3.2.2 Adsorption inhibition

Polymer-coated nanoparticles were developed due to overcome the aggregation and

Rheology is defined as the study of flow and deformation behaviors of fluids under stress [76]. For EOR applications, an improved rheological behavior of injectant is required to inhibit viscous fingering phenomena and maintain a suitable mobility ratio in the reservoir; which requires that the displacing fluid maintain its viscosity and chemical integrity in the presence of resident reservoir brines [77]. Polymer and nanoparticles undergo degradation in the presence of reservoir brines. The cations present in the brine interact with the carboxylate and amide groups in the polymer molecule resulting in viscosity loss [78]. In the case of nanoparticles, the electrostatic attraction among nanoparticles are increased in the presence of brine fostering their aggregation and agglomeration; which implies the loss of surface functionality that is required for EOR [79]. However, the combination of polymer and nanoparticles results in a synergistic effect that improves the rheology

The preparation of polymer-nanoparticles blends involves the mixing of the nanoparticle and the polymer solution or grafting of the polymer on the nanoparticle [80, 81]. Subsequently, interactions occur between the nanoparticle and the carboxylate and amide group in the polymer molecules. Therefore, nanoparticles act as physical crosslinkers among the polymer chains forming three-dimensional network of stable flocs that increases the viscosity of the suspension [82]. At high temperature, polymer-nanoparticles blends exhibit better rheological performance due to the enhanced bridging induced flocculation [82, 83]. Furthermore, in the presence of reservoir brines, nanoparticles shield the polymer backbone from the cations of the brine by inducing ion-dipole interactions that inhibit the degradation

Lai et al. noted that the shear and mechanical resistance of acrylamide polymer solution can be increased by adding modified nano-SiO2, because the presence of SiO2-NP caused a reduction of the hydrodynamic radius of the polymer molecules [84]. Hu et al. studied the rheological properties on an oilfield polyacrylamide (HPAM) -SiO2 NP under different aging times, salinity, and temperature conditions. The results demonstrated that the presence of the SiO2-NP significantly improved the viscosity and viscoelastic properties of the HPAM under high temperature and high salinity (HTHS) conditions [80]. Haruna et al. grafted HPAM molecules with graphene oxide (GO) nanosheets and evaluated the rheological and stability properties of the formulated polymeric nanofluid. They reported enhancement of the suspension viscosity behavior, as well as high-temperature stability and

As for polymer-coated nanoparticles, depending on the grafting method, the polymeric chains protrude from the nanoparticle surface. Hence, hydrodynamic interactions occur between the grafted nanoparticle when subjected to shear. Besides, polymeric chains grafted on the surface of the nanoparticle overlap with another polymer chain adsorbed on another nanoparticle. The overlapping of

agglomeration problems of nanoparticles at reservoir conditions. It involves grafting polymers onto the surface of nanoparticles to improve dispersibility. In addition, their properties can be customized for particular applications [34]. Meanwhile, polymer nanoparticles are prepared by the hybrid dispersion of nanoparticles in polymer solutions. These polymer nanoparticles emerged as a means of inhibiting polymer degradation in typical reservoir conditions [4]. The mechanisms of polymeric nanofluids performance during EOR applications include improved rheology

and stability, wettability alteration, and lower polymer adsorption [6].

3.2.1 Improved rheology and stability for mobility control

Enhanced Oil Recovery Processes - New Technologies

of the polymer and the stability of the nanoparticle [4].

improved elastic properties of the dispersion [85].

of the polymer molecules [81].

38

Polymeric nanofluids also show reduced adsorption onto porous media due to the synergic interaction between the polymer and nanoparticles. Foster et al. used the grafting through approach to tether tuneable quantities of poly(2-acrylamido-2 methylpropanesulfonic acid) (PAMPS) and poly([3-(methacryloxylamino)propyl] dimethyl(3-sulfopropyl)ammoniumhydroxide)(PMPDSA) homopolymer (PMPDSA) onto iron oxide nanoparticle surfaces. Steric stabilization of the synthesized polymer-coated nanoparticle was observed which remained stable at HTHS conditions. Moreover, adsorption experiments on crushed Berea sandstone cores showed that the adsorption of polymer-coated iron oxide nanoparticles was


Table 3. Laboratory results of oil recovery applications by polymeric nanofluid [6]. infinitesimal and almost negligible [96]. Cheraghian et al. performed static adsorption experiments to investigate the impact of nano-SiO2 and nanoclay on the adsorption inhibition of polyacrylamide onto sandstone rocks. Polymer nanoparticles containing SiO2 nanoparticle showed lower adsorption onto sandstone rock surface compared to the polymer containing nanoclay [97].

### 3.2.3 Wettability alteration

Wettability alteration plays a vital role in enhancing the microscopic displacement efficiency. In the case of polymeric nanofluids, an interplay of electrostatic repulsive forces occur at the interface of the nanoparticles., Two-dimension layered structure of nanoparticles occur due to Brownian motion when brought into contact with an oil-wet solid surface, creating a wedge film because of the ordering of nanoparticles at the three-phase (solid-oil–water) contact region. This results in an increase of the disjoining pressure,which causes the spreading of the nanofluid phase at the wedge of the vertex, altering the wettability of the surface [6]. Maurya et al. grafted polyacrylamide on the surface of SiO2 using the free radical polymerization approach and investigated its wettability potential on an oil-wet sandstone rock surface. They indicated that the polymer grafted nanoparticle altered the wettability of the sandstone surface to a more water-wet condition [86]. Maghzi et al. performed wettability alteration studies employing polymer nanoparticles consisting of SiO2 nanoparticle and polyacrylamide polymer solution in a five-spot glass micromodel. The polymer nanoparticle altered the surface of the micromodel from an average contact angle of 112° (oil-wet) to 20° (water-wet). More details of wettability alteration by polymeric nanofluids can be found in the literature [6, 34].

### 4. Conclusions

This chapter summarizes some of the recent advances in the application of nanotechnology in chemical EOR processes to boost oil production. The mechanisms of oil recovery through nanotechnology were reviewed. Several experimental studies were summarized and discussed. Results of various experiments shows that the incorporation of nanotechnology with chemical EOR shows good potential to improve pore scale mechanisms in the case of surfactant. Adsorption of surfactant on rock pores is inhibited while greater IFT reduction and better wettability alteration were achieved. Furthermore, nanotechnology improved the rheological properties of polymer and stability of emulsions and foams indicating the good potentials of improving sweep efficiency of injected chemicals especially in the presence of harsh reservoir conditions. Finally, future research should focus on modeling the flow behavior of nanomaterials through porous media, which is required for the designing and field implementation of nano-chemicals EOR.

### Nomenclature


Nanotechnology Application in Chemical Enhanced Oil Recovery: Current Opinion and Recent… DOI: http://dx.doi.org/10.5772/intechopen.88140

