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Wettability Alteration in Low-Permeability Sandstone Reservoirs by “SiO2–Rhamnolipid” Nanofluid
journal contribution
posted on 2019-12-03, 15:25 authored by Di Wang, Shanshan Sun, Kai Cui, Hailan Li, Yejing Gong, Jirui Hou, Zhongzhi ZhangThe wettability condition of a rock’s surface
is an enormous
parameter for enhanced oil recovery (EOR) in low-permeability reservoirs.
It determines the spreading of injected water and the adhesion of
residual oil on rock surfaces. In this study, a new nanofluid composed
of silica nanoparticles and rhamnolipid in brine was utilized as an
effective agent to alter the wettability of a rock’s surface.
In order to obtain rock surfaces with different initial wettabilities,
hexamethyldisilazane (HMDS) was used for the sample preparation. The
measurement of three-phase contact angles for water/air/rock and brine/oil/rock
were performed to explore the contact situation between a rock surface
and movable fluids, and the spontaneous imbibition test researched
the process of oil recovery with nanofluid. By evaluating the experimental
measurements, nanofluid showed a significant potential in wettability
alteration from oil-wet toward water-wet state, which is an important
mechanism for “scraping” oil drops from a rock surface
during nano-EOR process. Moreover, a total of nine coreflooding tests
were performed to investigate the effects of rock wettability on waterflooding
and nanofluid flooding, respectively. The results revealed that an
intermediate-wet state of a rock’s surface is in favor of the
oil recovery especially for waterflooding, and nanofluid, resulting
in an additional 5.3–6.8% increments in oil recovery compared
to conventional waterflooding. In conclusion, nanofluids show a significant
potential for EOR from low-permeability cores, implying a wide application
in oil fields.