CO2 Sequestrated Enhanced Oil Recovery
1. MMP refers to the pressure @ which the injected CO2 and the initial oil in place become multi-contact miscible and eventually, the displacement process becoming very efficient. And, if the injection pressure is too low, the displacement would still be 2-phase immiscible, and respective local displacement efficiency would be below the desired level. However, if the pressure is too high, then, although the displacement would become multi-contact miscible, and the oil recovery could reach the desired level, the cost of pressurizing the injected CO2 would remain to be larger than necessary, and thereby the concept of MMP becoming sensitive/critical.
Albeit its importance @ laboratory-scale, does the concept of ‘Minimum Miscibility Pressure’ (MMP) occur in a real field scenario?
2. At the field-scale, whether MME (Minimum Miscibility Enrichment representing the enrichment level of a particular or group of components in a multi-component CO2 injection for a given displacement pressure that causes the displacement to become multi-contact miscible – as a function of varying injected CO2 gas composition) deserve special attention, on top of following MMP (as a function of varying pressure to achieve miscibility)?
3. Co2 Sequestrated EOR: How easy would it remain to capture the field-scale details that involves the physical and chemical processes, where, the injected CO2 gets mixed with the original oil in place and eventually, co2 and oil forming a single mobile phase through repeated/multiple contacts (wherever the injected CO2 penetrates the formation) upon meeting favorable reservoir conditions?
4. Feasible to capture the field-scale details on the coupled effect of reservoir heterogeneity, viscous fingering and gravity segregation that essentially limit the fraction of the reservoir swept by the injected CO2?
5. What is the physical significance and field-scale relevance of representing the displacement process as a one-dimensional, two-phase and dispersion-free flow, where, the displacement becomes piston-like, and eventually, the oil recovery becoming 100% @ 1 pore volume of CO2 injected @ MMP?
6. Does the laboratory-scale determination of MMP for a miscible CO2 injection involve the trade-off between achieving high oil recovery and mitigating the production costs?
7. What is the physical significance of defining MMP as the minimum recovery level for a given co2 injection amount and the bend in the curve of recovery (point of maximum curvature that occur near the intersection of the extrapolated asymptotes of the low-recovery and high-recovery regions; and MMP referring to the pressure @ which the recovery curve levels off) plotted against pressure?
8. Although slim tube tests towards measuring MMP remains to be expensive and time-consuming, can rising bubble experiments be used to forecast MMP for condensing/vaporizing CO2 drives?
9. Is there a comprehensive MMP correlation that predicts MMPs systematically for arbitrary oil and gas mixtures (as MMP correlations remain to have different forms depending on whether they are for CO2, CH4, N2 or a gas mixture)?
10. How precise would be the extrapolation of the recovery curve to dispersion-free limit towards getting rid-off numerical dispersion effects (as numerical dispersion smears out the composition fronts, and thereby making the numerically calculated oil recovery to remain to be inaccurate for MMP calculations)?
11. Why does mixing-cell approach provide better forecast towards predicting MMPs for condensing/vaporizing gas drives than using the single-cell version?
12. To what extent a mathematical model describing the determination of MMP, conceptualized as a Riemann problem by assuming the complete absence of diffusive and dispersive effects – would reflect the real field-scale scenario?
In such cases, how precise would the estimation of MMPs deduced from the geometry of key tie lines and critical locus upon developing multiple-contact miscibility?
Dr Suresh Kumar Govindarajan
Professor [HAG]
Petroleum Engineering
IIT Madras
11-Jan-2025
Addressing the Mixing-Cell and Single-Cell Approach in Predicting MMPs
The mixing-cell approach is often preferred over the single-cell approach for predicting Minimum Miscibility Pressures (MMPs) in condensing/vaporizing gas drives because it better accounts for the multi-stage, dynamic interactions between the injected gas and the reservoir oil. Below are the key reasons for its superiority:
Field-Scale Relevance of MMP and Multi-Contact Miscibility
Laboratory and Field Modeling Challenges
Summary
The mixing-cell approach provides a better forecast for MMPs because it models the dynamic, multi-contact interactions between gas and oil more realistically, capturing the essence of miscibility development in condensing/vaporizing drives. While it simplifies field-scale phenomena, it is a more reliable predictor compared to the single-cell approach. For field applications, integrating MMP predictions with advanced reservoir simulations that account for heterogeneity and coupled physical processes is essential for optimal CO₂ EOR design.
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