Salinity Selection for a Low Salinity Water-Low Salinity Surfactant Process

A laboratory selection of salinity for a low salinity water-low salinity surfactant (LS-LSS) process is presented in this paper with systematical investigation on surfactant phase behavior, interfacial tension (IFT), and dynamic retention in porous media with IOS2024 and isoamyl alcohol (IAA) as surfactant system. The results show that 0.4 wt% IOS2024 with 1 wt% IAA can provide ultra-low IFT of 10^?3 mN/m at around 3000–4000 mg/L total dissolved solids, but at that salinity range the surfactant retention is very high. The search for an optimum surfactant formulation has to consider solution properties and retention in addition to the low IFT. The salinity for a LS-LSS process should thus not be focused on either optimal salinity or ultra-low IFT, but instead the best choice could be a compromise between the properties in question. The three-phase region, where ultra-low IFT are found, is also associated with high retention values. However, we show that as salinity is increased from a two-phase region with oil solubilized in a water continuous microemulsion, there is a region close to the three-phase boundary which has potential. This region does not give ultra-low, but fairly low (10^?2 mN/m in this case) interfacial tensions, and also significantly lower retention.      

Experimental Study of Microscopic Displacement Efficiency of Polymer Microspheres Using Low-Field NMR

For reservoirs in high water cut exploitation period, profile control and water plugging is one of the important ways to improve oil recovery. Cores with different permeability were flooded to analyze the displacement results and displacement mechanisms for different grain size of polymer microspheres. Fluid distribution in cores was measured by NMR spectroscopy after water flooding, polymer microspheres flooding, and subsequent water flooding. The range of pore sizes from which oil was swept out was also calculated. The results showed that microspheres can effectively sweep remaining oil in different pore size of the cores. The suitability of different grain size of polymer microspheres with cores is different, microspheres with micron size are suitable for high-permeability cores, and microspheres with nanometer size are suitable for low-permeability cores.     

Mechanistic Simulation Studies on Viscous-Elastic Polymer Flooding in Petroleum Reservoirs

Based on the theory and application developments of polymer flooding on enhancing oil recovery, an improved mathematical model has been developed to simulate the mechanism of viscous-elastic polymer flooding. IMPES method has been presented to solve the polymer flooding model considering the viscosifying effect of elasticity, the effect of decreasing residual oil and the degradation of polymer molecules. The validation of the model is approved by an experiment. A simulation example was carried out using the developed numerical simulator. The enhanced oil recovery mechanism was discussed for viscous-elastic polymer flooding, and corresponding influencing factors were also studied.     

Investigation on the Adaptability of the Polymer Microspheres for Fluid Flow Diversion in Porous Media

Large amounts of water producing from producers have been a great concern for petroleum engineers. In an attempt to inhibit water production and promote oil productivity, various water control agents and techniques have been devised for enhanced oil recovery purpose for decades with some good successes reported commercially. Mainly field-targeted specifically, however, these chemicals are limited in expansive reservoir applications for failing to tolerate harsh formation conditions of high temperature (HT) and high salinity (HS). Besides, their low injectivity is also another proper impediment. In this presentation, we synthesized a new agent of polymer microspheres using inverse emulsion polymerization technique to divert fluid patterns in deep porous media for reservoirs encountered recovery enhancement problems. These microspheres are made to tolerate HT and HS conditions, and can be pumped into deep pore space with relative ease. With the help of nuclear magnetic resonance (NMR) and nuclear pore membrane filtration techniques, a series of experimental procedures were conducted to test the adaptability of newly produced polymer microspheres to targeted pore structure in enhancing the sweeping efficiency of injection fluids. Both laboratory core tests and NMR data show good characteristics of polymer microspheres in modifying injection profile, demonstrating a good capability to divert fluid flow patterns in deep porous media and enhance oil productivity.     

Empirical Correlations for Viscosity of Polyacrylamide Solutions with the Effects of Salinity and Hardness

A series of experiments have been conducted to characterize and quantify the effects of shear rate, salinity, and hardness on the viscosity of polymer solutions. A set of correlations were developed to predict the viscosity of polymer solutions. These correlations consider the individual and combined effects of shear rate, salinity, and hardness on the viscosity of polymer solutions. The power-law model for the viscosity behavior has been modified to accommodate the influence caused by these three factors. Nonlinear regression was performed on the experimental data to develop the proposed correlations. The proposed correlations can be integrated into any reservoir simulator for polymer injection and should prove useful for the initial screening for the selection of the polymer for enhanced oil recovery applications in oil reservoirs.      

Effect of Gas-Wetness of Cores on Imbibition

Gas-wetness of cores plays an important role on imbibition. Gas-wetness of cores, treated by various concentration fluorocarbon polymer Zonyl8740 (aq), was measured by the captive bubble. Subsequently, co-current and counter-current spontaneous imbibition were conducted on the various gas-wet cores both in air/wate and air/oil systems. Experimental results showed that, with the increase of concentration of Zonyl8740 solutions, gas-wetting ability against liquid on the cores gets stronger, gas recovery decreases, and the trapped gas saturation increases. Meanwhile, on the cores treated by the same concentration Zonyl8740 solution, air/water systems have a stronger gas-wettability than that of air/oil systems.      

A Critical Review of the Role of Thin Liquid Films for Modified Salinity Brine Recovery Processes

Low salinity water injection (LSWI) is the process of injecting modified salinity brine with controlled ionic composition to achieve increased oil recovery compared to conventional waterflooding. This paper reviews the most recent advances in proposed low salinity mechanisms, but specifically emphasizes the role of thin liquid films in crude oil/brine/rock systems. Importantly, thin water films on rock surfaces affect hydraulic resistance of pore channels as well as phase-trapping mechanisms. As films become thicker, they provide greater lubrication of oil droplets and hence, flow resistance decreases. Consequently, films dictate oil and water distribution in porous media and determine the wettability of crude oil/brine/rock systems under static and dynamic conditions. The stability of the thin water films depends on the interactions between the oil/brine and the calcite/brine interfaces through van der Waals, electrostatic, and structural forces.     

The Wettability Alteration and the Effect of Initial Rock Wettability on Oil Recovery in Surfactant-based Enhanced Oil Recovery Processes

Wettablity alteration of rock surface is an important mechanism for surfactant-based enhanced oil recovery (EOR) processes. Two salt and temperature-tolerant surfactant formulations were developed based on the conditions of high temperature (97–120°C) and high salinity (20 × 10⁴ mg/L) reservoirs where a surfactant-based EOR process is attempted. Both the two sufactant formulations can achieve ultralow interfacial tension level (≤10^?3 mN/m) with crude oil after aging for 125 days at reservoir conditions. Wettability alteration of core slices induced by the two surfactant formulations was evalutated by measuring contact angles. Core flooding experiments were carried out to study the influence of initial rock wettabilities on oil recovery in the crude oil/surfactant/formation water/rock system. The results indicated that the two formulations could turn oil-wet core slices into water-wet at 90–120°C and 20 × 10⁴ mg/L salinity, while the water-wet core slices retained their hydrophilic nature. The core flooding experiments showed that the water-wet cores could yield higher oil recovery compared with the oil-wet cores in water flooding, surfactant, and subsequent water flooding process. The two surfactant formulations could successfully yield additional oil recovery in both oil-wet and water-wet cores.     

Influence of Hydrophobically Associating Polyacrylamide on Dispersion Property of Water-Soluble Phenol-For-maldehyde Resin

To improve dispersion stability of water soluble phenol-fomaldehyde resin (PFR) in relatively low salinity water, the effect of hydrophobically associating polymer (HAP) on the dispersion property of PFR in NaCl solution was studied by the measurement of the size and zeta potential of PFR, HAP, and PFR/HAP molecule aggregates in NaCl solution, and the turbidity of PFR and PFR/HAP dispersions. The results show that due to the hydrophobically group on HAP molecule has similar structure as molecular structure of PFR and stronger hydrophobically association of HAP molecules in NaCl solution, HAP, and PFR molecules can form complex molecule aggregates together. The formation of the complex molecule aggregates enhanced the stability of PFR dispersion in NaCl solution.     

Novel investigation based on cationic modified starch with residual anionic polymer for enhanced oil recovery

Cationic modified starch polymer (CMSP) is a newly developed green chemical agent designed to reutilize the residual anionic polymer found in reservoirs for enhanced oil recovery (EOR). In this study, a series of experiments were conducted to investigate the phase behavior of the residual anionic polymer, CMSP solution, and the flocculation generated from the mixture in plugging capacity and capability of enhancing oil recovery in heterogeneous reservoirs. The experiment results show that the phase behavior of the residual anionic polymer and CMSP solution could be divided into two parts: rapid flocculation reaction and dispersion reaction. The main mechanisms of the rapid flocculation reaction were charge neutralization and bridging. Based on the above results, an optimal amount of CMSP was chosen for plugging capacity, stability, and EOR study. Plugging tests in both parallel cores and EOR in three-layer heterogeneous square cores illustrate that the injected CMSP slug after polymer flooding can effectively block the high-permeability zone and initiate the remaining oil in middle- to low-permeability zones. The investigation results prove that the CMSP solution, injected after polymer flooding, reduces the pollution of produced fluid and further improves oil recovery.     

Mechanisms of Non-Newtonian Polymer Flow Through Porous Media Using Navier–Stokes Approach

This study includes solving non-Newtonian Navier–Stokes equation in three-dimensions (real rock images) and two-dimensions (simplified pore geometries) using the finite-difference method. The purpose of this study is to improve understanding of local phenomena leading to the mobilization of residual oil. This involves local pressure variations for non-Newtonian polymers and compares it with Newtonian fluid behavior. When a higher degree of shear thickening is induced, more flow diversion to side channels perpendicular to the main flow path and larger drag on fluids inside side channels will occur. This is consistent with oil mobilization and lowering of residual oil saturation.     

Empirical Correlations for Viscosity of Polyacrylamide Solutions with the Effects of Temperature and Shear Rate. II

Apparent viscosity measurements have been made to characterize the effects of shear rate and temperature on the partially hydrolyzed polyacrylamide solutions. The power-law model for the viscosity behavior has been modified to develop empirical correlations that combine effects of shear rate and temperature. Nonlinear regression was performed on the experimental data to develop the proposed correlation. The viscosities of the polymer solutions were measured in the temperature range of 25°C to 80°C, while the shear rate was varied from 1 to 1000 1/s. The proposed correlation should prove supportive for the preliminary selection of the polymers for enhanced oil recovery applications.     

低浓度HPAM/AlCit交联聚合物溶液性质研究

采用粘度法、扫描电镜（SEM）、核孔膜过滤、动态光散射（DLS）和27Al NMR法，研究了高分子量低浓度的部分水解聚丙烯酰胺（HPAM）与柠檬酸铝（AlCit）体系交联反应过程溶液性质变化.结果表明，HPAM与AlCit反应在低剪切速率时体系粘度随反应进行而降低，在剪切速率较高时具有剪切稠化现象，HPAM与AlCit反应过程中交联态Al的自旋 晶格弛豫时间随反应进行变短.低浓度的HPAM与AlCit发生分子内交联反应形成交联聚合物线团（LPC）在水中的分散体系，即交联聚合物溶液（LPS）.交联聚合物溶液中LPC的平均流体力学半径约为238 nm，其形态接近球形，具有多分散性. LPS对1.2 μm核孔膜的封堵程度与其反应时间有关.     

Organogelators and Polymer Crystallisation

The specific impact of low molecular weight organic gels on polymer crystallisation is examined. Conventional nucleating agents (NA) influence the polyolefins crystallisation and improve their mechanical properties, via an epitaxial mechanism. In the particular case where the pair NA/polymer form a gel at intermediate temperatures on cooling, optical properties (clarity) are significantly improved. This improvement is linked with the ability of organic gels to develop 3-D fibrillar network. The fibres morphology offers a large specific area, thus produces a high density of nuclei, homogeneously dispersed. Gelling organic molecules are certainly a promising route towards the design of efficient additives in polymer processing.     

Emulsion procedures for thermally reversible covalent crosslinking of polymers

Quaternization and dequaternization of tertiary amine compounds were employed to obtain thermally reversible ionene networks from aqueous colloidal polymer dispersions prepared via emulsion polymerization. Chlorine‐functionalized polymers prepared via the emulsion copolymerization of styrene (St), butylacrylate (BA), or both with chloromethylstyrene, and amino‐functionalized polymers prepared via the emulsion copolymerization of St, BA, or both with 2‐(dimethylamino)ethylacrylate or 4‐vinylpyridine, were reacted without polymer separation, with a ditertiaryamine crosslinker and a dihalide crosslinker, respectively, to obtain crosslinked polymers. Crosslinked polymers were also obtained via the reaction of a chlorine‐functionalized polymer dispersion with an amino‐functionalized polymer dispersion or via the drying of the polymer blend prepared from the two kinds of dispersions. Reactive solubility experiments, flowability investigations (by thermocompression at ca. 215 °C), IR, and ¹H NMR analyses of the obtained crosslinked polymers indicated that the generated ionene bridges dequaternized on heating and requaternized on cooling. In comparison with solution crosslinking, no organic solvent was employed, and simple procedures were required for the preparation of the thermally reversible covalent crosslinked polymers. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 4373–4384, 2000     

Polymer Zwitterions for Stabilization of CsPbBr3 Perovskite Nanoparticles and Nanocomposite Films

Functional polymers with sulfobetaine or phosphorylcholine zwitterions as pendent groups are demonstrated as both ligands and host matrices for CsPbBr₃ perovskite nanoparticles (PNPs). These polymers produce nanocomposite films with excellent NP dispersion, optical transparency, and impressive resistance to NP degradation upon exposure to water. Multidentate interactions of the zwitterion‐containing copolymers with the PNPs induce dispersed or weakly aggregated nanocomposite morphologies, depending on the extent of zwitterionic functionality in the polymer. Incorporating additional functionality into the polymers, such as benzophenone pendent groups, yields lithographically patternable films, while time‐resolved photoluminescence measurements provide insight into the electronic impact of PNPs in zwitterionic polymer matrices.     

全氟丙烯酸酯聚合物乳液研究进展

全氟丙烯酸酯聚合物乳液由于具有优异的表面特性，耐候性及环境友好性，可望在建筑涂料、纺织工业以及其它重要领域得到广泛的应用。本文综述了全氟丙烯酸酯聚合物的特性及乳液的合成方法与应用，介绍了国内外在此领域的研究状况。     

耐温抗盐驱油聚合物溶液黏弹性

对3种不同结构类型的耐温抗盐驱油聚合物〔高分子量聚丙烯酰胺(HPAM)、磺化聚丙烯酰胺(S-HPAM)和疏水缔合聚丙烯酰胺(A-HPAM)〕的溶液黏弹性能进行了研究。在温度85℃下,通过稳态剪切和动态剪切试验,考察了质量浓度和矿化度对聚合物溶液黏弹性的影响。结果表明,随剪切速率增加,溶液表观黏度逐渐降低。质量浓度越高,溶液的储能模量(G')和损耗模量(G″)越大。由动态剪切实验数据,计算得到第一法向应力差(N1)。随质量浓度增加,聚合物溶液的N1逐渐增大;随矿化度增加,聚合物溶液的N1出现不同盐敏感区域,说明不同结构类型的驱油聚合物溶液对矿化度的弹性响应不同。研究结果为高温高盐油藏聚合物驱剂的选择及开发提供了理论参考。     

超临界CO2在高分子合成与制备中的应用

介绍超临界二氧化碳流体作为介质在高分子合成与制备中的研究进展。文中表明，可在超临界二氧化碳中实施氟代单体的自由基溶液聚合、甲基丙烯酸甲酯的分散聚合、丙烯酸的沉淀聚合、丙烯酰胺的反相乳液聚合以及异丁基乙烯基醚的阳离子聚合等多种聚合反应，可用超临界二氧化碳溶胀聚合法制备梯度共混物。此外，超临界二氧化碳还可用于聚合物分级和聚合物微孔、微纤与微球材料的制备等，显示出超临界二氧化碳是一种对环境无污染且价廉的