疏水缔合聚丙烯酰胺渗流阻力特征研究

疏水缔合聚丙烯酰胺(HAP)通过缔合作用在溶液中形成聚集形态,表现出了特殊的溶液性能。通过在HPAM溶液中加入钠土分散体系,使HPAM絮凝体系具有类似HAP溶液的聚集形态,分析两种体系在多孔介质中的渗流特征,研究疏水缔合聚丙烯酰胺溶液建立渗流阻力的方式。结果表明,HPAM絮凝体系在多孔介质中,主要依靠吸附滞留作用建立流动阻力;钠土形成的聚集结构在较低渗透率的多孔介质中存在注入压力高的问题。而疏水缔合聚丙烯酰胺依靠溶液中分子间缔合作用,形成了超分子聚集体,在多孔介质流动过程中,超分子聚集体结构发生变化。在较低渗透率多孔介质中,形成的聚集体结构破坏作用较强,使其粘度下降幅度较大,保证了聚合物溶液仍具有较好的注入性。而在高渗透多孔介质中仍具有较高的粘度,并能够建立较高的阻力系数和残余阻力系数。由此表明,疏水缔合聚丙烯酰胺溶液形成的聚集体结构在多孔介质中仍具有可逆性,在多孔介质剪切作用下,仍能形成聚合物分子之间以及与岩石之间的相互作用,使其能够建立较高的流动阻力。     

聚合物水溶液流经岩心后残余阻力系数预测数学模型

聚合物溶液的残余阻力系数是指当其通过多孔介质时,因为滞留或堵塞造成多孔介质对水渗透率下降的度量。残余阻力系数越大,油层渗透率下降就越大,如果残余阻力系数过大,就会造成油层的阻塞,不利于聚合物驱。通过推导数学公式以及开展流动实验等,对于聚合物溶液流经岩心后的残余阻力系数进行了预测,对于在驱油过程中聚合物的选取有一定的指导意义。     

岩心中粘土含量对聚合物滞留与捕集的影响

聚合物在流经多孔介质的过程中,由于表面吸附、机械捕集、水动力学捕集和聚合物分子间的相互作用而产生滞留,影响驱油效果。本文通过物质平衡法测得了张家口不同粘土含量的岩心中聚丙烯酰胺的滞留量与捕集量,分析了岩心中的粘土含量对聚合物滞留与捕集的影响,并得出了吸附量、滞留量与捕集量的关系。     

交联聚合物溶液突破性能

交联聚合物溶液（LPS）是由低浓度部分水解聚丙稀酰胺和交联剂柠檬酸铝形成的交联聚合物线团（LPC）在水中的分散体系。采用毛玻璃模型驱油实验和核孔膜过滤实验研究了LPS的突破性能以及再封堵特性。实验结果表明,LPS在多孔介质吸附滞留封堵后可以产生突破,突破后还具有再次封堵特性,能够起到更好的深部调剖效果;LPS封堵后突破压力与封堵强度有关,在缓慢升压的情况下,LPC不断的滞留、聚集,形成‘滤饼’,封堵强度越来越大,需要很高的压力才能够使封堵的LPC克服LPC与多孔介质的吸附力以及LPC分子间力产生突破,在封堵强度较低的情况下必须有一个较高的冲击力才能使封堵的LPC发生突破;形成LPS聚合物相对分子质量越高或者封堵的多孔介质孔径越小则其突破压力越大。     

聚合物驱对储层及其自身性质影响实验研究

目前聚合物驱油技术已成为各大油田提高采收率的主要手段。聚合物溶液在多孔介质中流动过程中，由于其吸附、滞留特性对油层的渗透率、孔隙结构、油水流动特性有一定的影响，聚合物溶液的粘度也会发生变化。通过实验研究，聚合物驱后储层渗透率降低，储层粒度越小渗透率下降程度越大，孔隙度没有明显的变化，聚合物的吸附降低了水溶液和油溶液的渗透率。在高渗的储层中，聚合物吸附对油溶液流动几乎没有影响。储层粒度越小，渗透率越小，聚合物粘度降低的程度越大。     

交联聚合物溶液在孔隙介质中的流动与滞留行为

在内径为40 mm、长度为1500 mm的填充砂管中,在线测量了由部分水解聚丙烯酰胺和柠檬酸铝所形成的交联聚合物溶液在填充砂孔隙介质中的流动和滞留特性,考察了交联聚合物溶液的流动形态及流动速度对孔隙封堵位置的影响。结果表明,交联聚合物溶液在孔隙介质中的流动过程中,经过多次压力脉动最终导致一种局部性的非均匀封堵;随着流动线速度的增加,封堵位置与交联聚合物注入口间的距离呈非线性增大;对应于封堵现象的发生,可能存在一个临界注入量,只有当交联聚合物溶液的注入量大于该临界值时,才会对孔隙介质产生封堵作用。     

聚合物溶液在波纹管中的流动特性

本文研究了聚合物驱中聚合物溶液流动的现状、多孔介质模型、粘弹性流体模型,波纹管模型的状况。选择适当的粘弹流体模型,简化油藏多孔介质模型,波纹管模型,建立了由连续方程,运动方程和上随体Maxwell本构方程,流函数,涡量函数及边界条件组成的较完整的数学模型。得到了在波纹管条件下的流函数场,速度场,应力场。其结果与文献中所做的图形对比发现结果吻合的较好,为在理论上研究粘弹性聚合物溶液的驱油机理做出帮助。     

新型pH敏感性聚合物调驱研究综述

pH敏感性聚合物是一种新型的聚合物调驱体系,其重要特点是聚合物分子结构对溶液pH的敏感性。在酸性条件下,聚合物分子卷曲,溶液黏度低,注入性能好;当酸进入地层与储层岩石发生反应后,pH值升高,聚合物溶液黏度增加,有效封堵高渗层,达到流度控制的目的。在调研国外pH敏感性聚合物调驱研究现状的基础上,介绍了聚合物的pH敏感特性,总结了矿化度、聚合物质量浓度等因素对pH敏感性聚合物流变特征的影响,并分析了低pH聚合物体系在多孔介质中的运移性能,证实pH敏感性聚合物能够提高注入能力,在油藏深部调剖和流度控制中效果良好,有广阔的应用前景。     

多孔介质中不同缔合能聚合物的吸附滞留研究

以疏水基含量分别为0.35%和0.2%的疏水缔合聚合物和常规线性聚丙烯酰胺为对象,研究聚合物缔合能力对吸附滞留特征的影响。采用浸泡法研究了不同浓度聚合物在石英砂上的静态吸附特征,并采用流动实验装置测定了浓度为1 500 mg/L的三种聚合物在不同速度下的动态滞留量。结果表明,疏水缔合聚合物呈现三段式的静态吸附特征,即先缓慢上升,达到临界缔合浓度后快速上升,最后趋于平稳;缔合能力越强,在临界缔合浓度之后的上升段幅度越大;缔合能力强的聚合物HAWP-0.35能够在3 mL/min的注入速度下与HPAM在0.5 mL/min具有相当的吸附滞留量,表明缔合能力能够克服注入速度对聚合物在多孔介质中动态滞留量的影响,缔合能力越强,吸附滞留量越大     

多孔介质中不同缔合能聚合物的吸附滞留研究

以疏水基含量分别为0.35%和0.2%的疏水缔合聚合物和常规线性聚丙烯酰胺为对象,研究聚合物缔合能力对吸附滞留特征的影响。采用浸泡法研究了不同浓度聚合物在石英砂上的静态吸附特征,并采用流动实验装置测定了浓度为1 500 mg/L的三种聚合物在不同速度下的动态滞留量。结果表明,疏水缔合聚合物呈现三段式的静态吸附特征,即先缓慢上升,达到临界缔合浓度后快速上升,最后趋于平稳;缔合能力越强,在临界缔合浓度之后的上升段幅度越大;缔合能力强的聚合物HAWP-0.35能够在3 mL/min的注入速度下与HPAM在0.5 mL/min具有相当的吸附滞留量,表明缔合能力能够克服注入速度对聚合物在多孔介质中动态滞留量的影响,缔合能力越强,吸附滞留量越大     

Rheological behavior of hydrolyzed polyacrylamide solution flowing through a molecular weight adjusting device with porous medium☆

The separate-layer injection in different interlayers and the injection of the same-molecular-weight polymer solution in a layer are necessary in the polymer flooding process because of heterogeneous multilayer sandstone reservoirs in EOR projects.To alleviate the matching problems between the layer permeability and the injected polymer molecular weight,a molecular weight adjusting device with porous medium was designed on the basis of mechanical degradation principle.In terms of four variables(polymer concentration,pore diameter,length of shear component and flow rate),the rheological behavior of hydrolyzed polyacrylamide(HPAM)solution flowing through the device was investigated in detail.The change of these variables is able to control the shear rate of HPAM solutions through ceramic foam,and achieve the desired degree of shear degradation and the final rheological parameters—viscosity loss,viscoelasticity and pressure drop.Therefore,a linear relationship between viscosity loss and shearing rate was established so as to obtain the targeted viscosity easily.Field tests in the Daqing Oil Field showed that the polymer molecular weight could drop 20%to 50%.In a word,the results could guide the industrial application of the novel device and the further study of polymer degradation flowing through the porous medium.     

Non-equilibrium chemical potential and polymer extraction from a porous matrix

The influence of a flow on the transfer of a polymer solution from a porous matrix to a flowing fluid is analysed. Since the flow modifies the free energy of the solution, through stretching and orientation of the macromolecules, the thermodynamic driving force for polymer transport is modified with respect to that of a quiescent fluid. The consequences of this modification for the extraction of a polymer from a porous matrix are explored in detail, and the formal results are explicitly illustrated by means of a specific solution. For the particular example analysed here, of possible interest in oil extraction or in microfluidic problems, the non-equilibrium effects may yield a reduction of the order of 10% of the extraction rate.     

Water slug injection containing n polymers in porous media

Injection of water containing dissolved chemicals is an efficient oil recovery technique. One of the problems of this method is the loss of the chemical components due to interactions between rock and fluid. In polymer injection, adsorption may happen and lead to low process efficiency. The interaction between rock and fluid is governed by the adsorption isotherm, which relates the polymer concentration in water with the adsorbed amount on the rock. In this paper the problem of oil displacement by a water slug containing n chemical components that may be adsorbed is analyzed. The system of conservation laws is solved and the structure of the solution for the case of Henry's adsorption isotherm is completely described. The concentration profile of each component and the chromatographic cycle is calculated through simple expressions. The complete and detailed solution for the case of slug injection containing three chemical components is presented. The general solution developed can be used to model several Enhanced Oil Recovery techniques, in which the chemical components adsorb in porous media following Henry's adsorption isotherm.     

A study on the determination of in-plane permeability of fiber preforms

One of the parameters most frequently used in modeling and designing the mold filling process is the permeability of fibrous preforms. To obtain radial propagation of a viscous polymer into a homogeneous orthotropic porous medium, an approximate solution is derived and its results are compared with numerical ones obtained from boundary element method (BEM). A simple and direct procedure incorporating approximate solution with experimental data has been proposed to determine the principal in-plane permeabilities of the reinforcements. A scheme is also suggested in order to increase the accuracy in the determination of degree of anisotropy. The effect of resin injection type on permeability is investigated through the experiments.     

Solution blow spinning: A new method to produce micro‐ and nanofibers from polymer solutions

A solution blow spinning technique was developed using elements of both electrospinning and melt blowing technologies as an alternative method for making non‐woven webs of micro‐ and nanofibers with diameters comparable with those made by the electrospinning process with the advantage of having a fiber production rate (measured by the polymer injection rate) several times higher. The diameters of fibers produced ranged from 40 nm for poly(lactic acid) to several micrometers for poly(methyl methacrylate). This solution blow spinning method uses a syringe pump to deliver a polymer solution to an apparatus consisting of concentric nozzles whereby the polymer solution is pumped through the inner nozzle while a constant, high velocity gas flow is sustained through the outer nozzle. Analysis of the process showed that pressure difference and shearing at the gas/solution interface jettisoned multiple strands of polymer solution towards a collector. During flight, the solvent component of the strands rapidly evaporates forming a web of micro and nanofibers. The effect of injection rate, gas flow pressure, polymer concentration, working distance, and protrusion distance of the inner nozzle was investigated. Polymer type and concentration had a greater effect on fiber diameter than the other parameters tested. Injection rate, gas flow pressure, and working distance affected fiber production rate and/or fiber morphology. Fibers were easily formed into yarns of micro‐ and nanofibers or non‐woven films that could be applied directly onto biological tissue or collected in sheets on a rotating drum. Indeed, virtually any type of target could be used for fiber collection. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

The performance of polymer solutions in enhanced oil recovery: studies on their rheological,interfacial, and porous media behaviors

Four polymeric solutions based on xanthan, high and low molecular weight sulfonated polyacrylamides, and hydrolyzed polyacrylamide were prepared in aqueous solutions and their behaviors in enhanced oil recovery applications were investigated. The effect of thermal aging on polymer solutions was evaluated through rheological measurement. Pendant drop method was also used for measuring the interfacial tension (IFT) between crude oil and brine containing different polymer solutions. Moreover, the zeta potential of the oil reservoir particles treated with oil and polymer was determined by electrophoresis method in a nano-zeta meter instrument. In addition, sand pack and core flooding setup were used for evaluating the effectiveness of the polymer solutions in porous media. Polymer solutions displayed non-Newtonian behavior in almost the whole range of the shear rate applied; a shear thinning behavior was seen. Furthermore, the aging of polymers in formation water decreased the shear viscosity of all the polymers. The oil/water IFT decreased by the addition of polymers to water. The effect of xanthan polymer on zeta potential value was greater than that of the three acrylamide-based polymers. According to sand pack tests, by increasing the polymer concentration, the incremental oil recovery initially increased up to a polymer concentration of 3,500 ppm and then started to fall. Recovery factor increased from 50 to 65 % using the polymer solution in core flooding experiments. By increasing the injection rate from 0.2 to 3 mL/min, the injected fluid had less time to sweep the pores and consequently the amount of recovered oil decreased.     

Immobilization of cellulase using porous polymer matrix

A new method is discussed for the immobilization of cellulase using porous polymer matrices, which were obtained by radiation polymerization of hydrophilic monomers. In this method, the immobilized enzyme matrix was prepared by enzyme absorbtion in the porous polymer matrix and drying treatment. The enzyme activity of the immobilized enzyme matrix varied with monomer concentration, cooling rate of the monomer solution, and hydrophilicity of the polymer matrix, taking the change of the nature of the porous structure in the polymer matrix. The leakage of the enzymes from the polymer matrix was not observed in the repeated batch enzyme reactions.     

Flow-induced degradation of hydrolyzed polyacrylamide in porous media

Summary In this work we present an experimental study of flow-induced degradation of hydrolyzed polyacrylamide in aqueous solutions flowing through porous media. The degradation is analyzed by passing the solution repeatedly through the medium at a constant flow velocity and the degraded solution is then characterized by porous media and opposed jets flows. When the polyacrylamide is dissolved in deionized water, it exhibits a gradual extension thickening in the flow through porous media and opposed jets. In this case, the polymer degrades as it passes through the porous medium even at relatively low flow rates. When the polyacrylamide is dissolved in an NaCl solution, it exhibits critical extension thickening in porous media flows, and it only degrades at Reynolds numbers that are higher than the onset of the extension thickening behavior. Chain degradation is therefore only encountered when extension thickening is produced. The results also show that the extent of degradation decreases as the pore size decreases.     

Foam electrospinning: A multiple jet,needle‐less process for nanofiber production

A multiple jet, needle‐less process to fabricate electrospun nanofibers from foamed columns, produced by injecting compressed gas through a porous surface into polymer solutions, capable of circumventing syringe electrospinning shortcomings such as needle clogging and restrictions in production rate is presented. Using polyvinyl alcohol and polyethylene oxide (PEO) as model systems, we identify key design, processing, and solution parameters for producing uniform fibers. Increasing electrode surface area produces thicker mats, suggesting charge distribution through the bulk foam facilitates electrospinning. Similar trends between foam and syringe electrospinning are observed for collection distance, electric field strength, and polymer concentration. Interestingly, the empirical correlation between polymer entanglement and fiber formation are found to be similar for both foam and traditional needle electrospinning, but the fiber crystallinity shows enhancement with foam electrospinning. In addition, foam electrospinning with a PEO‐nonionic surfactant system yields two orders of magnitude increase in production rate compared to syringe electrospinning. © 2014 American Institute of Chemical Engineers AIChE J, 60: 1355–1364, 2014     

聚合物驱注入压力设计计算

根据工程流体力学以及渗流力学,建立了聚合物驱油注入压力计算模型,给出了详细的计算步骤,以一口注聚井的数据为例,进行了聚合物驱注入过程中注入压力的分段计算,结果表明聚合物驱油注入压力包括克服地面配注管道摩阻以及聚合物溶液在地层渗流阻力所需的压力,注入压力损耗最大的是地层渗流压力,依次是孔眼压降,管流压降最小。