Hydrophobically Modified Polyacrylamide Research Articles

The effect of amphiphilic monomer on the interaction between amphiphilic polyacrylamide and crude oil on the solid surface

Hydrophobically modified polyacrylamide (HMPAM) is one of most used amphiphilic polymers for polymer flooding in oilfield. The interaction between HMPAM and crude oil is key to the oil displacement efficiency of HMPAM. However, due to the lack of experimental research method, there is little research on this aspect. In this work, HMPAMs containing different types of amphiphilic monomers were prepared, their interactions with crude oil were studied by dual polarization interferometry (DPI) for the first time, and their adsorption conformations on the surface of crude oil were discussed. The DPI results directly shown that the influence of amphiphilic monomer type on the interaction strength was as follows: nonionic type > cationic type ≈ anionic type. This order was consistent with the adsorption capacity of amphiphilic monomer on the surface of crude oil, indicating that the interaction strength between HMPAM and crude oil mainly depended on the type of amphiphilic monomers. In addition, the DPI results indirectly shown that the effect of amphiphilic monomer type on the HMPAM molecular coiled conformation on the surface of crude oil was also determined by the adsorption capacity of amphiphilic monomer. The research results of this paper can provide useful information for the amphiphilic monomer selection from the perspective of improving oil displacement efficiency of HMPAM.

Demulsification law of polyether demulsifier for W/O crude oil emulsion containing hydrophobically modified polyacrylamide in water

Hydrophobically modified polyacrylamide (HMPAM) is one of the commonly used polymers for polymer flooding. Because it is water soluble, there are many reports on the impact of HMPAM on the stability and treatment of produced water (it is O/W emulsion), but few reports on its influence on the demulsification of W/O crude oil emulsion. In this paper, firstly, three types of HMPAM containing cationic, anionic, and nonionic hydrophobic monomers (abbreviated as P(AM-AANa-N)Cn, P(AM-AANA-S)Cn, and P(AM-AANA-O)Cn, respectively) were synthesized; Then, demulsification experiments and interface behavior experiments (including dynamic interfacial tension, dilatational rheology and dynamic coalescence time measurement) were conducted to investigate the influence of HMPAM on the demulsification performance of a W/O heavy oil emulsion demulsifier D1. The demulsification results showed that HMPAM reduced the dehydration speed of D1, the type of hydrophobic monomer and the length of hydrophobic chain in HMPAM can affect the final water separated of D1. P(AM-AANa-S)Cn, P(AM-AANa-N)Cn with long hydrophobic chain, and P(AM-AANa-O)Cn with short hydrophobic chains had the negative effect on performance of D1. The results of dynamic interfacial tension experiments indirectly showed that HMPAM had the influence on the D1′s conformation and speed of rearrangement at the W/O interface during the water droplet coalescence process, thereby affecting the reduction of elastic modulus (G′) of W/O interface and the coalescence rate of water droplets. When there was HMPAM in water, the coalescence time of water droplets increased, resulting in the decrease of dehydration rate. At the meantime, HMPAM had an impact on the lg(G1′/Gdemulsifier′)/lgG1′, thereby affecting the final water separated of D1.

The effect of polymer on the floatation-flocculation performance of flocculant for treating polymer flooding produced water

In this paper, a series of hydrophobically modified polyacrylamide (HMPAM) containing different types of hydrophobic monomer were synthesized. Their effects on the performance of a typical flocculant DA, which was used in air floatation cyclone and is a copolymer of tertiary amine monomer and polymerizable polyether, were investigated. The experimental results showed that low concentration (≤200 mg/L) of HMPAM improved the oil removal performance of DA, and high concentration of HMPAM greatly reduced the oil removal performance of DA. It was proposed that the electrostatic attraction between HMPAM and DA had both the positive and negative effects on performance of DA, and which one dominated was influenced by HMPAM concentration. This propose was confirmed by the results of dynamic light scattering and zeta potential. In addition, we found that the negative effect decreased with the increasing hydrophobic monomer chain. The results of this study can provide a guidance for the synthesis and selection of HMPAM from the perspective of produced water treatment.

The effect of HMPAM on performance of nonionic polyether water clarifier from the perspective of HLD theory

Nonionic polyether water clarifier is commonly used in the treatment of produced water from offshore oilfield. At the meantime, hydrophobically modified polyacrylamide (HMPAM) is one of the commonly used polymer oil displacement agents. Predicting the influence of HMPAM on the performance of nonionic polyether water clarifier is of great significance for the treatment of produced water. This work explored the influence of different HMPAMs on the hydrophilic-lipophilic deviation (HLD) equation of a typical nonionic polyether water clarifier AE411 based on the HLD theory, and predicted their influences on the performance of AE411. The results showed that HMPAM had no effect on the parameter K (reflecting the interaction between AE411 hydrophilic groups and oil phase) and ct (reflecting the temperature sensitivity of AE411) in HLD equation of AE411, but reduced the parameter Ccn (reflecting the micelle structure of AE411 in water) and led to an increase in temperature corresponding to AE411′s HLD = 0. It was predicted that higher temperature was needed to ensure the performance of AE411. The experimental results of produced water treatment confirmed this prediction. The results of the paper validated the reliability of HLD application in the field of produced water treatment and provided some guidance for the development of nonionic polyether water clarifier.

The Interfacial Dilational Rheology Properties of Betaine Solutions: Effect of Anionic Surfactant and Polymer.

Interfacial dilational rheology is one of the important means to explore the interfacial properties of adsorption films. In this paper, the interfacial rheological properties of the mixed system of sulfobetaine ASB with a linear alkyl group and two anionic surfactants, petroleum sulfonate (PS) and alkyl polyoxyethylene carboxylate (AEC), were investigated by interfacial dilational rheology. The effect of the introduction of polymer hydrophobically modified polyacrylamide (HMPAM) on the interfacial properties of the mixed system was analyzed. In this experiment, the surfactant solution was used as the external phase and n-decane was used as the internal phase. A periodic sinusoidal disturbance of 0.1 Hz was applied to the n-decane droplets, and the changes of parameters such as droplet interfacial tension and interfacial area were monitored in real time with the help of a computer. The results show that the betaine ASB molecule responds to the dilation and compression of the interface through the change of ion head orientation, while the feedback behavior of petroleum sulfonate PS and AEC molecules embedded with oxygen vinyl groups in the molecule is diffusion and exchange between the interface and the bulk phase. Therefore, the interface film formed by ASB alone is higher, and the film formed by PS and AEC molecules alone is relatively lower. After adding two kinds of anionic surfactants to the betaine system, the ionic head of PS or AEC molecules will be attached to the positive center of the hydrophilic group of ASB molecules by electrostatic attraction and no longer adsorb and desorb with the interface deformation. The interfacial rheological properties of the compound system are still dominated by betaine, with higher dilational modulus and lower phase angle. When a small amount of HMPAM is added, or the content of hydrophobic monomer AMPS in the bulk phase is low, the intermolecular interaction at the interface is enhanced, the slow relaxation process is intensified, and the interfacial film strength is increased. As the content of AMPS further increases, hydrophobic blocks and surfactant molecules will form interfacial aggregates similar to mixed micelles at the oil-water interface, which will regulate the properties of the film by affecting the adsorption of surfactants at the interface. As long as the interfacial tension is the same, the properties of the interfacial film are the same. Based on the colloid interface science and the background of enhanced oil recovery, this study provides a reference for the field application of chemical flooding formulations.

Tough, self‐healing double network hydrogels crosslinked via multiple dynamic non‐covalent bonds for strain sensor

AbstractDouble‐network hydrogels have outstanding mechanical characteristics but mostly suffer from poor self‐healing performance since most hydrogels are chemically crosslinked via covalent links for each network. In this work, a tough and self‐healing double network hydrogel with multiple dynamic non‐covalent bonds is developed by combining the hydrophobically modified polyacrylamide (HPAM) with a thermally reversible potassium ion crosslinked κ‐carrageenan (K+C) network through a dual physical crosslinked network strategy. Being the multiple dynamic non‐covalent bond interactions and dual physical crosslink networks, the K+C/HPAM DN hydrogel exhibits excellent mechanical characteristics (tensile strength: 1.86 MPa, tensile strain: 1637%) and good self‐healing ability (maximum stress self‐healing efficiency: 87%, maximum tensile strength after self‐healing: 0.95 MPa). Due to the three‐dimensional pore structure and the conductive ions in the system, the K+C/HPAM DN hydrogel also achieves good strain sensing capabilities with a strain sensitivity of 2.98 (gauge factor, GF) in the 100% strain range. Even after being cut and self‐healed, the gel still exhibits good strain sensing capabilities (GF = 2.79), which is still better than the most similar DN hydrogel strain sensors in sensitivity. We believe this work offers a new material for self‐healing flexible strain sensors.

The Synergistic Effects between Sulfobetaine and Hydrophobically Modified Polyacrylamide on Properties Related to Enhanced Oil Recovery

In order to explore the mechanism responsible for the interactions in the surfactant-polymer composite flooding and broaden the application range of the binary system in heterogeneous oil reservoirs, in this paper, the influences of different surfactants on the viscosity of two polymers with similar molecular weights, partially hydrolyzed polyacrylamide (HPAM) and hydrophobically modified polyacrylamide (HMPAM), were studied at different reservoir environments. In addition, the relationship between the surfactant-polymer synergistic effects and oil displacement efficiency was also investigated. The experimental results show that for HPAM, surfactants mainly act as an electrolyte to reduce its viscosity. For HMPAM, SDBS and TX-100 will form aggregates with the hydrophobic blocks of polymer molecules, reducing the bulk viscosity. However, zwitterionic surfactant aralkyl substituted alkyl sulfobetaine BSB molecules can build "bridges" between different polymer molecules through hydrogen bonding and electrostatic interaction. After forming aggregates with HMPAM molecules, the viscosity will increase. The presence of two polymers all weakened the surfactant oil-water interfacial membrane strength to a certain extent, but had little effect on the interfacial tension. The synergistic effect of the "bridge" between HMPAM and BSB under macroscopic conditions also occurs in the microscopic pores of the core, which has a beneficial effect on improving oil recovery.

Dynamic interfacial tensions of sulfobetaine and polymers solutions: Effect of structures

To facilitate the understanding of the intrinsic mechanism responsible for the IFTs of betaine solutions, partly hydrolyzed polyacrylamide (HPAM) and hydrophobically modified polyacrylamide (HMPAM) were employed to investigate their effect on IFTs of different betaine solutions against decane using a spinning drop interfacial tensiometer. Moreover, the effects of oleic acid on the IFTs of betaine-polymer systems were also studied. The results show that the water-soluble polymers (HPAM) form the mixed adsorption film with alkyl sulfobetaine (ASB) molecules and prevent the hydrophilic groups of ASB from lying flat, which produces a minimum IFT with aging time. Besides, the hydrophobic HMPAM forms mixed micelle-like interfacial associations with ASB molecules, which results in a stronger disruption tendency for the interfacial film. The branched xylyl substituted alkyl sulfobetaine (BSB) molecules will form a tight interfacial film, therefore HPAM can’t insert into the interfacial film easily. Meanwhile, steric hindrance makes it difficult to form interfacial aggregates with HMPAM. Thus, the addition of HPAM and HMPAM polymers has little influence on the IFTs in the BSB system. The mixed adsorption of oleic acid and betaine molecules results in a significant decrease in IFTs, especially for BSB. However, in the ASB-polymer system, HPAM forms mixed adsorption film with ASB molecules and hinders the adsorption of oleic acid, accordingly IFTs change little. In contrast, the hydrophobic interaction of HMPAM promotes the adsorption of oleic acid, so the synergistic effect reduces IFTs to some extent. In the BSB-polymer system, the strong synergistic effect between oleic acid and BSB molecules is disrupted by polymers, which results in a significant increase in IFTs. The relevant results are helpful for the design of novel and efficient chemical flooding systems.

Enhanced hydrophobically modified polyacrylamide gel for lost circulation treatment in high temperature drilling

Cross-linked polymer gels have attracted a strong interest for lost circulation treatment in drilling operation. However, the application of gels in high temperature loss zone was still limited due to the problems of short gelation time, weak strength, poor thermal stability, etc. In this paper, a novel cross-linked modified polyacrylamide gel (HMP-Gel), which consisted of a hydrophobically modified polyacrylamide (HMP) and crosslinker polyethyleneimine (PEI), was designed and developed. The novel HMP was synthesized to form and strengthen the gel structure due to the crosslinkable amide groups and associable hydrophobic moieties, and PEI was used to extend gelation time at high temperature. In detail, the HMP of acrylamide (AM), octadecyl acrylate (OA), and 2-acrylamide-2-methylpropanesulfonic acid (AMPS) was prepared using micellar copolymerization under the best conditions. The molecular structure of HMP was characterized using FT-IR, gel permeation chromatography and environmental scanning electron microscope (ESEM). In gelation process, effects of PEI concentration, HMP concentration, temperature and salinity on gel performance (plugging efficiency and gelation time) were systematically investigated. Plugging performance of HMP-Gel was studied using both the HTHP carbonate bed filtration loss test and HTHP crack plugging test. Rheological property of HMP-Gel was studied to access the elastic properties and gel strength. Results of various factors on gel performance indicated that HMP-Gel showed the good plugging efficiency for carbonate bed and controllable gelation time in the temperature range of 100–150 °C. Results from plugging tests indicated that the HMP-Gel had better sealing ability than HPAM-gel for both the high permeable carbonate bed and 1-3 mm cracks loss zone. And the breaking pressure of HMP-Gel could reach 1000 psi and 600 psi for carbonate bed and 3 mm slot, respectively. Additionally, HMP-Gel also showed high elasticity, gel strength, and excellent thermal stability at 140 °C. Finally, the micro-morphology of gel was further analyzed through ESEM. A new strategy of using hydrophobically modified polyacrylamide to strengthen the gel structure was proposed, and extensive laboratory tests suggested that HMP-Gel could be considered as an efficient plugging material and showed great potential in applications for lost circulation in high-temperature well.

Self-assembly in amphiphilic spherical brushes.

The structure of amphiphilic spherical brushes, consisting of the nano-SiO2 core, the hyperbranched polyamidoamine subshell, and a grafted layer of long hydrophobically modified polyacrylamide (HMPAM) chains, in aqueous solution was analyzed and described in the framework of the original mean-field approach. The scaling estimations of the hydrodynamic radius of such polymer brushes as a function of the number of grafted macromolecules allow concluding that the HMPAM shells are in a globular state and that the region of the stretched chains adjacent to the grafting surface is a minor part of the grafted macromolecules and does not have a significant impact on the self-assembly of the HMPAM shell caused by the complex hydrophobic-hydrophilic composition of their monomer units. In mean-field theory, the amphiphilic nature of HMPAM was taken into account by attaching the hydrophobic side group H to some fraction of monomer units of the hydrophilic P backbone. The strong attraction of H groups causes the aggregation of macromolecules, whereas the affinity of hydrophilic P groups to solvent forces the aggregates to increase their surface. Due to such effective surface activity, in poor solvent, the grafted amphiphilic macromolecules could form a spherical compacted structure around the nanoparticle or self-assemble into a "hedgehog" structure with several "spines" having hydrophobic core and hydrophilic shell. State diagrams, obtained theoretically, reveal that the "hedgehog" structure is preferable for a wide range of energetic parameters.

Effect of salinity on adsorption and interaction forces of hydrophobically modified polyacrylamide on silica and alumina surfaces

In this work, the adsorption behaviors and interaction forces of different polymers on silica and alumina surfaces have been investigated under the effect of KCl concentration using quartz crystal micro-balance with dissipation (QCM-D) monitoring technique, viscosity measurement and atomic force microscopy (AFM) colloidal probe technique. Polyacrylamide (PAM) and hydrophobically modified polyacrylamide (HMPAM) with hydrophobic monomer (i.e., hexadecyl dimethyl allyl ammonium chloride (C16DMAAC)) have been investigated as model polymers. It is found that the adsorption amounts of HMPAM and PAM polymers on negatively charged silica and positively charged alumina surfaces increase with increasing solution salinity (1–100 mM KCl). HMPAM displays higher adsorption capacity than PAM on both silica and alumina surfaces, which is attributed to the hydrophobic interaction originated from the long hydrocarbon chains of HMPAM. Furthermore, the measured adhesion between the polymers and the substrate surfaces is found to decrease for the alumina cases and increase for the silica cases with increasing the salinity, which is due to the weakened electrostatic interactions between the polymers and substrate surfaces under high salinity (i.e., 100 mM KCl). The viscosities of PAM and HMPAM solutions are found to decrease with increasing solution salinity, which could be caused by the much more coiled conformation of PAM and HMPAM chains at higher salinity. Both the interactions between the polymer and substrate surface and the polymer conformational changes play important roles in the polymer adsorption behaviors on silica and alumina surfaces.

Interaction and Adsorption of Hydrophobically Modified Polyacrylamide on Silica and Asphaltene Surfaces

The adsorption of polymers affects the cost and oil recovery in oil reservoir exploitation and the flocculation effect in the treatment of oil sand tailings. The adhesion and adsorption of a hydrophobically modified polyacrylamide (HMPAM), i.e., P(AM-NaAA-C16DMAAC), on silica and asphaltene were investigated using surface force measurements, thermodynamic analysis and quartz crystal microbalance with dissipation (QCM-D) measurement. Our study indicates that HMPAM polymer has strong interaction with both silica and asphaltene. The adhesion force of HMPAM on silica was stronger than that on asphaltene surface. Consistently, the adsorption of HMPAM was also greater on silica surface, with a more rigid layer formed on the surface. For HMPAM/silica system, the attractive interaction and the strong adhesion are mainly driven by the hydrogen bonding and electrostatic interaction. For HMPAM/asphaltene system, it is mainly due to hydrophobic interaction between the long hydrocarbon chains of HMPAM and asphaltene. Furthermore, continuous adsorption of HMPAM was detected and multiple layers formed on both silica and asphaltene surfaces, which can be attributed to the hydrophobic chains of HMPAM polymers. This work has illustrated the interaction mechanism of HMPAM polymer on hydrophilic silica and hydrophobic asphaltene surfaces, which provide insight into the industrial applications of hydrophobically modified polymer.

Characterization of Hydrophobically Modified Polyacrylamide in Mixed Polymer-Gemini Surfactant Systems for Enhanced Oil Recovery Application.

The study deals with the synthesis and characterization of the hydrophobically modified polyacrylamide (HMPA) copolymer and its functional property evaluation in mixed polymer-gemini surfactant systems for application in enhanced oil recovery (EOR). The copolymer was initially prepared in the laboratory using acrylamide and N-phenylacrylamide monomer units via an addition polymerization route. The synthesized copolymer was characterized by Fourier transform infrared and proton nuclear magnetic resonance to identify suitable functional groups in the compound. Gel permeation chromatography tests showed that the polymer has a molecular weight of 2.098 × 105 Da. Copolymer solution showed favorable tolerance to variations in temperature and salinity. Salt precipitation studies identified tolerance limit up to 25% NaCl at a temperature of 343 K. Viscosity of HMPA fluids showed an increase with increasing concentration. Interestingly, salt addition until 1.0% NaCl showed an increase in solution viscosity owing to the electrostatic shielding of the HMPA polymer and strengthened intermolecular association of the hydrophobic groups. This behavior is against physicochemical properties observed in the case of conventional polymers but exhibits promising functionality in EOR processes wherein better oil mobility control is desired under subsurface conditions. Gemini surfactants accommodate onto “vacant adsorption” sites onto the liquid surface, improving the interfacial adsorption property and reducing surface tension. In the presence of gemini surfactant polymers forming mixed nanoemulsion fluid systems with favorable pseudoplastic character, their viscosities initially increase with surfactant concentration due to binding of surfactant molecules to hydrophobic junctions of polymer chains to form mixed micelles. Eventually, polymer hydrophobes get saturated with surfactant micelles, and viscosity decreases due to electrostatic repulsion among surfactant micelles. Dynamic light scattering analyses confirmed the formation of nanoemulsion droplets with sizes of <310 nm in the case of {surfactant + copolymer} encapsulation. Zeta potential measurements showed that an increase in 14-6-14 gemini surfactant concentration enhanced the stability of nanoemulsion fluid due to increasing zeta potential values. However, the nonionic SF-6-SF surfactant does not affect the zeta potential of nanoemulsions. Surfactant addition reduced the oil-aqueous interfacial tension of polymer solutions to several magnitudes of an order of 10–1 to 10–2 mN/m. Contact angle studies identified the ability of the polymer as well as polymer-surfactant nanoemulsions to alter the wettability of the reservoir rock from the intermediate-wet (90°–120°) to strongly water-wet state (<20°) at different temperatures. Analyzed formulations showed favorable miscibility with crude oil at 343 K. In summary, HMPA/gemini surfactant-based emulsions possess promising physicochemical and stabilization attributes for application in EOR.

Effect of salinity on adsorption of sodium hexametaphosphate and hydrophobically-modified polyacrylamide flocculant on kaolinite Al-OH surface

Solution salinity is critical for the inhibition effect of sodium hexametaphosphate on different mineral surfaces, further affecting the separation of minerals in aqueous solution. In this work, the effect of K+ and Ca2+ on adsorption of sodium hexametaphosphate (SHMP) and hydrophobically modified polyacrylamide, poly(AM-NaAA-C16DMAAC) (HMPAM), on alumina surface (i.e., kaolinite Al-OH surface) were investigated using quartz crystal microbalance with dissipation (QCM-D). The deposition layer on alumina surface with the effect of adding 1 mM SHMP in 10 mM of CaCl2 solution were examined by glancing angle X-ray diffraction (GAXRD), scanning electron microscope (SEM) and X-ray photoelectron spectroscopy (XPS). The 100 mM KCl solution promoted the adsorption of both HMPAM and SHMP on alumina surface, which would be mainly caused by the molecular configuration change. The more flexible and coiled configuration of HMPAM and SHMP in 100 mM KCl solution could be helpful for increasing the adsorption sites on alumina surface. Moreover, the intermolecular hydrophobic interaction between the alkane chains of HMPAM would lead to the multilayer adsorption of HMPAM instead of adsorbing directly onto alumina surface. Alternatively, 1 mM and 10 mM CaCl2 solutions lead to a lower adsorption amount of HMPAM on alumina surface, which is most likely caused by the suppressed electrostatic attraction and condensed conformation of HMPAM. The adsorption layer of SHMP formed on alumina surface could prevent the adsorption of HMPAM through different mechanisms in KCl and CaCl2 solutions at different concentrations. Interestingly, scattered micro-spheres were found to adsorb on alumina surface with 1 mM SHMP in 10 mM CaCl2 solution, mainly in forms of calcium hydrogen phosphate hydrate. Our work provides fundamental insights into the effect of adding dispersant (e.g., SHMP) and polymer flocculant (e.g., HMPAM) during selective flocculation of kaolinite, with helpful guidance for clay-involved mineral processing.

Study on rheological behavior and salt-thickening mechanism of a synthesized twin-tailed hydrophobically modified polyacrylamide

Hydrophobically modified polyacrylamide (HMPAM) is widely used in petroleum development, whereas it still confronts challenges in high salinity reservoirs. In this work, a twin-tailed modified polyacrylamide was introduced and characterized by FT-IR, 1H NMR and TGA. The rheological properties and thickening mechanism were investigated by viscosimetry, rheology, macroscopic appearance, dynamic light scattering, fluorescence spectroscopy and β-cyclodextrin inclusion. The results revealed that by increasing NaCl from 0 to 50 g/L, the critical association concentration declined and solutions transformed from a transparent fluid of 115 mPa·s to viscoelastic fluid of 2040 mPa·s. Eventually, the viscosity decreased with white precipitation at 200 g/L NaCl. The salinity conduced to the aggregate of hydrophobic groups, while excessive aggregate decreased the hydrodynamic volume, which in turn caused a reduction of macroscopic viscosity. Higher polymer concentrations were conducive to better salt-thickening property. This copolymer showed great salt resistance and prospects for application in high salinity reservoirs.

Effect of 1-octanol on the stabilization of crude oil emulsions with hydrophobically modified polyacrylamide

The formation of a stable crude oil emulsion is of great significance for enhancing oil recovery in oilfield development. The effect of 1-octanol (C8OH) on the emulsifying properties of hydrophobically modified polyacrylamide (HMP) was studied based on a novel multiple light scattering method. The emulsions stabilized by different polymer systems were evaluated in terms of stability and rheological properties. The obtained results show that the combined system of HMP + C8OH gives more stable emulsion with smaller droplet size compared to individual HMP. There is a strong bulk and interface interaction between HMP and C8OH for stabilizing emulsions, while such effect was observed neither between partially hydrolyzed polyacrylamide and 1-octanol nor between HMP and 1-octane. In the bulk phase of aqueous solution, the C8OH can be solubilized in the micro-domains of HMP, enhancing the intermolecular association structure and slowing down the creaming rate of the corresponding emulsions. The adsorption at the oil-water interface of HMP can be enhanced and tighter interfacial film can be formed due to the formation of the hydrogen bond between HMP and C8OH. The obtained results are of obvious importance for designing the amphiphilic polymer-containing emulsion more suitable to improve oil recovery as well as for better understanding the self-assembling mechanism of amphiphilic polymers and fatty alcohols.

A multi-scale experimental study of hydrophobically-modified polyacrylamide flood and surfactant-polymer flood on enhanced heavy oil recovery

A large amount of residual oil remained in heavy oil reservoirs after water flood due to its viscosity nature. And it has been validated that chemical flood, if applied appropriately, is an efficient and economical EOR method for deeply buried or thin heavy oil reservoirs. A multi-scale experimental evaluation workflow was designed to explore the mechanisms behind the production of residual oil in heavy oil reservoirs by chemical flood. And we conducted three multi-scale experiments to evaluate the performance of hydrophobically-modified polyacrylamide (HMHPAM) flood, surfactant-polymer (SP) flood and their combination. Based on the results of corefloods and medical CT scans, we demonstrated the EOR potential of HMHPAM flood (HPF) synergy with SP flood (SPF). After each coreflood, two samples were drilled from the heterogenous core used in the macro-scale experiment. And the micro-CT scan results of these samples visualized the distribution of oil phase and aqueous phase in each coreflood at the pore scale, and further quantified the decrease of continuous oil clusters caused by the HMHPAM solution and following injected fluids. Besides, we also observed the linear relationship between the volume of each oil cluster against its surface area and the logarithmic relationship between the volume of discontinuous oil cluster and its cumulative contribution to total oil volume. Moreover, a simple method to calculate the oil-water proportion in pores was developed to correlate the relationship between the displacement efficiency of each pore and its pore size. Results showed that the relationship between oil saturation in each pore and its pore size followed the power law correlation. Moreover, the pore-scale analysis also validated that the residual oil in most pores after water flood was effectively mobilized by the synergy of HPF and SPF.

Interaction of Amphiphilic Polymers with Medium-Chain Fatty Alcohols to Enhance Rheological Performance and Mobility Control Ability

To improve the efficiency of mobility control for polymer flooding, a novel thickening system was formed by adding medium-chain fatty alcohols to hydrophobically modified polyacrylamide (HMPAM) bri...

Studies of interfacial interactions between petroleum acids and associating polyacrylamide by dilational rheological measurements

In the present work, the interfacial dilational properties of hydrophobically modified polyacrylamide (HMPAM) at the kerosene/water interface were investigated by means of drop shape analysis method. The influence of petroleum acids on the dilational rheological behavior of HMPAM was expounded. The experimental results show that the dilational modulus of HMPAM layer can arrive at a high value of 80 mN/m for 2000 ppm polymer solution due to the formation of interfacial net structure by interactions among hydrophobic blocks of different HMPAM molecules. The petroleum acids molecules can interact with the hydrophobic blocks of HMPAM and form mixed micelle-like associations at interface, which will produce new fast relaxation process involving exchange of acid molecules between interfacial aggregates and free monomer at low HMPAM concentration, and destroy the interfacial net structure at high HMPAM concentration, respectively. Therefore, the moduli of HMPAM decrease obviously after adding petroleum acids, especially at higher HMPAM concentration.

Preparation and solution properties of a novel cationic hydrophobically modified polyacrylamide for enhanced oil recovery

A novel cationic water-soluble monomer allyldimethylisooctylammonium bromide (ADIAB) containing a short-chain alkane was synthesized successfully. This monomer was copolymerized with acrylamide and sodium acrylate to produce hydrophobically modified polyacrylamide (HMPAM) using solution polymerization without surfactants. The structures of monomer ADIAB and HMPAM were characterized with infrared spectroscopy and nuclear magnetic resonance spectroscopy. Influence of preparation condition on viscosities of products was studied. The aqueous solution viscosity of the terpolymer was also investigated as functions of concentration, temperature and salinity. The results showed that when the temperature exceeds the 60 °C and NaCl concentration exceeds about 2000 mg/L, the temperature and salt tolerance characters of terpolymer were demonstrated. The enhanced oil recovery tests were initially carried out using homogeneous sandpack models.