An Experimental Study of the Use of Silica and CNC Nanofluids for EOR by Spontaneous Imbibition
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Approximately half of the oil is still left in the reservoirs after primary and secondary oil recoverytoday. To increase the oil recovery from the reservoirs it is necessary to apply Enhanced OilRecovery (EOR) Methods. The EOR methods that are currently applied are often limitied by alow cost efficiency, thus new and more efficient methods has to be developed. This is why the useof nanofluids are being investigated for this purpose. In this report the use of nanofluids for EOR purposes is investigated through spontaneous imbibitionexperiments using Amott cells. Silica nanoparticles and cellulose nanocrystals (CNC) are used andcompared to using only low salinity water (LSW). The amount of oil produced from spontaneousimbibition experiments can be useful in predicting the oil recovery from a reservoir and thus toinvestigate the use of nanoparticles for EOR. Since all faces are open for imbibition in an Amott cellthe flow is considered counter-current. The contact angles and interfacial tensions between an oildrop and the different fluids applied are measured to identify the mechanisms causing the increasedoil recovery from adding nanoparticles. Since a high degree of aggregation of nanoparticles couldresult in permeability impairment and retention in a reservoir, the particle size distribution wasmeasured 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 oilrecovery of 33,37 %, compared to 27,09 % and 28,35 % for the LSW and the CNC nanofluid. Thismight be due to the silica s ability to change the wettability towards more water-wet. This abilitywas verified by the contact angle measurements which resulted in a contact angle of 29,68± for thesilica nanofluid, 60,06± for the CNC nanofluid and 68,57± for the LSW. The interfacial tension foran oil drop in suspension was lower for the LSW than for the silica nanofluid applied, this indicatesthat the lowering of interfacial tension is less important in terms of oil recovery than the wettabilitychange. A lot of oil was still stuck on the rock after fourteen days for the CNC nanofluid, thismight be due to the increased viscosity of the water. The relation between square root of timeand the oil recovery from the Amott test was not linear, this might be because the flow was notstrictly counter-current. Both the silica nanofluid and the CNC nanofluid showed little to no signof aggregation throughout the fourteen days, and they are thus considered stable within this time.