A study of the properties of hydrophobically associating water-soluble polymers used in drilling fluids

Hydrophobically associating water-soluble polymers (HPAP) have been synthesized from acrylamide(AM), acrylate (AA), 2-acrylamido-2-methyl propane sulfonic acid (AMPS) and hydrophobic monomer (AP) in aqueous solution by radical polymerization. New polymer drilling fluids are made up of HPAP, which is used as viscosifiers and encapsulation agents. Properties of this system are reported in this paper. Results indicate that this system has a high value of yield point to plastic viscosity (YP/PV≥0.7), high viscosity at a low-shear rate (LSRV≥30000mPa·s), excellent shear thinning behavior, good solid-carrying behavior, resistance to shear, good thermal stability (as high as 140℃) and salt resistance. The system has excellent behavior in high-density solution of NaCl and in calcium and magnesium rich saline solutions. Hence, HPAP also can be used in saltwater polymer drilling fluids.

SYNTHESIS AND CHARACTERIZATION OF A NOVEL FLUORINE-CONTAINING HYDROPHOBICALLY ASSOCIATING POLYMER

In this article, the synthesis and characterization of a novel fluoromonomer and its copolymer with acrylamide is reported. 2-perfluoroamyl-4-hydroxylquinoline 2 was synthesized from ethyl 2, 2-dihydroperfluoroheptanoate in high yields. The monomer 4 was then synthesized from 2 in two steps readily in high yields. Synthesis and characterization of copolymers of acrylamide (AM) and the fluoromonomer were investigated. The composition and intrinsic viscosity of these copolymers were studied. It was found that the rheological properties of aqueous solutions of polyacrylamide were modified significantly when a small proportion of the fluoromonomer 4 was incorporated on investigating the viscosity-concentration profiles, pseudoplasticity of these solutions and the effect of the presence of surfactant. These results could be explained by the hydrophobic association of the fluorocarbon segments in the aqueous solutions of these copolymers.

Synthesis and Solution Properties of Hydrophobic Associating Polymers

Acrylamide/2-acrylamido alkane sulfonic acid hydrophobic associating copolymers were synthesized by micellar copolymerization. Effects of hydrophobe content, polymer concentration, salinity and surfactant on rheological behavior of copolymers were investigated and the conformation of polymers in solution was studied by means of environmental scanning electronic microscopy and dynamic light scattering. The experimental results showed that in the dilute regime the hydrophobic parts could interact intramolecularly, while in the regime where the polymer concentration was higher than the critical association concentration, intermolecular hydrophobic association became predominant. Within the limit of the solubility, the critical association concentration of the polymer decreased with the increase of the salinity. The experimental results of the solution conformation indicated the presence of the three-dimensional network structure in deionized water and the size of the mesh in the network varied with the polymer concentration. In NaCl solution, above the critical association concentration, an increase in polymer concentration enhanced the intermolecular association and also enlarged the hydrodynamic radius. It would result in the improvement of the thickening power of polymers.

The effect of betaine surfactants on the association behavior of associating polymer

The interfacial properties and rheological behavior of surfactant/polymer complex systems were measured to investigate the association behavior of the associating polymer.Compared with the pure surfactant solution,there are two inflection points in the surface tension curve for the surfactant/polymer complex systems.The two inflection points are dependent on the surfactant type and polymer concentration.The effect of surfactant on the rheological behavior of polymer can be divided into two aspects.First,the addition of short-chain betaine surfactant is detrimental to the viscosity of polymer solution due to the electrostatic shielding effect.Second,long-chain betaine surfactant also reduces the viscosity of polymer solutions at low concentrations.However,when the concentration of the long-chain betaine surfactant is relatively high,the long-chain betaine surfactant could form worm-like micelles that promote the intermolecular association and thus increase the number of associating junctions,thereby resulting in the augmentation of viscosity.So it is necessary to apply the long-chain betaine surfactant to build the polymer/surfactant flooding system.The interaction model between surfactant and polymer is proposed,which is different from the traditional‘Three-Region Model’.

Study and Application of a New Association Polymer System for Profile Control

A new polymer system, referred to simply as the AP-P4 polymer system, aims at solving the problems of high temperature, high salinity and the poor shearing resistance, all of which are encountered by conventional polymers (such as polyacrylamide) used in profile control, profile performance improvement and EOR operations in the Zhongyuan Oilfield, Sinopec. This system has been developed on the basis of the specific molecular structure and the better properties of high temperature resistance, high salinity resistance and strong shearing resistance of the new type of AP-P4 association polymer. Acidity modifying agents and cross-linking agents (MZ-YL, MZ-BE, MZ-XS), compatible with the new polymer system, are selected. Results of performance tests have shown that the new polymer system has excellent thickening, high temperature, high salinity and shearing resistance and anti-dehydrating properties. In 2003, it underwent its first pilot test in 26 wells in China, with remarkable effects in increasing oil production and decreasing water production. The newly developed polymer system and its application technology described in this paper may play a guiding role in polymer profile control operations in the oil reservoirs of high temperature and high salinity.

STUDIES ON SELF-ASSOCIATIVE BEHAVIOR OF A NOVEL CATION AMPHIPHILIC POLYMER

A novel associating polymer P(AEBA) was synthesized by radical polymerization of the cationic amphiphilic monomer,4-(2-(acryloyloxy)ethoxy)benzyl tri-ethyl ammonium bromide(AEBA),in aqueous solutions.P(AEBA) displays a strong tendency for self-association in aqueous solutions and is sensitive to the external stimulation such as added salt.The associative properties and morphologies of P(AEBA) were studied by fluorescnece probe technique,viscometry and TEM.In dilute salt-free solutions P(AEBA) behaves as pol...

ASSOCIATION OF ETHYLENE VINYL ACETATE COPOLYMER IN DILUTE SOLUTIONS IV. SOLVENT MIXTURE AND ADDITIVE EFFECT ON C_A

Critical association concentration (Ca) of ethylene-vinyl acetate copolymer (EVA) in selective solvent mixtures of 1,2-dichloroethane (DCE) (polar solvent) and cyclohexane (CYH) (non-polar solvent) was investigated. DCE is a good solvent for polyvinyl acetate (PVAc) and a poor solvent for paraffin, whereas CYH is a good solvent for the paraffin and a precipitant for PVAc. Viscosities of EVA in different compositions of the solvent mixture with and without additives were measured. Viscosity results were used to determine the C-A value of the systems. It is shown that C-A was markedly dependent on the composition of the solvent mixture and concentration and structure of the additive. Solvation and competition between hydrogen bonding and micellisation were suggested for qualitative description of the changing of C-A value observed.

Study on the Ion Association in PVdF-based Gel Polymer Electrolyte

Gel polymer electrolytes based on the poly （vinylidene fluoride） （PVdF） and the electrolyte of LiClO4 in propylene carbonate （PC） were prepared by the solution casting technique. The ionic conductivity of the gel electrolytes was above 10^-3 S ·cm^-1 at 30℃ and was affected by the concentration of lithium salt. Because of the strong coulombiq attractions, the dissolved salt ions might aggregate into ion pairs and multiple ion aggregates. The analysis of DSC and X-ray diffraction revealed that the ions association occurred at higher concentration of lithium salt.

Rheological Properties of Hydrophobically Associating Polyacrylamide Solution

A temperature-resistant, salt-tolerant polyacrylamide, hydrophobically associating polymer （HAP）, was synthesized in the State Key Laboratory of Heavy Oil Processing. The rheological behavior of HAP solution was investigated by means of flow experiments in porous media and by using a HAAKE RS600 rheometer. The results of Nuclepore membrane filtration showed that filtration time increased sharply when the critical association concentration was reached. Shear rate had a greater impact on viscosity and shear stress with increasing HAP concentration. The HAP solution with a concentration of 100 mg/L （salinity 32,868 mg/L） exhibited negative thixotropy. However, at the same salinity the HAP solution showed thixotropy and its viscosity became greater when the polymer concentration increased to 1,500 mg/L. The flow experiments in cemented core samples indicated that the resistance factor and residual resistance factor of the HAP solution were 31.8 and 12 when polymer concentration and salinity were 1,500 mg/L, 32,868 mg/L at 85℃ respectively, which is favorable for flooding application. Such factors of partially hydrolyzed polyaerylamide 3530S were merely 3.14 and 1.71, so it could not be applied to polymer flooding in the oilfield with high temperature and high salinity.

Viscoelastic rheological property of different types of polymer solutions for enhanced oil recovery

The capability of hydrophobic association polymer(HAPAM) to displace oil is different from that of hydrolyzed polyacrylamide(HPAM) because they have different rheological properties.The viscoelasticity of five polymers was measured using Physica MCR301 rheometer and was compared.The five polymers include three HAPAMs with relative molecular mass of 1 248×104(TypeⅠ),750×104(TypeⅡ),and 571×104(Type Ⅲ) separately and two HPAMs with relative molecular mass of 1 200×104 and 3 800×104 respectively.The experiment results indicate that the viscoelasticity of HAPAM is better than that of HPAM.The storage modulus G' and the loss modulus G″ for HAPAM solutions are also larger than those for HPAM.Comparing the rheological curves of different HAPAM types,it is found that the viscosity of typeⅡ and type Ⅲ is almost same at different shear rates while the viscosity of type I is the lower than that of Types Ⅱ and Ⅲ.The storage modulus G' and the loss modulus G″ for three types of HAPAM were measured in low oscillation frequency range,and the results show that G' is greater than G″ for all three different types of HAPAM,but their loss modulus is almost same,and the G' is in the order of type Ⅱ>type Ⅲ>type I.In addition,the G' and G″ increase with aging time for all three HAPAM solutions were stayed at different days.The viscoelasticity of type Ⅰ reaches the highest value when aging time is 9 d at 45 ℃,but it is 7 d for type Ⅱ and type Ⅲ.The different viscoelasticity properties can be attributed to self-organization supermolecule networks which is formed by hydrophobic association of HAPAM molecular and molecular chain entanglement.

A NOVEL INTERPRETATION OF CONCENTRATION DEPENDENCE OF VISCOSITY OF DILUTE POLYMER SOLUTION

The concentration dependence of the reduced viscosity of dilute polymer solution is interpreted in the light of a new concept of the self-association of polymer chains in dilute solution. The apparent self-association constant is defined as the molar association constant divided by the molar mass of individual polymer chain and is numerically interconvertible with the Huggins coefficient. The molar association constant is directly proportional to the effective hydrodynamic volume of the polymer chain in solution and is irrespective of the chain architecture. The effective hydrodynamic volume accounts for the non-spherical conformation of a short polymer chain in solution and is a product of a shape factor and hydrodynamic volume. The observed enhancement of Huggins coefficient for short chain and branched polymer is satisfactorily interpreted by the concept of self-association. The concept of self-association allows us to predict the existence of a boundary concentration C-s(dynamic contact concentration) which divides the dilute polymer solution into two regions.

Template Effect of Hydrophobically Associating Polymers on the Construction of Cuprous Oxide Micro Structure

To determine the template effect of hydrophobically associating copolymers（HACPs） on the morphology of nano/micro structures, six HACPs were synthesized and used as templates to biomimetically synthesize cuprous oxide（Cu2O）, an important semiconductor. This experiment showed a clear relationship between the associating state of the HACP molecules and the morphology of the Cu2O particles. Cu2O hollow spheres were preferentially prepared when the HACP molecules were in an intramolecular associating state. Furthermore, a Cu2O hexapod was easily obtained when the HACP molecules were in an intermolecular associating state. The morphologies of the Cu2O crystals prepared in the presence of the HACPs also confirmed this result.

Stress-Structure Relationship of the Reversible Associating Polymer Network under Start-up Shear Flow

We adopt Langevin dynamics to explore the stress-structure relationship of telechelic reversible associating polymer gel during startup shear flow, with shear strengths varying from Wi=12.6 to Wi=12640. At weak shear flow Wi=12.6, the shear stress proportionally increases with shear strain at short times, followed by a strain hardening behavior and then passes through a maximum(σmax, γmax) and finally decreases until it reaches the steady state. During the evolution of stress, the gel network is only slightly broken and essentially maintains its framework, and the strain hardening behavior originates from the excessive stretching of chains. On the other hand, the stress-strain curve at intermediate shear flow Wi=505.6 shows two differences from that at Wi=12.6, namely, the absence of strain hardening and a dramatic increase of stress at large strains,which is caused by the rupture of gel network at small strains and the network recovery at large strains, respectively. Finally, at very strong shear flow Wi=6319.7, the gel network is immediately broken by shear flow and the stress-strain curve exhibits similar behaviors to those of classical polymeric liquids.

Synthesis of Amphiphilic Polyelectrolyte and Study of Their Association Behavior in Hydroalcoholic Media

The objective of the work involves the synthesis of comb-like amphiphilic cationic polymers with repeating units methacylamides laterally substituted by a group containing a quaternary ammonium site and a hydrophobic n-alkyl side chain with 8-10 carbon atoms. Two synthesis methods were developed successfully. The first method is consisted to synthesizing first amphiphilic cationic methacrylamide monomers. In the second method the tertiary amine groups of polymers precursors were quaternised with various n-alkyl bromides. All the polymers obtained in this way were characterized by spectroscopic methods： 1^H NMR and by viscometry. The reduced viscosity of hydro-alcoholic polymer solution decreases with polymer concentration. Viscometry study showed that these polymers display typical polysoap behavior in hydro-alcoholic mixtures.

井地过渡带对聚合物驱油剂性能影响研究

利用井地过渡带剪切模拟实验装置,以疏水缔合聚合物AP-P4为研究对象,研究不同吸水强度条件下,剪切后聚合物溶液的表观黏度、流变性、阻力和残余阻力系数、微观结构以及水动力学半径的变化情况。结果表明,经井地过渡带剪切后,随着吸水强度的增大,聚合物AP-P4溶液的黏度损失率高达61.4%,建立阻力系数和残余阻力系数的能力降低40.0%以上,但其建立残余阻力系数能力的降低幅度要比建立阻力系数能力的降低幅度小。聚合物溶液的储能模量和损耗模量降低,微观结构被破坏的越严重,水动力学半径越小。

疏水缔合聚合物乳化性能及分相特征

配制了不同的疏水缔合聚合物(HAP),分析了HAP含量、疏水单体含量和油相含量对于聚合物乳化性能的影响,探讨了连续相中疏水缔合结构与油滴的相互作用规律。实验结果表明,HAP乳化时,油滴与连续相中的缔合结构相互作用,形成新的分子链间网络节点,构成了新的三维网络结构,使乳状液增黏。HAP的乳化增黏幅度由连续相与分散相的性质共同决定,其中,HP-1乳状液表观黏度最高增幅为36%。随着HAP中疏水单体含量的增加,乳化增黏幅度逐渐上升;HAP含量一定时,随油相含量增大,HAP乳状液乳化增黏幅度先增大后稳定、稳定性增强,但富集相体积存在最大值。HAP乳化性能及分相特征取决于连续相中的疏水缔合结构与油滴相互作用。

一种全温域聚合物缓凝剂

针对传统链状聚合物缓凝剂规律性差、中低温易超缓凝、强度发展缓慢的技术难题,根据缓凝剂作用机理、通过优化分子结构设计,在2-丙烯酰胺-2-甲基丙磺酸(AMPS)和衣康酸(IA)基础上引入苯乙烯磺酸钠(SSS)单体和长链疏水缔合单体TAS-24,制备出一种新型四元聚合物缓凝剂C-R45L,并通过红外光谱和水泥浆性能评价对其进行了研究。研究结果表明:缓凝剂C-R45L具有良好的缓凝效果,在加量为4%、温度为210℃的下稠化时间可达到347 min;在高温及中低温下都具有良好的规律性,不仅适用于高温条件,也可应用于中低温固井;对水泥石抗压强度无不利影响,中低温及顶部强度发展快,具有良好的大温差性能,适用于长封固段固井。缓凝剂C-R45L在古探1井成功应用,固井质量优良。

一种具有超长侧链的疏水缔合型聚合物的合成及减阻性能评价

采用曲拉通和丙烯酰氯醇解合成一种水溶性可聚合单体,仅使用水作为溶剂合成一种具有超长侧链的疏水缔合型聚丙烯酰胺(HAPAM)作为减阻剂,通过分子动力学模拟方法对比了聚丙烯酰胺、部分水解聚丙烯酰胺和合成的具有超长侧链的HAPAM与水的相互作用,并分别以去离子水和盐水配液改变HAPAM含量,测量不同HAPAM含量的滑溜水在不同流速下的摩阻,并计算相应的减阻率。实验结果表明,具有超长侧链的HAPAM与水的相互作用最强;减阻率随流速的增加而增大,HAPAM含量越高,减阻率达到70%所需的流速越高,减阻率最高可达80%以上;盐对滑溜水的减阻率和黏度有显著负面影响,需提高HAPAM含量才能获得理想的减阻率;SEM表征结果显示,HAPAM在清水和盐水中的分布形态均为网状结构。