Evaluation of Mobility Control with Nanoparticle-Stabilized CO2 Foam

Abstract

Abstract CO2 foam has been used for different oil and gas applications such as hydraulic fracturing and enhanced oil recovery (EOR). Foam is used as a fracturing fluid to develop unconventional reservoirs and specifically water-sensitive reservoirs. It is also employed as an EOR fluid to control fluids mobility and improve sweep efficiency. Moreover, using foam as a hydraulic fracturing fluid provides rapid cleanup during flowback. Although it is common to use surfactants to generate and stabilize foams, they tend to degrade at high-temperatures (>212°F) and in high-salinity environments. Adding nanoparticles is a new technique to stabilize CO2 foams that supports the proppant-carrying requirements for fracturing fluids. The present work evaluates new foaming solutions that incorporate nanoparticles to investigate the mobility-control performance when these foams are used as hydraulic fracturing fluid. This study specifically investigates the effect of nanoparticles on the stability of alpha olefin sulfonate (AOS) foam and the corresponding mobility-reduction factor (MRF), which indicates the apparent fluid viscosity at high-temperature and high salinity. To achieve this objective, foamability and foam stability tests were conducted at 77 and 150°F. Foam stability was studied for various solutions using a high-pressure view chamber (HPVC) setup to find the optimal solution, at which higher foam stability in the CO2 foam system can be reached. Coreflood tests were also conducted on different Buff Berea sandstone cores at both 77 and 250°F. CO2 gas was injected with the different solutions simultaneously to generate foam with 80% quality. The pressure drop across the core was then measured to estimate the MRF. The results of this work show that foam half-life decreases as the temperature increases from 77 to 180°F. Nanoparticle-based foams are more stable over time compared to those stabilized by surfactant. AOS, as an anionic surfactant, improves the MRF by 300% compared to brine alone. Adding silica nanoparticles to the AOS solution improves the foam stability and increases the MRF eight-fold. At 250°F, the AOS solution retained foam stability, while the MRF increases to 28 compared to foam at room temperature. Surfactants may degrade at high temperatures, and hence, cannot be used to stabilize foam. Protecting surfactants from being degraded and improving the foam stability is of great importance and can be achieved by adding nanoparticles to the solution. Nanoparticle solutions can be used to improve CO2 foam stability. Adding nanoparticles is highly recommended for hydraulic fracturing applications, particularly in fracturing stimulation at high-temperatures.