dc.description.abstract | Approximately half of the oil is still left in the reservoirs after primary and secondary oil recovery
today. To increase the oil recovery from the reservoirs it is necessary to apply Enhanced Oil
Recovery (EOR) Methods. The EOR methods that are currently applied are often limitied by a
low cost efficiency, thus new and more efficient methods has to be developed. This is why the use
of nanofluids are being investigated for this purpose.
In this report the use of nanofluids for EOR purposes is investigated through spontaneous imbibition
experiments using Amott cells. Silica nanoparticles and cellulose nanocrystals (CNC) are used and
compared to using only low salinity water (LSW). The amount of oil produced from spontaneous
imbibition experiments can be useful in predicting the oil recovery from a reservoir and thus to
investigate the use of nanoparticles for EOR. Since all faces are open for imbibition in an Amott cell
the flow is considered counter-current. The contact angles and interfacial tensions between an oil
drop and the different fluids applied are measured to identify the mechanisms causing the increased
oil recovery from adding nanoparticles. Since a high degree of aggregation of nanoparticles could
result in permeability impairment and retention in a reservoir, the particle size distribution was
measured in the nanofluid before and after the Amott test.
The use of silica nanoparticles in this experiment led to the highest oil recovery, with an average oil
recovery of 33,37 %, compared to 27,09 % and 28,35 % for the LSW and the CNC nanofluid. This
might be due to the silica s ability to change the wettability towards more water-wet. This ability
was verified by the contact angle measurements which resulted in a contact angle of 29,68± for the
silica nanofluid, 60,06± for the CNC nanofluid and 68,57± for the LSW. The interfacial tension for
an oil drop in suspension was lower for the LSW than for the silica nanofluid applied, this indicates
that the lowering of interfacial tension is less important in terms of oil recovery than the wettability
change. A lot of oil was still stuck on the rock after fourteen days for the CNC nanofluid, this
might be due to the increased viscosity of the water. The relation between square root of time
and the oil recovery from the Amott test was not linear, this might be because the flow was not
strictly counter-current. Both the silica nanofluid and the CNC nanofluid showed little to no sign
of aggregation throughout the fourteen days, and they are thus considered stable within this time. | en |