Nanoparticle-Stabilized Strong Foam for EOR in Fractured Reservoirs

Abstract Many carbonate reservoirs are fractured. Injection of EOR agents (miscible gases or surfactant solutions) into fractured reservoirs leads to flow through the fractures and bypassing of the matrix. These fluids can be directed into the matrix if the fluids are injected into the fractures as a foam. The goal of this work is to develop a strong foam for injection into fractured reservoirs by using nanoparticles. Ethyl cellulose nanoparticles (ECNP) were prepared from ethyl cellulose with 48% ethoxy groups. ECNP were used to stabilize foam with and without a nonionic surfactant, CH3-70PO-100EOH. The size of the ECNP prepared was smaller than 200 nm with a narrow size distribution. The addition of ECNP to a nonionic methoxy surfactant (CH3O-70PO-100EOH) helped with foamability and foam stability compared to surfactant only samples. The foam stability in the presence of oil was also improved by ECNP. Foam flooding with an oil-wet fractured Texas Cream limestone indicated that the oil recovery was much higher with ECNP/nonionic surfactant compared to a conventional AOS foam and also the immiscible gas (methane/ethane gas mixture at a molar ratio of 1:1) alone. The oil recovery was 71% with the injection of 80% quality foam using 500 ppm ECNP and 1.5 wt% nonionic surfactant at 1wt% NaCl concentration. This work illustrates that the oil recovery can be improved with a strong foam even with gases that are not multi-contact miscible.