Study On Sheet Carbon-based Nano-Oil Displacement Materials

After oilfield water flooding and conventional enhanced oil recovery technologies,50%or more of the crude oil remains underground,which is difficult to effectively extract.New technologies that further greatly increase the recovery rate need to be studied.Nano flooding can be regarded as a strategic replacement technology for conventional chemical flooding due to its special properties such as emulsifying crude oil and wetting reversal.The flaky nano-oildisplacing agent has a large specific surface area and surface energy,significantly reduces the oil-water interfacial tension,increases the contact angle between the oil and the rock formation,and makes the crude oil easier to recover.Studies have shown that sheet-like nanomaterials have great potential to improve oil recovery.In the first part of this article,by comparing the existing synthesis methods,on the basis of the successful synthesis of one-sided modified graphene oxide,the yield of the synthesis method is improved and the experimental procedure is simplified.Design and synthesize asymmetric modified graphene oxide S-GO-O.The second part is to test the dispersion stability of two sheet-like nanomaterials,and select S-GO-O nanofluid as the main body to screen the dispersion stabilizer.The dispersion stabilizer that can improve the temperature and salt resistance of S-GO-O nanofluid is selected from the surfactants commonly used in oilfields and polymer materials commonly used in laboratories.In the third part,the optimal injection concentration of S-GO-O is determined by homogeneous cores with different injection concentrations and different permeability.On this basis,after eliminating the influence of dispersion stabilizers,a displacement experiment of heterogeneous cores is carried out.To explore the applicability of S-GO-O nanofluids in heterogeneous layers.Finally,based on the oil displacement effect obtained by S-GO-O,a micro displacement experiment was carried out,combined with the characterization and performance test of S-GO-O,to explain the oil displacement mechanism of S-GO-O nanofluid.The experimental results show that compared with GO-O,S-GO-O nanofluid exhibits excellent amphiphilic properties.The grafting of hydrophilic groups also makes S-GO-O have better stability.In the high-temperature and high-salt oil reservoir environment,S-GO-O nanofluids with a concentration of 100 mg·L-1 have shown excellent oil recovery capabilities in homogeneous core flooding experiments with different permeability.In the homogeneous core flooding experiment with a permeability of 350 m D,the recovery rate was increased by18.8%.After eliminating the influence of dispersion stabilizers,S-GO-O nanofluid in the threelayer heterogeneous core flooding experiment increased the recovery rate by 11.6%.The S-GOO nanofluid with a concentration of 100 mg·L-1 changed the oil-wet core surface to neutral wettability.Combined with the characterization of S-GO-O and basic performance testing,it is found that S-GO-O can spontaneously accumulate on the oil-water interface,and S-GO-O nanosheets have the ability to change the wettability of the reservoir surface.The single-sided sulfonic acid group can better help the nanosheets to migrate in the water,reduce formation loss,expand the sweep coefficient,and improve oil recovery.