CO2 Sequestrated EOR
1. If dissolution of CO2 expands the volume of crude oil, then, would it increase the energy of elasticity of the reservoir formation?
And, in turn, would it increase the internal kinetic energy of crude oil?
If volume expansion increases the internal kinetic energy of crude oil, then, would it, in turn, reduce the capillary resistance and reduce the flow resistance in the process of crude oil flow?
And, subsequently, would it improve the flow capacity of crude oil?
2. When CO2 gets dissolved in crude oil, whether, the viscosity of crude oil would decrease significantly?
If so, then, does this reduction in crude-oil viscosity depend on pressure and temperature of the reservoir?
Does this reduction in crude-oil viscosity also depend on viscosity of the non-carbonated crude-oil?
Would it effectively expand the swept area of crude oil?
And in turn, would it improve the mobility ratio of crude oil?
As a result, whether, the flow of the crude oil would remain to be improved?
In turn, would it improve the efficiency of oil displacement?
Dr Suresh Kumar Govindarajan Professor [HAG]
IIT–Madras 04-March-2025
Yes, the dissolution of CO₂ in crude oil can increase the energy of elasticity (also referred to as elastic energy storage) of the reservoir formation, but the extent depends on several key factors.
How CO₂ Dissolution Affects Elastic Energy of the Reservoir Formation
1. Volume Expansion of Crude Oil:
o When CO₂ dissolves in crude oil, it reduces the oil viscosity and increases its volume (oil swelling).
o This expansion leads to increased pore pressure within the rock formation, potentially reducing the effective stress on the rock matrix.
2. Impact on Elastic Energy Storage:
o Reservoir Pressure Increase: The expansion of crude oil due to CO₂ dissolution increases pore pressure, which can store additional elastic energy in the rock formation.
o Reduced Effective Stress: If the pore pressure rises significantly, it reduces the effective confining stress (σ' = σ - Pp), which may decrease the rock’s stiffness and elasticity. However, if the rock is already under high stress, the overall deformation may still allow for increased elastic energy storage.
o Compaction and Rock Integrity: If the increased pore pressure remains within the rock’s elastic limit, the formation will behave elastically and store more energy. However, if it exceeds the yield strength of the rock, plastic deformation or fracturing could occur, dissipating energy rather than storing it elastically.
Considerations in Energy Storage and Elasticity
• Rock Type: Carbonate formations and sandstones respond differently. Highly compressible formations may exhibit more elastic energy storage due to CO₂-induced pore pressure increases.
• Pore Fluid Interactions: The interaction between CO₂, crude oil, and formation water alters the wettability and capillary forces, influencing the overall stress distribution and elasticity.
• CO₂ Concentration & Saturation: Higher CO₂ dissolution may lead to greater expansion, increasing the stored elastic energy up to a certain threshold before inducing structural instability.
Conclusion
Yes, the dissolution of CO₂ in crude oil can enhance the elastic energy of the reservoir formation by increasing pore pressure and inducing oil expansion. However, if the pressure increase is too high, it could lead to plastic deformation or even fracturing, which would dissipate stored elastic energy instead of enhancing it. The overall impact depends on the rock’s mechanical properties, fluid interactions, and pressure conditions.
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