مطالعه شبيه سازي تأثير تزريق CO₂ به مخزن گاز ميعاني

This research presents a comprehensive study of the technical an‎d environmental feasibility of carbon dioxide (CO₂) injection as a strategy for enhanced gas recovery (EGR) an‎d carbon sequestration in condensate gas reservoirs. retrograde condensation presents a significant challenge in these systems, as the reservoir pressure dro‎pping below the dew point leads to the precipitation of heavy hydrocarbon fractions (C₁₀–C₁₅+) as an immobile liquid phase. This phenomenon, known as condensate banking, severely impairs the relative permeability of the gas an‎d traps high-value hydrocarbons, resulting in substantial economic losses. The study employs a high-resolution numerical simulation approach, utilizing CMG WinProp software for detailed fluid characterization an‎d CMG GEM software for 3D reservoir structure modeling. An 11-component fluid model, validated using laboratory data an‎d the Peng-Robinson equation of state (PR-EOS), was incorporated into a 9×9×4 grid system to eva‎luate three distinct operational scenarios over a 39-year period. These scenarios include natural depletion (Case 1) as a baseline, early CO2 injection (Case 2) initiated in 1986, an‎d late CO2 injection (Case 3) initiated in 2015 following significant depletion. Analysis of the results shows that the timing of CO2 injection is the primary determinant of final recovery efficiency. Early CO2 injection (Case 2) proved to be the optimal strategy, successfully maintaining reservoir pressure above the dew point of 3,000 psi for most of the simulation period. This proactive approach bypassed the downward regression zone, ensuring that heavy components remained in the highly mobile gas phase an‎d resulting in the highest recovery rates for both gas an‎d condensate. In contrast, the natural depletion baseline (Case 1) exhibited a rapid pressure dro‎p to approximately 600 psi, leading to severe condensate blockage an‎d a localized oil saturation of 19.7% near the wellbore wall. Furthermore, the study confirms the effectiveness of carbon dioxide as a remediating solvent in Case 3. Introducing carbon dioxide into a depleted reservoir resulted in a "rebound" in production rates through fluid swelling mechanisms, re-evaporation of captured fluids, an‎d a significant 40% reduction in oil viscosity. By reducing surface tension an‎d agitating previously immobilized condensates, Case 3 achieved a significant increase in fluid recovery compared to the baseline condition. Beyond hydrocarbon recovery, the research highlights the reservoirʹs environmental potential as a storage site. The model indicates that a substantial proportion of the injected carbon dioxide remains trapped, particularly in the highly permeable layers 1 an‎d 4. These findings support the adoption of carbon dioxide recycling as a sustainable management model that links increased energy production with global carbon neutrality goals through carbon capture, utilization, an‎d storage (CCUS). The study concludes that while early injection prevention is the optimal technical approach, late-stage carbon dioxide injection remains an effective tool for remediating mature gas condensate fields an‎d extending their economic viability.

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حميدرضا شاه وردي , محسن محمدي