Activity: Talk or presentation › Talk or presentation at a conference
Recently we have reported an experimental study comparing immiscible gas, water-alternating-gas (WAG) and foam-assisted chemical flooding (FACF) for enhanced oil recovery. We found that oil recovery by FACF is much higher compared to the other gas injection schemes studied, essentially due to the drastic reduction of oil – water interfacial tension (IFT) and good mobility control provided by foam. This paper aims to test and validate proposed mechanisms for the high recovery factor due to FACF, and WAG, by conducting dedicated numerical simulations and by matching numerical simulation results to experimental observations.
1D simulations were conducted using UTCHEM. This comprehensive in-house three-dimensional numerical simulator captures the main features of chemical flooding (geochemistry, phase behaviour, etc.) as well as their coupling with multi-phase flow. CT scan data were used to build models with accurate digital representation of the rock (porosity and permeability). The FACF corefloods were modelled by including the surfactant phase behaviour as a function of salinity, fluid rheology, capillary desaturation of oil, gas mobility reduction to due foam generation, and potential essential geochemical reactions that occurred in the sandstone core.
Relative permeability curves for the primary drainage and water flooding injection stages were determined using the measured saturation distributions by CT scanning in combination with effective permeability mea- surements based on sectional pressure drops over the core length. History matching WAG injection revealed that gas relative permeability diminished as a function of increasing WAG cycles, which is consistent with gas trapping. Oil mobilization due to injection of a surfactant slug in the FACF experiments, was properly modelled at the two salinity conditions studied. It required successful simulation of the surfactant phase be- haviour and obtaining representative relative permeability curves for low IFT flooding. Numerical modelling of drive foam injection, using an alternative local equilibrium approach, resulted in successfully reproducing laboratory observations.
Three-phase diagrams, constructed based on both experimental and numerical modelling results, revealed for the first time which phenomena are dominant for the EOR processes studied. In particular, the proposed mech- anism for oil bank formation and its subsequent displacement by foam during FACF was clearly established.