Improved Oil Recovery in Fractured Reservoirs by Strong Foams Stabilized by Nanoparticles

Abstract

Enhanced oil recovery in fractured reservoirs is challenging because injected fluids flow mainly through the fractures without displacing oil from the matrix. Foam can enable injection into the matrix by creating a high pressure in the fractures. However, the foam has to be strong and stable in the presence of oil recovered from the matrix. This study focuses on developing a strong foam using nanoparticles and surfactants. Ethyl cellulose nanoparticles (ECNP) with a relatively narrow size distribution were prepared and dispersed in brine along with a nonionic surfactant (SF). The SF performed as both a nanoparticle dispersion agent and a foaming agent. The foam by ECNP/SF had better foamability and stability than the SF foam in the presence of oil. The mobility reduction factor of the ECNP/SF foam was 100 times larger than that of the SF foam and 3 times larger than an alpha olefin sulfonate (AOS) foam in a sand pack. Foam was injected into a fractured oil-wet Texas Cream limestone core saturated with oil. The oil recovery due to the ECNP/SF foam was significantly higher than those with only gas injection and conventional AOS foam injection. The novelty in this work lies in combining nanoparticles with surfactants to generate a strong foam which can be used to improve oil recovery from fractured, oil-wet reservoirs.