Perpustakaan Digital ITB

CO2-enhanced oil recovery (CO2-EOR) is fundamentally limited by the unfavorable mobility ratio between CO2 and reservoir oil, causing viscous fingering, gravity override, and poor sweep efficiency in reservoirs with strong vertical permeability contrast. Foam-assisted water-alternating-gas (FAWAG) addresses this by generating in-situ foam that raises CO2 apparent viscosity beyond conventional water-alternating-gas (WAG), yet field foam strength is typically calibrated from laboratory data and may deviate once applied at reservoir conditions. This study evaluates FAWAG performance for CO2 mobility control through numerical simulation in CMG STARS on a synthetic layered reservoir model, comparing it against continuous CO2 injection and WAG on an equivalent injection basis and further examining its sensitivity to foam strength by scaling the calibrated apparent viscosity from 0.1x to 2.0x. FAWAG achieved the highest oil recovery and lowest gas production among the three strategies, with gas breakthrough occurring gradually rather than sharply as under continuous CO2 and WAG. Its advantage over WAG in oil recovery and gas-oil ratio control persisted across the entire foam strength range, whereas a threshold was identified below which FAWAG no longer outperformed WAG in sweep efficiency, and CO2 utilization deteriorated at both strength extremes. These findings indicate that foam strength must be deliberately designed and validated against target reservoir conditions rather than adopted directly from literature calibration.