Research Info

Miscibility gas injection is a key method for enhancing oil recovery from reservoirs. In nanopores, where pore radii are reduced to the nanometer scale, confined liquids exhibit altered physicochemical properties, impacting vapor-liquid equilibrium calculations. This study employs a modified Peng-Robinson equation of state (PR-EOS) to model vapor-liquid equilibrium in both bulk and nanopore conditions, incorporating the effects of capillary pressure, temperature, and critical property shifts. The Parachor model is used concurrently to predict interfacial tensions (IFTs). The effects of enriched gas injection, including liquefied petroleum gas (LPG), natural gas liquids (NGL), and naphtha, on minimum miscibility pressure (MMP) and IFT were investigated. Results show that increasing LPG injection pressure from 0 to 25.28 MPa reduces IFT by approximately 83% in bulk (from 12.12 to 2.02 mN/m) and 92% in nanopores (from 8.81 to 0.67 mN/m) at a gas-to-liquid ratio (GLR) of 1.25 MSCF/STB. Similarly, NGL injection from 0 to 27 MPa decreases IFT by 83% in bulk and matrix states (from 12 to 2 mN/m) and 90% in nanopores (from 8.8 to 0.88 mN/m). For naphtha injection at pressures below 12 MPa, IFT decreases uniformly across all states, while above 12 MPa, IFT variations are observed with different GLRs, with reductions up to 87% in nanopores (from 8.25 to 1.07 mN/m) at 15.24 MPa. These findings highlight the significant reduction in IFT and MMP in nanopores, enhancing miscibility and improving EOR efficiency in tight and shale formations.