Evaluation of Miscible CO₂ Injection and Water-Alternating-CO₂ Injection for Enhanced Oil Recovery in an Algerian Triassic Reservoir

Why It Matters

The results guide operators on selecting CO₂‑EOR strategies that balance maximum oil recovery with enhanced sweep and long‑term carbon storage, influencing investment decisions in North African fields.

Key Takeaways

• Continuous miscible CO₂ injection yields 8.1% recovery factor.
• WA‑CO₂ injection reaches 7.9% recovery with better sweep efficiency.
• Reservoir pressure exceeds MMP by 54‑81%, favoring miscible flooding.
• WA‑CO₂ improves CO₂ retention, supporting long‑term storage.
• Study combines MMP screening, EOS modeling, and compositional simulation.

Pulse Analysis

Carbon dioxide flooding remains a cornerstone of enhanced oil recovery, offering both increased hydrocarbon extraction and a pathway for carbon capture and storage. In the context of Algeria’s prolific Triassic TAGI play, the reservoir’s high pressure—well above the minimum miscibility pressure (MMP) by up to 81%—creates an environment where CO₂ can dissolve fully into the oil, reducing viscosity and unlocking additional reserves. By applying the Peng‑Robinson equation of state, researchers accurately modeled fluid behavior, ensuring that the simulation reflects real‑world phase interactions critical for project planning.

The comparative analysis shows that continuous miscible CO₂ injection delivers the top recovery figure of 8.1%, confirming its effectiveness when the primary goal is to maximize output. However, the water‑alternating‑CO₂ (WA‑CO₂) scheme, with a 7.9% recovery, offers distinct operational advantages: it mitigates gas channeling, enhances sweep efficiency, and retains a larger fraction of CO₂ within the formation. These attributes are especially valuable for operators seeking to align oil production with carbon‑storage commitments, as retained CO₂ contributes to long‑term sequestration goals and can improve the economics of CCS‑linked projects.

For the broader industry, the study underscores the importance of tailoring EOR designs to reservoir characteristics and strategic objectives. While miscible CO₂ flooding is optimal for rapid, high‑volume recovery, WA‑CO₂ provides a balanced approach that supports both production and environmental stewardship. As North African basins continue to attract investment, integrating robust MMP screening, EOS‑based fluid characterization, and compositional simulation will be essential for de‑risking projects and delivering sustainable value. Operators can leverage these insights to negotiate better contracts, secure financing, and meet tightening ESG standards.