Abstract
Several gas Enhanced Oil Recovery (EOR) pilots enhanced with aqueous-foam based conformance solutions have been implemented in the last 30 years. While these pilots were technically successful, there were economic challenges limiting their commercial viability. Many of these pilots were implemented with water-soluble foaming surfactants that can get adversely affected by near wellbore gas-water gravity segregation and adsorption loss up to 90% of the injected surfactant. Novel, gas-soluble surfactants can be injected with the gas phase where these surfactants are carried with the gas to thief zones faster and deeper with relatively lower adsorption to the rock surface. However, the conventional foam modeling approach relied only on the surfactant concentration in brine to determine foam strength, which adversely predicted the performance of gas soluble surfactants. With proven laboratory evaluations and multiple successful field implementations, the advantages of low adsorbing and gas soluble surfactants cannot be ignored. In this paper, the advantages of surfactant partitioning to the gas phase are confirmed by correcting the conventional foam modeling approach while simulating 1D transport of CO2-foam displacing brine in porous media.
An empirical foam model was developed from the lab scale core flooding work of CO2foam transport through porous media using a novel gas-soluble foaming surfactant. While investigating the performance of gas soluble surfactants, global surfactant concentration was used to determine foam strength as the surfactant can transport to the gas-water interface from both the phases. Lab experiments and simulations with an improved foam modeling approach confirmed that a higher gas phase partitioning surfactant generated robust foam and deeper foam propagation while injecting surfactant with CO2in a water saturated core. In addition, comparing three partition coefficient scenarios around 1 on mass basis, the higher gas phase partitioning surfactant showed the larger delay in gas breakthrough. Overall, the simulation results with our better modeling approach do support the advantages of the higher gas phase surfactant partitioning in deeper foam transport and conformance enhancement for the gas-EOR technology.
The influence of solution chemistry on air-water interfacial adsorption and transport of PFOA in unsaturated porous media
