CO2 Sequestration [Reservoir Thermodynamics]
1. With CO2 being highly compressible, how could we have a control over its thermodynamic properties (molar-volume, density, viscosity, specific heat, Joule-Thomson coefficient & sound speed) – that would dictate the resulting changes in CO2 velocity, static temperature, sound speed & Mach number - over aquifer space and time?
Feasible to capture the modulation of thermodynamic properties as a function of aquifer pore-geometry, upon CO2 injection?
2. When could we expect a smooth variation in thermodynamic properties (along the CO2 migration direction) – in the absence of choking conditions?
3. When and where could we expect, development of a shock wave, which characterizes infinitesimal discontinuity in thermodynamic properties – as a function of aquifer heterogeneity?
4. How fast super-critical CO2 would try to escape through the least-resistive pathways, which remain directly connected to the surface (say, through improperly abandoned wells) – for a given aquifer rock and fluid properties?
5. Whether the escape of scCO2 would try to generate a local-scale pressure depletion in the aquifer?
If so, would CO2 still maintain its energy state (isenthalpic condition)?
6. Under what circumstances, could we expect the phase-conversion of scCO2 to a sub-critical state (liquid or gaseous CO2) with consequent volume expansion?
How fast such phase conversion would be?
7. Following phase conversion as a function of aquifer pressure, temperature & density, to what extent, the pore-fluid, which was initially saturated with brine, would get filled with a mixture of super-critical, liquid or gaseous CO2 and brine?
How do we know the spatial and temporal distribution of 2-phase and 3-phase fluid conditions?
8. Can we assume that migrating CO2 would behave adiabatically with negligible changes in potential energy, towards estimating the total enthalpy of migrating CO2?
Whether the stagnation enthalpy would remain to be a conservative property?
Whether, the total enthalpy would linearly depend on the static (including internal energy of the flowing fluid in the absence of its kinetic energy) enthalpy?
OR
Could we expect CO2 to behave as an ideal gas, where stagnation enthalpy could be replaced with stagnation temperature; and static temperature could be related with isobaric heat capacity?
9. Can we assume that the migrating CO2 would reach a choking condition (where, Ma equals unity; and choked flow results when flow rates exceed sound speed)?
OR
Do we need to investigate the scenarios that trigger choking conditions in saline aquifers upon scCO2 injection – resulting from the variations in pressure and temperature of CO2 by wellbore processes including adiabatic heating, frictional loss and conductive heat exchange with surrounding rock material?
Suresh Kumar Govindarajan
Professor (HAG) IIT-Madras
https://home.iitm.ac.in/gskumar/
https://iitm.irins.org/profile/61643
26-July-2024
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