Polyacrylamide Polymer Solutions Research Articles

Effect of silicon dioxide nanoparticles on the rheology properties of fresh and mechanically degraded hydrolyzed polyacrylamide polymer solutions

AbstractPartially hydrolyzed polyacrylamide is extensively utilized in enhanced oil recovery operations. However, its efficacy is compromised by mechanical degradation during transport through injection lines, valves, and reservoir, which leads to a reduction in the average molecular weight, diminishing the solution's viscosity and viscoelastic properties, critical for efficient oil displacement. In this investigation, we characterized the degree of mechanical degradation in HPAM solutions by evaluating shear and extensional rheological parameters preand post‐degradation. Mechanical degradation was induced by subjecting them to controlled flow through a valve featuring varying degrees of constriction and flow rates. Our results demonstrate a significant reduction in zero‐shear viscosity and high‐strain extensional viscosity of mechanically degraded solutions, with reductions of up to 64%. To mitigate this issue, we explored the incorporation of silica nanoparticles as a potential remedy for mechanical degradation. These nanoparticles strengthen the network structure of HPAM, thereby reducing its susceptibility to mechanical degradation. Our findings reveal that shear and extensional viscosities of mechanically degraded NPs‐HPAM solutions experienced only minimal reductions, dropping to 12% and 0%, respectively. This underscores the effectiveness of the nanoparticle‐enhanced HPAM solutions in preserving viscosity and viscoelasticity under mechanical stress, presenting a promising avenue for improving the robustness of EOR processes.

Microfluidic Study of Enhanced Oil Recovery during Flooding with Polyacrylamide Polymer Solutions.

A series of experiments have been carried out on the flooding of microfluidic chips simulating a homogeneous porous structure with various displacement fluids. Water and polyacrylamide polymer solutions were used as displacement fluids. Three different polyacrylamides with different properties are considered. The results of a microfluidic study of polymer flooding showed that the displacement efficiency increases significantly with increasing polymer concentration. Thus, when using a 0.1% polymer solution of polyacrylamide grade 2540, a 23% increase in the oil displacement efficiency was obtained compared to water. The study of the effect of various polymers on the efficiency of oil displacement showed that the maximum efficiency of oil displacement, other things being equal, can be achieved using polyacrylamide grade 2540, which has the highest charge density among those considered. Thus, when using polymer 2515 with a charge density of 10%, the oil displacement efficiency increased by 12.5% compared to water, while when using polymer 2540 with a charge density of 30%, the oil displacement efficiency increased by 23.6%.

Effect of Sand Grain on Adsorption of Xanthan Gum and Polyacrylamide

Polymer flooding is an Enhanced oil recovery (EOR) method using chemicals, such as xanthan gum and polyacrylamide which are widely used in the field. Polymer flooding can improve the mobility of the injection fluid, but in the reservoir the polymer has an interaction with sand known as adsorption which causes some of the polymer to be bound to the surface of the pore of sand, so that it has an impact on the ineffectiveness of the injection. The purpose of this study want to determine and compare the effect of sand grain on the adsorption of xanthan gum and polyacrylamide polymer solutions. Based on the experiment results, it was found that the increase in adsorption was proportional to the increase in polymer concentration. From two polymers used, xanthan gum showed lower adsorption than polyacrylamide. Based on the sand grain, the adsorption that occurs is greater in the grain size for large sand compare small.

Conformance Control in Oil Reservoirs by Citric Acid-Coated Magnetite Nanoparticles.

Reservoir conformance control methods may significantly improve enhanced oil recovery technologies through reduced water production and profile correction. Excessive water production in oil and gas reservoirs leads to severe problems. Water shutoff and conformance control are, therefore, financially and environmentally advantageous for the petroleum industry. In this paper, water shutoff performance of citric acid-coated magnetite (CACM) and hematite nanoparticles (NPs) as well as polyacrylamide polymer solution in a heterogeneous and homogeneous two-dimensional micromodel is compared. A facile one-step technique is used to synthesize the CACM NPs. The NPs, which are reusable, easily prepared, and environmentally friendly, are characterized using Fourier-transform infrared spectroscopy, field emission scanning electron microscopy, dynamic light scattering, and X-ray diffraction. The results confirm uniform spherical Fe3O4 NPs of an average diameter of 40 nm, well coated with citric acid. CACM NPs provide a high pressure drop coupled with an acceptable resistance factor and residual resistance factor owing to NP arrangement into a solid-/gel-like structure in the presence of a magnetic field. A resistance factor and a residual resistance factor of 3.5 and 2.14, respectively, were achieved for heavy oil and the heterogeneous micromodel. This structure contributed to an appreciable plugging efficiency. CACM NPs respond to ∼1000 G of magnetic field intensity and display a constant resistance factor at intensities between 4500 and 6000 G. CACM NPs act as a gel, forming a solid-/gel-like structure, which moves toward the magnetic field and thereby shuts off the produced water and increases the oil fraction. The findings of this study suggest the ability to shut off water production using specially designed magnetic field-responsive smart fluids. The application would require innovative design of field equipment.

Effect of water saturation on the role of polymer elasticity during heavy oil recovery

During enhanced oil recovery, polymers are used to improve the sweep efficiency during chemical injection process. Polymers are mainly characterized based on their viscoelasticity response; however, the role of polymer elasticity on heavy oil considering the effect of water saturation in porous media has not been well explored. In this work, four blends of polyacrylamide polymer solutions with similar molecular weight and shear viscosity but different bulk elasticity (due to different molecular weight distribution) were used. A series of flooding experiments were performed using a cylindrical core sand pack saturated with heavy oil designed to simulate linear flow. The flow rate was selected based on the shear rate range present in field applications. Effect of elasticity during the injection of these polymer solutions were compared during tertiary recovery experiments in terms of oil recovery and residual resistance factor at different initial water-flood volumes. The results indicate that the effect of polymer elasticity was more profound in tertiary mode with higher water saturation. An additional pressure drop was required to push a higher elastic solution. The required pressure drop to push the polymer solutions increased with water saturation.

Investigating fouling at the pore-scale using a microfluidic membrane mimic filtration system

The work investigates fouling in a microfluidic membrane mimic (MMM) filtration system for foulants such as polystyrene particles and large polymeric molecules. Our MMM device consists of a staggered arrangement of pillars which enables real-time visualization and analysis of pore-scale phenomena. Different fouling scenarios are investigated by conducting constant-pressure experiments. Fouling experiments are performed with three different types of foulants: polystyrene particle solution (colloidal fouling), polyacrylamide polymer solution (organic fouling) and a mixture of these two solutions (combined fouling). Four major categories of microscopic fouling are observed: cake filtration (upstream), pore blocking (inside the pores), colloidal aggregation (downstream) and colloidal streamer fouling (downstream). Our microfluidic experiments show that downstream colloidal aggregation and streamer fouling have a significant effect on overall membrane fouling which were not studied before.

Thermal Resistance and Application of Nanoclay on Polymer Flooding in Heavy Oil Recovery

High molecular weight and water-soluble synthetic organic polymers are currently being used in the field with the hope of enhancing the recovery of oil by water flooding. Nanotechnology has been used in many applications and new possibilities are discovered constantly. Recently, a renewed interest arises in the application of nanotechnology for the upstream petroleum industry. The author focuses on roles of clay nanoparticles on polymer viscosity. Polymer-flooding schemes for recovering residual oil have been in general less than satisfactory due to loss of chemical components by adsorption on reservoir rocks, precipitation, and resultant changes in rheological properties. Rheological properties changes are mainly determined by the chemical structure and mix of the polymers, surface properties of the rock, composition of the oil and reservoir fluids, nature of the added polymers, and solution conditions such as salinity and temperature. On the other hand, the author's focus is on viscosity, temperature, and salinity of solutions polyacrylamide polymer solutions with different nanoparticles. Results show that ultimate oil recovery by nanoclay polymer flooding enhances by a factor of 5.8% in comparison to polymer flooding high salinity and temperature.

Refractive Index Mismatch Can Misindicate Anomalous Diffusion in Single‐Focus Fluorescence Correlation Spectroscopy

Fluorescence correlation spectroscopy (FCS) is often used to study diffusion in complex media, wherein the refractive index usually differs from that of the immersion medium. This paper assesses the effect of this refractive index mismatch. Confocal single‐focus and two‐focus fluorescence correlation spectroscopy (2fFCS) is used to probe the diffusion of tagged dextran tracers in water, dilute dextran solutions, acrylamide monomer solutions, polyacrylamide polymer solutions, and a cross linked polyacrylamide hydrogel. In these experiments, both the refractive index and the potential topological constraint and thermodynamic interaction to the probe‐diffusion are varied, and pairs of samples with same refractive indexes but different compositions are compared. Whereas 2fFCS shows no anomalous diffusion in any of them, single‐focus FCS indicates anomalous diffusion. In particular, the values of the stretching exponent of the fluorescence autocorrelation function, which is often interpreted to reflect the extent of anomaly of diffusion, do not vary systematically with the extent of topological or thermodynamic complexity of the different matrixes, but with their refractive index. This shows that apparent anomalous diffusion in FCS is at risk to be the result of refractive index mismatch rather than reflecting truly complex diffusion. image

Effect of nanoclay on improved rheology properties of polyacrylamide solutions used in enhanced oil recovery

Recently, a renewed interest arises in the application of nanotechnology for the upstream petroleum industry. In particular, adding nanoparticles to fluids may drastically benefit enhanced oil recovery (EOR) and improve well drilling, by changing the properties of the fluid, rocks wettability alteration, advanced drag reduction, strengthening the sand consolidation, reducing the interfacial tension and increasing the mobility of the capillary trapped oil. In this study, we focus on roles of clay nanoparticles on polymer viscosity. Polymer-flooding schemes for recovering residual oil have been in general less than satisfactory due to loss of chemical components by adsorption on reservoir rocks, precipitation, and resultant changes in rheological properties. Rheological properties’ changes are mainly determined by the chemical structure and mix of the polymers, surface properties of the rock, composition of the oil and reservoir fluids, nature of the added polymers and solution conditions such as salinity, pH and temperature. On the other hand, in this study, the focus is on viscosity and salinity of solutions polyacrylamide polymer solutions with different nanoparticles degrees and molecular weight. Results in certain range of clay concentration used in this test, the way of clay adding, have positive effects on solution viscosity. The effect of the polymer content and salinity were also to be investigated.

Using MR techniques to probe permeability reduction in rock cores

AbstractPolymer solutions are used commonly in oil‐recovery applications to reduce water production. While the polymer treatment is known to modify the permeability of the rock, the mechanism by which this occurs is poorly understood, and, hence, the ability to optimize either the polymer solution or its application is restricted. In this work, the pulsed‐gradient spin‐echo nuclear magnetic resonance technique is used to determine displacement propagators (distributions) for brine solution flowing through a Bentheimer sandstone rock core, both before and after treatment of the rock core with a polyacrylamide polymer solution. A novel simulation strategy employing the lattice–Boltzmann method is then proposed to interpret the differences in these propagators in terms of the location of polymer retained within the pore structure of the rock following treatment. The results suggest that the polymer is preferentially trapped in comparatively low permeability pores.

The superposition of steady on oscillatory shear and its effect on the viscoelasticity of human blood and a blood-like model fluid

To understand the pulsatility of human blood flow in vivo, it is necessary to separately investigate (1) steady shear and oscillatory flow, and (2) the superposition of steady shear flow on oscillatory flow performed under in vitro conditions. In this study a variable steady shear rate was superimposed in parallel on oscillatory shear at a constant frequency (0.5 Hz) for human blood (45% hematocrit), and an aqueous polyacrylamide polymer solution (AP 30E, concentration 300 ppm). The effect of superposition of the above two shear flows on the viscoelasticity of blood was more pronounced for the elastic (η′') than for the viscous (η′) component of viscoelasticity. With increasing superimposed shear rate, both η′ and η′' decreased, especially at the low shear region. This behavior can be explained by the viscoelastic properties of blood and the phenomena of blood aggregation and disaggregation. Quantitatively, the dependence of the viscous component of complex viscosity on superimposed shear for both blood and polymer solution is described by a modified Carreau equation. The elastic component of complex viscosity decreased exponentially with increasing superimposed shear, and it is described by an exponential model. © 1997 Elsevier Science Ltd

Fluorescence-based polymerase chain reaction-single-strand conformation polymorphism analysis of p53 gene by capillary electrophoresis

Mutation of the p53 gene plays an important role in neoplastic progression in human tumorigenesis. Polymerase chain reaction-single-strand conformation polymorphism (PCR-SSCP) techniques are now available for the detection of point mutations. The original method using polyacrylamide gel electrophoresis is disadvattageous, particularly for clinical tests and for analysis of large numbers of samples. Therefore, using an automated capillary electrophoresis (CE) technique with a molecular-sieving polymer solution, we have devised a completely automatic fluorescence-based PCR-SSCP system (CE-FSSCP) for the differential detection of point mutations that dose not require SSCP with radioisotopes and polyacrylamide gels. This automatic CE-FSSCP system was developed for reproducible operations in the denaturation of double-stranded DNA and electrophoresis of single-stranded DNA. The detection system consists of a 100 W I 2 lamp and photomultiplier. We performed CE-FSSCP with a 2% linear polyacrylamide polymer solution containing 5% glycerol. Four tissue specimens of lung tumors with mutations in exon 7 of the p53 gene were found to have mutant alleles; a six-base-pair deletion at codons 247–248, a one-base-pair deletion at codon 260, a one-base-pair deletion at codon 244 and a GGC to CGC substitution at codon 244. We expect this technique to prove useful for the clinical DNA diagnosis of human cancers, determination of the therapeutic effect of anticancer agents and for the study of the molecular aspects of the mechanisms involved in the pathogenesis of human cancers.

EFFECT OF DEFORMATION SEQUENCE ON RHEOLOGICAL BEHAVIOUR AND MECHANICAL DEGRADATION OF POLYMER SOLUTIONS

The flow behaviour of polymer solutions of non-hydrolyzed polyacrylamide and Xanthan was investigated in two rectangular and similar plexiglas models containing 3 cylindrical enlargements of the same dimensions. These three enlargements were located successively at the mid point of the first model length, whereas they were equally spaced along the second one. Only non-hydrolyzed polyacrylamide polymer solutions have shown viscoelastic behaviour in these plexiglas models. However, the behaviour of these polymer solutions in the first model was different from that in the second one. The multipass mechanical degradation of the non-hydrolyzed polyacrylamide polymer solutions was studied extensively in the two plexiglas models. It was shown that, at high flow rates, the multipass mechanical degradation was stronger in the second model than in the first one. The mechanical degradation in model 1 converges with that in model 2 as the flow rate decreases. The difference in flow behaviour and mechanical degradatio...

The Effect of Temperature on Gelation Time for Polyacrylamide/Chromium (III) Systems

Abstract Gelled polymers are being applied to modify the movement of injected fluids in the vicinity of injection and production wells in secondary and enhanced oil-recovery projects. One approach to gelation is to form a bulk gel in situ by injecting a slug of a Polyacrylamide polymer solution containing chromium(VI) followed by a polymer slug containing a reducing agent such as sodium bisulfite. Upon mixing, CR(VI) is reduced to Cr(III), and in the subsequent reaction a gel is formed. The gelation time controls the volume of fluid that can be injected in the treatment and thus is an important variable in the process. Gelation time is known to be a function of the concentration of the reactants (chromium ion, reducing agent, and polymer) as well as the polymer type, and some data relating these variables to gelation time have been reported. Another variable affecting the reaction rate is temperature, but no data relating gelation time and temperature have been published. The purposes of the work described in this paper were to obtain experimental data on the effect of temperature on gelation time for typical polyacrylamide/Cr(III) gel systems over the range of temperatures commonly encountered in reservoirs and to develop a method of correlating the data. Gelation times were measured for five different polymers, including polymers with various degrees of hydrolysis and polymers with nonionic, anionic, and cationic character. The temperature range was 25 to 80°C. Polymer, metal ion, and redox system concentrations and salinity also were varied. It was determined that, for a given polymer-reducing agent system at a specified concentration, the gelation time decreases as temperature is increased. The data were correlated in a manner analogous to the Arrhenius method of correlating chemical reaction rate data. That is, plots of the logarithm of gelation time vs. the reciprocal of the absolute reaction temperature were linear over the temperature range studied. By use of a simple nth-order reaction rate model, the slope of the Arrhenius-type plot was related to activation energy. These activation energies were found to vary only slightly for the polymer systems and concentrations investigated. The results have direct application in the design of gel treatments for injection or production wells. The correlation method provides a way of predicting the effect of temperature on the time required for a given system to gel. It is recognized that in field applications factors beyond the scope of data taken in this paper may affect the gelation process.

Microscopic Observations of Polyacrylamide Structures

Polyacrylamide solutions have been used recently in Polyacrylamide solutions have been used recently in secondary recovery processes as mobility control agents. The literature presents several papers dealing with the behavior of these solutions in porous media and viscometers. Various investigators have presented theories describing the shapes and sizes of presented theories describing the shapes and sizes of polyacrylamides in water; however most of these polyacrylamides in water; however most of these investigators have based their conclusions on the measurement of apparent viscosities and resistance factors. But no one has made direct microscopic observations. This note is based upon results of microscopic studies' regarding the shape and size of Pusher 500* and Pusher 700* polyacrylamide polymer solutions after water had been evaporated. It was observed that the structures of these polymers are not linear but rather branched, and their shape and size can be modified by changing the pH or the NaCl concentration, or both. The structures observed have distances between their extremes several times greater than 0.45u; however, they can pass through filters of 0.45u. Fig. 1 shows portions of drops of Pusher 500 water-evaporated solutions as photographed through a conventional microscope. The pH of the solutions was 3.6, 8.0, and 10.8, reading from left to right. As can be seen from this figure, the shape of the polymer structures varies with the pH of the solution. The structures present more branches at an intermediate pH and larger, degraded structures at a low pH. This pH and larger, degraded structures at a low pH. This behavior explains the effect of pH on the apparent viscosities of polyacrylamide solutions as presented by Patton. Patton indicated that these solutions exhibit maximum apparent viscosities at intermediate pH. As we stated earlier, however, the structures of pH. As we stated earlier, however, the structures of polyacrylamides observed are more branched at this polyacrylamides observed are more branched at this pH. Consequently, the probability of interference pH. Consequently, the probability of interference between structures is greater, hence there is more resistance to flow. A photograph of a drop of Pusher 500 water-evaporated solution is shown in Fig. 2a. The pH of the solution was increased from an initial value of 3.6 to 10.6. It can be seen that branches regenerate; however, they seem to be larger than those shown in Fig. 1c, where the final pH was 10.6 but the initial pH was 8. This suggests that there is no permanent pH was 8. This suggests that there is no permanent change of structure of the Pusher 500 upon changing the Ph and that the original shapes can be nearly restored by changing the pH to its original value. The effect of NaCl in polyacrylamide solutions can be deduced from Fig. 2b. This figure shows a portion of a drop of 500 ppm water-evaporated solution of Pusher 500 with 0.1 percent NaCl and a pH of 8.0. Pusher 500 with 0.1 percent NaCl and a pH of 8.0. The structure shown in Fig. 2b is comparable with that of the low-ph pusher solution shown in Fig. la. This explains the behavior of ionizable polymers when there is an increase in NaCl concentration as reported by Mungan et al. The effect of filtration of polyacrylamide Pusher 500 solutions was studied by polyacrylamide Pusher 500 solutions was studied by passing the solution through filters of 0.45u. It was passing the solution through filters of 0.45u. It was observed that polymers having, certain structures were able to pass through these filters. Figs. lb and 2c are photographs of solutions of the same NaCl photographs of solutions of the same NaCl concentration and pH, before and after filtration, respectively. The structures are markedly similar. This suggest that they are highly flexible because they can pass through filters of 0.45u even when the maximum pass through filters of 0.45u even when the maximum distance between the extremes is several times greater than the openings in these filters. Microscopic observations on some nonionizable polymers indicate that their structures look like polymers indicate that their structures look like poly-acrylamides in the presence of NaCl or when the pH poly-acrylamides in the presence of NaCl or when the pH is low. P. 80

Studies of gamma dosimetry systems used for nuclear accident dosimetry.

For the past 5 years the Industrial Hygiene laboratory at Argonne National Laboratory has been charged with the responsibility for assessing gamma dose in the event of an inadvertent criticality. To fulfil this responsibility it has been necessary to study several commercially obtained dosimeters and to evaluate their performances under field conditions. The three systems studied were chemical dosimeters, polyacrylamide polymer solutions, and lithium fluoride dosimeters. Among the areas studied with these systems were response, stability, and ease of maintenance. The instrumentation involved in evaluation is, in general, conventional laboratory equipment with some modifications. The discussion of the chemical dosimeters encompasses three different packages and results of tests for accuracy and precision obtained with each are reported. The discussion of the polyacrylamide dosimeters mainly involves efforts to develop a stable and reproducible solution. Data obtained with gamma irradiation and X-rays are reported. The thermoluminescent detector used was LiF imbedded in teflon. The range of utility as well as results obtained with gamma irradiation are discussed. Finally, problems encountered with ambient backgrounds are discussed and attempts to eliminate this problem are evaluated.