Surface Modified Polymers and Nanoparticles for Enhanced Oil Recovery (EOR) Application
Authors:   , Al-Shatty Wafaa 
Published: July 2022

The study to improve hydrocarbon recovery has attracted a great deal of research at-tention in many directions such as using chemical treatment or CO2 injection, and hydrocarbon fracking. The research trials are based on either studying a new approach to recovery or investigating the effect of injection agent treatments. Nanoparticles are a chemical addition that has promise in changing the reservoir properties through dif-ferent mechanisms such as: wettability alteration, reduce oil/water mobility, increase viscosity, disjoining pressure and interfacial tension reduction. In this thesis, alumina nanoparticles were modiﬁed with carboxylic acids to form different degrees of the hy-drophobicity. They were investigated as potential candidates for enhanced oil recov-ery applications. Surface modiﬁcation of alumina nanoparticles occurs at a molecular level. Consequently, applying these modiﬁcations for use as in the chemical treatment of Enhanced oil recovery (EOR) processes could change surface properties of oil, wa-ter, and rock. Thus, these modiﬁed alumina particles can act as a surface-active agent. Their increasing level of the hydrophobicity (depending on the type of carboxylic acid attached) and concentration shows a reduction in the interfacial tension (IFT) of hex-adecane oil. As a result, the ability to modify the degree of hydrophobicity makes them good candidates for EOR.Carboxylic acid-functionalized alumina nanoparticles (NPs) were tested as a poten-tial candidate for enhanced oil recovery. The NP’s size and shape in aqueous solution were investigated by dynamic light scattering (DLS) and small-angle neutron scatter-ing (SANS) as a function of the substituents: 2-[2-(2-methoxyethoxy)ethoxy]acetic acid (MEEA), and Octanoic acid (OCT). The viscosity and density of injected ﬂuids have been interpreted in terms of the NP’s chemical functionality. The inﬂuence of NPs hydrophobicity was observed in the size and oil removed from reservoir rock. The octanoic acid-functionalized alumina NPs is considered herein a good candidate for applications in oil recovery.The evaluation of the mechanism of nanoparticles/surfactant complex adsorption at the critical oil/water interface was studied with a sophisticated technique (Neutron Reﬂectometry) to give insight on nanoparticles/oil interactions in oil recovery systems. Here, the adsorption of two modiﬁed alumina nanoparticles with different degrees of hydrophobicity (hydrophilic 2-[2-(2-methoxyethoxy) ethoxy] acetic acid (MEEA), and hydrophobic octanoic acid (OCT)) stabilized with 2 different surfactants, were studied at oil/water interface. A thin layer of deuterated (D) and hydrogenated (H) hexade-cane (contrast matching Silicon substrate) oil was formed on a silicon block by a spin coating freeze process. The distribution of the NPs across the oil/water interface with CTAB surfactant is similar between the two systems. NPs coated with CTAB have more afﬁnity towards the oil/water interface, which explains the oil recovery increase by around 5% when ﬂooding the core with OCT-NP/CTAB system compared to the surfactant ﬂooding alone. These results suggest that NPs/surfactant complexes can have potential usage in EOR recovery applications.Chapter four addresses the challenge of the O/W Pickering emulsion formed with un/modiﬁed alumina nanoparticles adsorbed with surfactants showing longer stabil-ity. Alumina nanoparticles were modiﬁed by different carboxylic acids to acquire the different degrees of hydrophobicity. Dynamic light scattering and optical mi-croscopy measurements were then performed to characterize the aggregation behaviour of alumina-NP/surfactant’s mixture in an aqueous solution. The long-term stability of pickering emulsion stabilized by alumina modiﬁed nanoparticles was investigated di-rectly after each time interval: 5 min, 1 hour, 1 week, and 1 month. The result indicated that adjusting the amount of modiﬁed alumina nanoparticles and surfactants could be a suitable means for manipulating the stability of nanoparticles-surfactant based pick-ering emulsions. This would serve as a great application prospect for the preparation of pickering emulsion stabilized by eco-friendly nanoparticles (both MEEA and OCT) and surfactants.The synthesis and characterization of two new families of amphiphilic graft copoly-mers (AGCs) are reported. The graft polymers were synthesized using the various molecular weight of polyethylene glycol (PEG) (as hydrophilic graft chains) and two different hydrophobic backbones (with a varied quantity of functional groups) using a “graft onto” technique. FTIR and 1H NMR characterizations were used to indicate and validate the synthesis of grafted copolymers. The length of the PEG was observed to correlate with the hydrophilic ratio. Increasing the chain length of PEG was ob-served to increase the hydrophilicity ratio (more grafted PEG more hydrophilic). Con-sequently, both hydrophobic backbones wettability (⇠ 90 - 110◦) altered upon grafting onto synthesis and the contact angle data showed that the higher molecular weightof grafted chains led to higher hydrophilicity of grafted polymers (∼ 11 - 65◦). The critical micelle concentrations (CMC) and surface activity (SFT) of AGCs in water were determined by the surface tension technique via the shape analyser (pendant drop method). It revealed that these polymers can act as polymeric surfactants with CMC of around 2-3 wt.%. Small-angle neutron (SANS) was used to examine the confor-mation of the AGCs in aqueous solutions which displayed the formation of ellipsoidal core-shell micelles. This research provides fundamental understandings of potentially important polymeric materials with a variety of applications from emulsiﬁers and drug carriers to enhance oil recovery additives.The synergetic effect of combing low salinity water with polymer injection meth-ods (polymer ﬂooding) is a promising technique for oil displacement (enhanced oil recovery) (EOR). The objective of this study was to investigate the effect of newly synthesized amphiphilic polymers on two potential applications: oil displacement and stabilized emulsion. To successfully displace the oil within the tested reservoir rock, the optimal concentration of NaCl ions was determined to be 1 wt.% in the low salinity polymer. To evaluate aggregation behaviour, the conformational change of the grafted polymers/amphiphilic polymers resulting from the effect of salt/NaCl addition was investigated by Small-angle X-ray scattering (SAXS). The polymers displayed an el-lipsoidal core-shell micelles conformation. The copolymers with higher hydrophilic grafts had lower emulsion stability due to the size of the aggregation particles being smaller, despite having higher oil recovery capability. These ﬁndings have a signiﬁcant potential impact on the oil industry which is to counteract current hazardous methods and overcome the high salinity environment of EOR.