Sensitivity Analysis On Technical Parameters of Foam Assisted Water Alternating Gas (FAWAG) For Heavy and High Viscosity Oil Case

• Main Author: Farrastama Yoga, Hanif
• Format: Final Project
• Language: Indonesia
• Online Access: https://digilib.itb.ac.id/gdl/view/45304
• Institution: Institut Teknologi Bandung

The use of gas injection as an oil recovery method is challenging for heavy and high viscosity oil case. The great difference between gas and heavy oil density allows the occurrence of gravity segregation of the gas phase, and the high oil viscosity creates a greater viscous instability which results poor mobility ratio of the fluids. This increase the possibility of an early gas breakthrough, hence decreasing the effectivity of oil recovery. According to preceding studies, foaming surfactant has been used to improve the inherent poor mobility ratio of gas phase and liquid phase, therefore delaying the gas breakthrough and improving the volumetric sweep efficiency. FAWAG (Foam Assisted Water Alternating Gas) has been known as one of the foam injection methods, in which the gas and surfactant solutions are injected in separate slugs from a single well. FAWAG has been favored as a foam injection method due to the improvement in injectivity and the reduced risk of corrosion and material compatibility related risks. This study used CMG STARS to simulate the field scale application of FAWAG. The local-equilibrium ("foam interpolation") foam model in CMG STARS introduced a function FM, in which the effect of foam on gas mobility is represented as a modification of gas relative permeability. This study conducted sensitivity analysis on technical parameters of FAWAG, concerning the modeled foam quality, the duration of slug injections and tapered slug cases, and the surfactant and CO2 injection rates, as well as its feasibility on different reservoir permeabilities. This study also analyzed the impact of FAWAG in improving oil recovery and production performance in comparison to other EOR methods: water flooding, CO2 flooding, and WAG (Water Alternating Gas). The results proved that with oil recovery factor of 38.29%, the application of FAWAG significantly improved oil recovery; more than 10% gain of recovery factor in comparison to the former methods. The results also showed that FAWAG is only effective when applied on reservoir with high permeability; as for reservoir with permeability lower than 600 mD, FAWAG is not able to significantly improve oil recovery compared to WAG.