly to take into account, the laboratory-scale observations with reference to the concept of ‘field-scale geological heterogeneity’?

With ‘CO2 leakage monitoring’ becoming crucial in the long-run, whether, the concept of both scale-dependent and time-dependent heterogeneity (for example, space and time-dependent dispersivity) would remain to be critical @ field-scale (which has no relevance @ laboratory-scale)?

For that matter, even, capturing ‘capillary heterogeneity’ would remain to be feasible @ lab-scale?

4. Would it remain feasible to capture the onset of instability @ lab-scale {on top of the conventional measurements involving (a) @ end point saturation; and (b) @ shock front saturation}, where its consequence leads to a solution for the stability index becoming unbounded in the limit as IFT tending to zero?

How exactly to deduce the ‘right mobility ratio’ – pertaining to the saturation and its associated relative permeability values – that triggers the onset of viscous fingering?

5. In the context of CO2-brine interfaces flowing within a saturated subsurface aquifers/reservoirs, would it remain feasible to capture the following two instabilities @ lab-scale?

(a) Short wave-length instability (which addresses fingering @ pore-scale, and it remains associated with complex patterns of wettability variation; and requires the consideration of an ‘effective IFT’ that takes into account the enhancement in contact line length)

(b) Long wave-length instability (which addresses fingering @ Darcy-scale, where, the curvature is nearly on the same order of magnitude as the finger wave-length)

In particular, can we capture the way the capillary forces controls/suppresses the wave-length (width of the finger) @ Darcy-scale – using experimental investigations?

6. Unlike laboratory-scale observations, will we not have a clear separation of CO2 on the upstream and brine on the downstream @ field-scale scenario, when ‘pore-scale dimension’ remains to be much smaller than ‘finger wave-length’?

7. How could we capture the presence of saturation and its associated mobility-gradient behind the shock front (which remains as a part of rarefaction wave) @ lab-scale – that impacts the overall stability following onset?

Suresh Kumar Govindarajan

https://home.iitm.ac.in/gskumar/

https://iitm.irins.org/profile/61643