1. Using standard data on the densities and molar volumes of minerals, what is the solid volume change (in percent solid
volume products/reactants) for the reaction Ca(OH)2 (portlandite) + CO2 = CaCO3 (calcite) + H2O? (In an open system,
with fluid flowing through open pores, the solid volume change might be similar to the total volume change).
2. How about the total volume change, including fluid with 100 ppmw ΣCO2 (the volume of dissolved CO2 in the fluid is
negligible). (In a closed system, the total volume change would be this second value).
3. In an elastic material, stress = elastic modulus x volumetric strain (%volume change ÷ 100). Assuming we are looking at
an open system where the solid volume change is close to the total volume change, and expansion is isotropic (the same
in all directions), use the shear modulus for portlandite (~ 20 GPa) to calculate the stress generated by this volume
change. How does this compare to the tensile strength of portlandite (~ 2 GPa)? Assuming some of the stress is tensional,
will the volume change fracture solid portlandite around growing calcite?
4. What are the solid volume change and total (closed system) volume changes for
2Fe (iron metal) + 6H2O(liquid) = 2Fe(OH)3 ferrihydrite + 3H2(gas)?
5. What is the relationship between hydraulic conductivity and permeability? What is the hydraulic conductivity for water
flowing through a porous sandstone composed of quartz with a permeability of 10-12 m2?
6. In lecture 10, we found that there is room for many years of CO2 storage at 5 Gt CO2/yr (~ 10% of current
annual global emissions) in depleted oil & gas reservoirs. This could potentially be useful, since such reservoirs
are already well-characterized, are known to have retained buoyant fluids (oil, gas) for 10’s to 100’s of millions of
years, and in some cases have already been permitted for CO2 injection for Enhanced Oil Recovery.
So let’s check that result in a different way.
Look at data on annual oil production at https://ourworldindata.org/grapher/oil-production-by
country?country=~OWID_WRL and annual gas production at https://ourworldindata.org/grapher/gas-production
Use these data and densities of oil
concentration_on_IFT_for_surfactant_flooding_optimization/figures?lo=1) and gas (convenient calculator at
https://www.unitrove.com/engineering/tools/gas/natural-gas-density) at 2 km depth in an area with surface
temperature of 15°C, a geothermal gradient of 25°C per km, and a hydrostatic pressure gradient.
What is the volume of pore space formerly occupied by all the oil and gas produced from 1965 to 2020?
7. Use the density of CO2 at the same conditions to calculate how many tons of CO2 can be stored in the volume
you found in (6) ? For how many years could this accommodate storage of 5 Gt CO2/yr ?