Optimization of Foam Performance to Improve CO2 Flooding Efficiency in Tight Reservoirs: A Numerical and Sensitivity Analysis Study

Abstract

Foam-assisted CO2 flooding is a promising enhanced oil recovery (EOR) technique designed to mitigate the poor conformance and early gas breakthrough that limit conventional gas injection in tight reservoirs. While effective, the process is highly sensitive to foam quality (FQ), an operational parameter that has not been systematically optimized for tight formations. This study establishes a definitive optimization of foam quality (50–90% CO2 fraction) by integrating advanced numerical simulation with proxy-based sensitivity analysis. Using CMG-GEM for compositional simulation and CMOST for uncertainty analysis, this work demonstrates that foam-assisted CO2 flooding is the superior recovery method, achieving an ultimate recovery of 85.3% OOIP. This significantly outperforms Water-Alternating-Gas (WAG) injection (76.2%) and continuous CO2 flooding (65.7%). A precise operational optimum was identified at 70% foam quality, which uniquely balances foam strength for mobility control with deep propagation capability. This optimal formulation maximizes sweep efficiency, drastically reduces the gas-oil ratio (GOR), and maintains a near-zero water cut. Crucially, a global sensitivity analysis (Sobol method) reveals that this optimum is also the most robust for field application. The 70% foam quality scenario presents a balanced, manageable parameter regime where recovery is governed jointly by horizontal permeability (49%) and initial reservoir pressure (33%). In contrast, an 80% foam quality shifts to a high-uncertainty, permeability-dominated regime (82%), making the recovery outcome highly unpredictable. This research provides a practical, simulation-validated framework for designing efficient and reliable foam floods, offering a clear pathway to unlock substantial incremental recovery from challenging tight reservoirs worldwide.