Experimental investigation of nanofluid enhanced oil recovery by spontaneous imbibition

Nanofluids have been recently proposed as new chemical agents for enhanced oil recovery. In this study, in order to reflect the effect of nanofluids on imbibition, the imbibition performance of manganese chloride (MnCl(2)) solution, sodium dodecylbenzene sulfonate (SDBS) solution, and silica (SiO(2)) nanofluids were studied by a spontaneous imbibition experiment at 25 °C and 0 MPa. The oil production from pores with different sizes and the imbibition efficiency were tested by nuclear magnetic resonance T(2) spectroscopy and metering in spontaneous imbibition. In addition, the interfacial tensions between the imbibition liquids and oil were tested. The changes in the contact angle of the core slice before and after immersing in imbibition liquids were measured. The silica nanofluid is used as the imbibition liquid, and the shift of the T(2) spectral peak to the left is not obvious and shifted by only 23.95–25.72 ms, the change in the contact angle is 6.63°–12°, the interfacial tension between the nanofluid and the simulated oil is 0.25–0.41 mN m(−1), and the imbibition efficiency was slightly improved with increasing nanoparticle concentration, up to 57.40%, which improved by 16.14% and 32.95%, respectively, compared to the surfactant solution and the manganese chloride solution. This shows that the silica nanofluid can effectively improve oil production in small pores, reduce oil–water interfacial tension, and change rock wettability.