Application of Multi‐Criteria Decision Analysis (TOPSIS) for Screening Enhanced Oil Recovery Methods: A Case Study of Iraqi Reservoirs

ABSTRACT Oil production worldwide is declining, and many reservoirs are approaching maturity; therefore, enhanced oil recovery (EOR) is important to field performance. EOR is important for the continuing power of petroleum basins and national energy security. Choosing an appropriate EOR process, however, remains complicated because of the heterogeneous nature of reservoir conditions and the multi‐criteria decision. It means that this study employs TOPSIS as a screening tool. TOPSIS is a method that assists decision‐makers. Nine reservoir and fluid properties—API gravity, oil saturation, formation type, net thickness, viscosity, permeability, temperature, porosity, and depth—were used to evaluate 16 candidate EOR methods, including miscible/immiscible gas injection, chemical flooding, and thermal processes. The algorithm was applied manually to 12 Iraqi reservoirs covering a wide range of lithologies and conditions. Results show that surfactant + polymer/alkaline (P/A) is the most favorable method overall, accounting for 50% of the top rankings, particularly in reservoirs with moderate API gravity and relatively low viscosity. Immiscible CO 2 ranked second (25%), followed by immiscible N 2 (16.7%) and miscible N 2 (8.3%), while steam injection was consistently the least suitable under the studied conditions. An example from the Baba field demonstrates the full TOPSIS procedure, in which surfactant + P/A achieved the highest closeness coefficient (Ci = 0.634). These findings highlight the usefulness of TOPSIS as a reproducible and objective decision‐making framework for selecting EOR methods in Iraqi oil reservoirs.