Enhancing Stability of Nitrogen Foam by PEG-Coated Silica Nanoparticles for Enhanced Oil Recovery Applications

After decades of extracting oil from Middle Eastern carbonate reservoirs, only around 30% of the initial oil in place has been produced, with the extraction of the remaining 70% reliant on enhanced oil recovery (EOR) methods. Foam-assisted gas injection serves as an effective technique for enhancing reservoir sweep efficiency. The use of nanoparticles (NPs) to stabilize foams has emerged as a promising area of research within petroleum engineering. This study methodically assesses and contrasts the impacts of stabilized Nitrogen (N2) foam─utilizing both bare and surface-coated silica (SiO2) NPs─on oil recovery performance from a limestone porous medium at various temperatures (28, 55, and 85 °C). The initial step involves modifying the surface of the SiO2–NPs. For this modification, SiO2–NPs were first treated with 3-methacryloxypropyltrimethoxysilane (MPS) as a coupling agent, followed by coating poly(ethylene glycol) (PEG) onto the MPS-modified surface. Subsequently, a solution of 0.06 wt % Sodium dodecyl sulfate (SDS) was prepared in a 0.5 wt % NaCl solution, then bare SiO2–NPs were added at concentrations ranging from 0.005 to 0.1 wt %. Nitrogen was injected into the suspensions at a flow rate of 50 mL/min, and the stability of the generated foam was assessed by measuring its half-lifetime. Foam stability reached its highest point at an SiO2–NPs concentration of 0.01 wt %, indicating the optimal NP content. Following the determination of the ideal concentration of SiO2–NPs, a comparison was made between the foam stability of bare SiO2–NPs and PEG-coated SiO2–NPs, with the most stable foam being utilized for flooding the limestone porous medium in EOR processes. The half-lifetime measurements of foams incorporating PEG-coated SiO2–NPs were, on average, eight times longer than the base foam at 28 °C and 6.5 times longer at 85 °C. The results indicated that PEG-coated SiO2–NPs exhibited the highest foam stability at all tested temperatures. Furthermore, at 85 °C, foams with bare SiO2 and PEG-coated SiO2–NPs enhanced the oil recovery from the limestone porous medium by 32 and 36%, respectively, which were 5 and 9% greater than foam flooding without the addition of NPs. These findings suggest that improved foam stability with PEG-coated SiO2–NPs results in enhanced oil recovery rates during foam flooding.