Retention and Flow Characteristics of Polymer Solutions in Porous Media

1977 ◽  
Vol 17 (02) ◽  
pp. 111-121 ◽  
Author(s):  
J.G. Dominguez ◽  
G.P. Willhite
Keyword(s):  
Porous Media ◽  
Flow Rate ◽  
Polymer Solutions ◽  
Polymer Concentration ◽  
Flow Characteristics ◽  
Porous Matrix ◽  
Polymer Molecules ◽  
Partially Hydrolyzed Polyacrylamide ◽  
Hydrolyzed Polyacrylamide ◽  
Polymer Retention

Abstract Retention and flow characteristics of a solution containing Pusher 700, a high-molecular-weight, partially hydrolyzed polyacrylamide, were studied partially hydrolyzed polyacrylamide, were studied in an 86-md core made by compacting Teflon powder. The quantity, of polymer retained during linear displacement experiments ranged from 10 to 21 mu gm/gm for polymer concentrations of 100 to 500 ppm in 2-percent NaCl solutions. Nearly all retention ppm in 2-percent NaCl solutions. Nearly all retention was attributed to mechanical entrapment because of low polymer adsorption on the Teflon surface. Flow rate affected polymer retention. In increase in velocity was accompanied by polymer retention. Polymer was expelled when the flow rate was Polymer was expelled when the flow rate was reduced. Inaccessible pore volume was about 19 percent of the total pore volume. percent of the total pore volume.Resistance factors in different sections of the core ranged Pam 2 to 10 /or solutions of 100 to 500 ppm polymer concentration in 2-percent NaCl. ppm polymer concentration in 2-percent NaCl. Permeability reduction resulting from polymer Permeability reduction resulting from polymer retention produces the resistance factor in most of the core at a velocity of 3.2 ft/D. Resistance factors in the Teflon cores were two to three times lower than those reported for natural porous media where polymer is also retained by adsorption. Introduction The search for a low-cost, effective mobility control agent is currently focused on dilute aqueous solutions containing partially hydrolyzed polyacrylamides or polysaccharides. Rheological polyacrylamides or polysaccharides. Rheological properties have been studied, including the properties have been studied, including the effects of polymer concentration, shear rate, electrolyte concentration, and type of electrolyte. Correlation of rheological data and models with the flow behavior of polymer solutions in porous media has been complicated by the many interactions that occur between the complex porous matrix and the polymer solutions. Some data have been correlated using non-Newtonian rheological models to describe the variation of fluid viscosity with the apparent shear rate that the fluid experiences as it flows through the tortuous paths in porous media. These correlations have adjustable parameters determined from the particular set of parameters determined from the particular set of data used to develop the correlation. Investigators studying partially hydrolyzed polyacrylamide solutions observed apparent polyacrylamide solutions observed apparent viscosities 5 to 20 times the values measured in a conventional viscometer at the shear rates believed to exist in the porous media. These viscosity increases were not anticipated from the rheological behavior of the fluids. Pye introduced the concept of the resistance factor to quantify this effect. Burcik observed a decrease in the mobility of brine in a Berea sandstone disk that had been previously contacted with partially hydrolyzed previously contacted with partially hydrolyzed polyacrylamide. The mobility reduction persisted polyacrylamide. The mobility reduction persisted even after 100 PV of brine had been flushed through the disk. Burcik concluded that polymer molecules retained in the pore structure by adsorption or mechanical entrapment were hydrophillic and restricted the flow of water. Gogarty made an extensive experimental study of partially hydrolyzed polyacrylamide solutions in porous media and concluded that these polymer porous media and concluded that these polymer solutions reduced the permeability of the porous media. He noosed that polymer retention in natural cores occurred by mechanical entrapment and adsorption. Both mechanisms contributed to the resistance and residual or flushed resistance factors observed with polyacrylamide solutions. Other evidence of interactions between the polymer solution and the porous matrix was found. polymer solution and the porous matrix was found. Adsorption of polymer molecules on the surface of materials present in the porous matrix has been demonstrated in batch adsorption experiments. Material-balance calculations made on the streams entering and leaving porous media following step changes in concentrations show retention of polymer molecules in the porous media. polymer molecules in the porous media. A dependence of polymer retention on flow rate has been reported. Szabo devised a set of static and flow experiments in which polymer adsorption was held to a low level by using silica sand with a small surface area. Mechanical entrapment was found to be the dominant retention mechanism in short sand packs. packs. SPEJ P. 111

Effect of Concentration on HPAM Retention in Porous Media

SPE Journal ◽  
2014 ◽  
Vol 19 (03) ◽  
pp. 373-380 ◽  
Author(s):  
Guoyin Zhang ◽  
R.S.. S. Seright
Keyword(s):  
Porous Medium ◽  
Porous Media ◽  
Polymer Solution ◽  
Polymer Concentration ◽  
Retention Mechanism ◽  
Dynamic Measurements ◽  
Polymer Molecules ◽  
Adsorbed Polymer ◽  
Hydrolyzed Polyacrylamide ◽  
Polymer Retention

Summary This paper investigates the effect of hydrolyzed polyacrylamide (HPAM) polymer concentration on retention in porous media by use of both static and dynamic measurements. Consistent results by use of these two methods show that different polymer-retention behaviors exist in dilute, semidilute, and concentrated regions. In both the dilute and concentrated regions, polymer retention has little dependence on concentration. In contrast, in the semidilute region, polymer retention is concentration dependent. If a porous medium is first contacted sufficiently with dilute polymer solution to satisfy the retention, no significant additional retention occurs during exposure to higher HPAM concentrations. On the basis of the experimental results, a concentration-related retention mechanism is proposed that considers the orientation of the adsorbed polymer molecules and the interaction between molecular coils in solution. By use of this model, we explain why polymer retention does not show much dependence on concentration in the dilute and concentrated regimes. Further, in the semidilute region, we explain how moderate coil interactions lead to mixed adsorbed-polymer orientation and magnitude on rock surfaces, and retention becomes concentration dependent. In field applications of polymer and chemical floods, reduced polymer retention may be achieved by first injecting a low-concentration polymer bank.

Some Aspects of Polymer Retention in Porous Media Using a C14-Tagged Hydrolyzed Polyacrylamide

1975 ◽  
Vol 15 (04) ◽  
pp. 323-337 ◽  
Author(s):  
M.T. Szabo
Keyword(s):  
Porous Media ◽  
Oil Recovery ◽  
Pore Volume ◽  
Produced Water ◽  
Polymer Concentration ◽  
Oil Saturation ◽  
Polymer Flow ◽  
Hydrolyzed Polyacrylamide ◽  
Polymer Retention ◽  
Inaccessible Pore Volume

Abstract Numerous single-phase flow and oil-recovery tests were carried out in unconsolidated sands and Berea sandstone cores using C14-tagged, hydrolyzed polyacrylamide solutions. The polymer-retention polyacrylamide solutions. The polymer-retention data from these flow tests are compared with data obtained from static adsorption tests. Polymer concentrations in produced water in Polymer-flooding tests were studied using various Polymer-flooding tests were studied using various polymer concentrations, slug sizes, salt polymer concentrations, slug sizes, salt concentrations, and different permeability sands. Results show that polymer retention by mechanical entrapment had a dominant role in determining the total polymer retention in short sand packs. However, the role of mechanical entrapment was less in the large-surface-area Berea cores. In oil-recovery tests, high polymer concentrations were noted at water breakthrough in sand-pack experiments, an indication that the irreducible water was not displaced effectively ahead of the polymer slug. However, in similar tests with Berea cores, a denuded zone developed at the leading edge of the polymer slug. polymer slug. The existence of inaccessible pore volume to polymer flow is shown both in sand packs and in polymer flow is shown both in sand packs and in sandstone cores. Absolute polymer-retention values show an almost linear dependency on polymer concentration. The effect of polymer slug size on absolute polymer retention is also discussed. Distribution of retained polymer in sand packs showed an exponential decline with distance. The "dynamic polymer-retention" values in short sand packs showed much higher vales than the ‘static packs showed much higher vales than the’ static polymer-adsorption" values caused by mechanical polymer-adsorption" values caused by mechanical entrapment. The mechanism of polymer retention in silica sands and sandstones is described, based on the observed phenomenon. Introduction It is widely recognized that, as polymer solution flows in a porous medium, a portion of the polymer is retained. It is evident that both physical adsorption and mechanical entrapment contribute to polymer retention. The question of the relative importance of these retention mechanisms has not been studied adequately. The effect of residual oil saturation on polymer retention and the polymer retention during the displacement of oil from porous media has also been studied inadequately. Mungen et al. have reported a few data on polymer concentration in produced water in oil-recovery tests. However, no produced water in oil-recovery tests. However, no comparison was made between polymer retention at 100-percent water saturation and at partial oil saturation. It has been shown that the actual size of the flowing polymer molecules, with the associated water, can approach the dimensions of certain smaller pores found in porous media. Therefore, an inaccessible pore volume exists in which no polymer flow occurs. In this study, the existence polymer flow occurs. In this study, the existence of inaccessible pore volume is shown clearly, both in sand and sandstone. Although polymer-retention values have been reported for various conditions, correlation is difficult because of the differing conditions of measurements. The effect of slug size, polymer concentration, salinity, and type of porous media on polymer retention has not been systematically studied. The purpose of this study was to develop answers to these questions, rather than to provide adsorption data for actual field core samples. For this reason, unconsolidated silica sands were used in most of the experiments reported. This permitted identical, uniform single-layer and multilayer porous media to be constructed for repeated experiments under varying test conditions. Some experiments were also carried out in Berea sandstone cores to determine whether sand-pack results can be extrapolated to consolidated sandstones. Using a C 14-tagged polymer provided a very rapid, simple, and accurate polymer-concentration determination technique. SPEJ P. 323

Mechanical Degradation of Partially Hydrolyzed Polyacrylamide Solutions in Unconsolidated Porous Media

1976 ◽  
Vol 16 (04) ◽  
pp. 172-174 ◽  
Author(s):  
J.M. Maerker
Keyword(s):  
Porous Media ◽  
Flow Rate ◽  
Mobility Control ◽  
Mechanical Degradation ◽  
Degree Of Hydrolysis ◽  
Partially Hydrolyzed Polyacrylamide ◽  
Porosity Dependence ◽  
Flow Through ◽  
Unconsolidated Porous Media ◽  
Hydrolyzed Polyacrylamide

Introduction A number of recent papers have addressed the problem of mechanical degradation during injection problem of mechanical degradation during injection into oil reservoirs for secondary or tertiary recovery applications. Ref. 6 introduces and tests a mechanism for mechanical degradation of partially hydrolyzed polyacrylamide solutions and develops a procedure for predicting loss of mobility control in practical situations. The correlation of experimental degradation data on which this procedure depends is based on results of flow procedure depends is based on results of flow through consolidated sandstones only. Porosity was not a variable. Since many applications involve unconsolidated reservoirs, this paper investigates the effects of porosity, permeability, length, and flow rate on mechanical degradation of partially hydrolyzed polyacrylamide solutions in unconsolidated sand packs. A new correlation fitting both types of porous media is developed. The aforementioned correlation (Fig. 4 of Ref. 6) for screen-factor loss in saline polyacrylamide solutions depended on porosity through the correlating group, epsilonLD 1/3. However, the generality of the correlation with regard to porosity dependence was untested, since all the media used to induce degradation (mostly Berea outcrop sandstone) had a porosity of about 24 percent. Subsequent porosity of about 24 percent. Subsequent investigations have been conducted in sand packs with 600-ppm polyacrylamide concentrations in 3.0-percent NaCl plus 0.3-percent CaCl2 to test the porosity dependence and provide more realistic mechanicaldegradation data for application to unconsolidated reservoirs. EXPERIMENTAL PROCEDURE The polymer used was from the same commercially available stock used in Ref. 6, having an estimated average molecular weight between 5 and 7 million and a 20-percent degree of hydrolysis. Sand was packed by sifting into a brine-filled lucite cell designed to eliminate effects of possible degradation caused by a plastic retaining screen at the outlet face. Sand-grain density was assumed to be 2.65 gm/cc, and porosities were determined from weight/volume measurements of sand packed in a brine-filled graduated cylinder. Various sand-grain size fractions were obtained by dry-sieve separation on three different sand sources. The sand packs are described in Table 1. Notice that Sand Packs 1, 3, and 4 were obtained from narrow size ranges, while Sand Pack 5 was a deliberate, broad distribution. RESULTS Experimental screen-factor and viscosity losses induced by flow through the sand packs are analogous to those in Ref. 6 for consolidated sandstones; however, the curves are shifted to larger fluxes (volumetric flow rate divided by cylindrical cross-sectional area) because of higher permeabilities. Plotting screen-factor losses as a permeabilities. Plotting screen-factor losses as a function of the correlating group, epsilonLD 1/3, yields the curves in Fig. 1. The consolidated-sandstone correlation curve from Ref. 6 is reproduced here for comparison. Screen-factor losses resulting from mechanical degradation in unconsolidated porous media occur at larger values of epsilonLD 1/3 than in consolidated sandstones and are not well correlated; that is, this correlating group does not allow all screen-factor-loss data to converge on a single curve. SPEJ P. 172

Temperature Dependence of the Shear-Thinning Behavior o Partially Hydrolyzed Polyacrylamide Solution for Enhanced Oil Recovery

2020 ◽  
Vol 143 (6) ◽  
Author(s):  
Pan-Sang Kang ◽  
Jong-Se Lim ◽  
Chun Huh
Keyword(s):  
Temperature Dependence ◽  
Polymer Solution ◽  
Enhanced Oil Recovery ◽  
Oil Recovery ◽  
Polymer Concentration ◽  
Shear Thinning ◽  
Temperature Model ◽  
Polyacrylamide Solution ◽  
Partially Hydrolyzed Polyacrylamide ◽  
Hydrolyzed Polyacrylamide

Abstract The viscosity of injection fluid is a critical parameter that should be considered for the design and evaluation of polymer flood, which is an effective and popular technique for enhanced oil recovery (EOR). It is known that the shear-thinning behavior of EOR polymer solutions is affected by temperature. In this study, temperature dependence (25–70 °C) of the viscosity of a partially hydrolyzed polyacrylamide solution, the most widely used EOR polymer for oil field applications, was measured under varying conditions of the polymer solution (polymer concentration: 500–3000 ppm, NaCl salinity: 1000–10,000 ppm). Under all conditions of the polymer solution, it was observed that the viscosity decreases with increasing temperature. The degree of temperature dependence, however, varies with the conditions of the polymer solution. Martin model and Lee correlations were used to estimate the dependence of the viscosity of the polymer solution on the polymer concentration and salinity. In this study, we proposed a new empirical model to better elucidate the temperature dependence of intrinsic viscosity. Analysis of the measured viscosities shows that the accuracy of the proposed temperature model is higher than that of the existing temperature model.

Inaccessible Pore Volume in Polymer Flooding

1972 ◽  
Vol 12 (05) ◽  
pp. 448-452 ◽  
Author(s):  
Rapier Dawson ◽  
Ronald B. Lantz
Keyword(s):  
Porous Media ◽  
Mathematical Models ◽  
Pore Volume ◽  
Polymer Solutions ◽  
Polymer Flooding ◽  
Reservoir Rock ◽  
Front Edge ◽  
Polymer Molecules ◽  
The Core ◽  
Inaccessible Pore Volume

Abstract We have found that solutions of typical waterflooding polymers do not occupy all of the connected pore volume in porous media. The remainder of the pore volume is inaccessible to polymer. This inaccessible pore volume is occupied polymer. This inaccessible pore volume is occupied by water that contains no polymer, but is otherwise in equilibrium with the polymer solution. This allows changes in polymer concentration to be propagated through porous media more rapidly than propagated through porous media more rapidly than similar changes in salt concentration. At the front edge of a polymer bank the effect of inaccessible pore volume opposes the effect of adsorption and pore volume opposes the effect of adsorption and may completely remove it in some cases. This paper presents three experimental polymer floods showing the effect of inaccessible pore volume in the presence of varying amounts of adsorption. Results of these floods clearly show that about 30 percent of the connected pore volume in the rock samples used was not accessible to The polymer solutions. The changes required to include polymer solutions. The changes required to include inaccessible pore volume in mathematical models of polymer flow and in held prediction methods are discussed. Introduction One way o improving the mobility ratio during waterflooding operations is by addition of a water-soluble polymer to the flood water. Several different polymers have been proposed and a number of investigators have presented results on the behavior of these polymer solutions in porous media. In addition, mathematical models have been developed for predicting the field behavior of polymer flooding. In all these studies movement polymer flooding. In all these studies movement of the polymer bank through the reservoir rock is of great importance. One phenomenon that has been repeatedly observed in polymer flooding is the removal of polymer from solution by adsorption on the reservoir rock. As a polymer bank propagates through porous media, the polymer bank propagates through porous media, the front edge is gradually denuded of polymer. The amount of polymer lost from a bank may be large or small, depending on the nature of the polymer and rock surface. This loss of polymer must be measured and included in any realistic mathematical model of polymer behavior. It has been widely assumed that polymer behavior. It has been widely assumed that adsorption is the most significant factor causing polymer to propagate through porous media at a polymer to propagate through porous media at a velocity different from that of water. In this paper we present data that demonstrate that all of the pores may not be accessible to polymer molecules and that this "inaccessible polymer molecules and that this "inaccessible pore volume" can affect polymer propagation pore volume" can affect polymer propagation significantly. In addition to the experimental results, we discuss the changes in interpretation and in mathematical models that are required to include this phenomenon. EXPERIMENTAL The experiments described in this paper were single-phase displacement of polymer solutions through consolidated sandstone. All the cores were prepared by evacuating and saturating with brine; prepared by evacuating and saturating with brine; the pore volumes of the cores were measured at this time. The experimental floods reported here were then done in three steps.An "initial solution" was injected until the core was at complete equilibrium with that solution.A bank of a different solution was injected into the core.Injection of the initial solution was resumed and continued until the end of the experiment. During each experiment the effluent from the core was collected in small samples; the analyses of these samples for polymer and salt content gave the basic data which is presented here. In plotting the results we used a "concentration fraction" defined as (Ce -Ci)/(Cb -Ci), where C is concentration and the subscripts e, i and b refer to the effluent, initial inlet and bank inlet values, respectively. All the solutions used were mixed in distilled water; concentrations are given in weight percent or in ppm by weight. Two polymers were used; one was a polyacrylamide (Pusher 700, The Dow Chemical Co.); the other a polysaccharide (XC biopolymer, Xanco, Div. of Kelco Co.). SPEJ P. 448

Flow Characteristics of Dilute Polymer Solutions in Micro Tubes

2007 ◽  
Author(s):  
Keizo Watanabe ◽  
Satoshi Ogata ◽  
Munehiko Hirao
Keyword(s):  
Flow Rate ◽  
Polymer Solutions ◽  
Flow Characteristics ◽  
Fused Silica ◽  
Flow Rate Ratio ◽  
Distilled Water ◽  
Number Range ◽  
Micro Piv ◽  
Dilute Polymer Solutions ◽  
Piv Measurement

Pressure drops and velocity profiles for micro tubes were investigated for the laminar flow of distilled water and dilute polymer solutions. The test micro tubes were fused silica capillaries with diameters in the range of 50.2–251.8 μm, and a value of l/d (length/diameter) of about 340. By performing pressure drop measurements, it is shown that the experimental data agree well with the Hagen-Poiseuille equation in the case of Newtonian fluids. On the other hand, the flow rate of dilute polymer solutions increases relative to that of distilled water in the low Reynolds number range. The increased flow rate ratio is a maximum of about 15% in the case of d = 251.8 μm. For the result of the micro PIV measurement, however, there are few differences between the velocity profile of distilled water and the Peo 5 ppm solution.

scholarly journals An Overview on Polymer Retention in Porous Media

Energies ◽  
2018 ◽  
Vol 11 (10) ◽  
pp. 2751 ◽  
Author(s):  
Sameer Al-Hajri ◽  
Syed Mahmood ◽  
Hesham Abdulelah ◽  
Saeed Akbari
Keyword(s):  
Porous Media ◽  
Enhanced Oil Recovery ◽  
Oil Recovery ◽  
Polymer Flooding ◽  
Mobility Ratio ◽  
Reservoir Rock ◽  
Polymer Molecules ◽  
Modeling Techniques ◽  
Proper Estimation ◽  
Polymer Retention

Polymer flooding is an important enhanced oil recovery technology introduced in field projects since the late 1960s. The key to a successful polymer flood project depends upon proper estimation of polymer retention. The aims of this paper are twofold. First, to show the mechanism of polymer flooding and how this mechanism is affected by polymer retention. Based on the literature, the mobility ratio significantly increases as a result of the interactions between the injected polymer molecules and the reservoir rock. Secondly, to provide a better understanding of the polymer retention, we discussed polymer retention types, mechanisms, factors promoting or inhibiting polymer retention, methods and modeling techniques used for estimating polymer retention.

Prediction of Viscosity for Partially Hydrolyzed Polyacrylamide Solutions in the Presence of Calcium and Magnesium Ions

1981 ◽  
Vol 21 (05) ◽  
pp. 623-631 ◽  
Author(s):  
J.S. Ward ◽  
F. David Martin
Keyword(s):  
Ionic Strength ◽  
Oil Recovery ◽  
Divalent Cations ◽  
Polymer Concentration ◽  
Solution Viscosity ◽  
Shear Rates ◽  
Partially Hydrolyzed Polyacrylamide ◽  
Lower Shear ◽  
Total Ionic Strength ◽  
Hydrolyzed Polyacrylamide

Abstract Loss of solution viscosity in water of increasing ionic strength is a major problem encountered in the use of the partially hydrolyzed polyacrylamide polymers for improved oil recovery. It is recognized widely that the viscosity loss is more drastic in the presence of multivalent cations than is observed for sodium ions. There is, however, little information available on the relationships between total ionic strength, concentrations of multivalent cations, and solution viscosities.The purpose of this study is to establish relationships between total ionic strength, concentration of calcium or magnesium ions, polymer concentration, and the resulting viscosity for partially hydrolyzed polyacrylamides with varying degrees of hydrolysis. Solutions at constant ionic strength with varying ratios of calcium or magnesium to sodium ions are compared, and the loss of viscosity as a function of the fraction of divalent cations in the system is determined. For shear rates in the power-law region, the fractional loss in viscosity is a function of the fraction of multivalent cations and, in the range studied, is independent of the total ionic strength. A more complicated relationship is found at lower shear rates where the fractional viscosity loss does vary with total ionic strength.The relationship in the power-law region should prove valuable in predicting viscosities on the basis of the dependence of viscosity on ionic strength and on multivalent cation concentration at a single ionic strength, eliminating the need for many individual measurements of viscosity. More work is needed before useful predictions will be possible at lower shear rates. Introduction Partially hydrolyzed polyacrylamide (HPAM) polymers are currently the most widely used mobility control polymers for secondary and tertiary oil recovery. Small quantities of HPAM can increase the viscosity of water by two or more orders of magnitude in the absence of added electrolytes. This phenomenal increase in viscosity results from the extremely high molecular weight of these polymers and repulsion between the negative charges along the polymer chain, resulting in maximum chain extension. The latter mechanism leads to one of the greater disadvantages of using HPAM in an oil reservoir. In the presence of the electrolyte molecules in typical oilfield brines, negative charges along the polymer chain are screened from each other by association with cations from the solution. The polymer chains no longer are extended fully, and solution viscosity decreases. Mungan observed that divalent cations have a more pronounced effect on viscosity than univalent cations when compared on the basis of equal weights of the chloride salts.Viscosities have been reported for HPAM solutions in sodium chloride brines of varying strength as well as for solutions in brines containing CaCl2 or MgCl2. Some viscosities also have been reported for solutions in brines containing both sodium and calcium ions, but no systematic study of the viscosity trends in brines with more than one type of cation has been reported.The purpose of this study is to investigate HPAM solutions with varying ratios of univalent to divalent cations and to establish trends of the solution viscosities for different values of degree of polymer hydrolysis, polymer concentration, and total ionic strength. Such trends are useful for predicting a wide range of viscosities from a few basic measurements. SPEJ P. 623^

Flow Behavior Through Porous Media and Microdisplacement Performances of Hydrophobically Modified Partially Hydrolyzed Polyacrylamide

SPE Journal ◽  
2016 ◽  
Vol 21 (03) ◽  
pp. 688-705 ◽  
Author(s):  
Yongjun Guo ◽  
Jun Hu ◽  
Xinmin Zhang ◽  
Rusen Feng ◽  
Huabing Li
Keyword(s):  
Pore Size ◽  
Flow Behavior ◽  
Polymer Concentration ◽  
Molecular Structures ◽  
Microporous Membranes ◽  
Series Connection ◽  
Partially Hydrolyzed Polyacrylamide ◽  
Hydrophobically Modified ◽  
Monomer Content ◽  
Hydrolyzed Polyacrylamide

Summary To investigate the relationship between the flow behavior and microdisplacement performance and the molecular structures, especially associating monomer content, of hydrophobically modified partially hydrolyzed polyacrylamides (HMHPAMs) with varied associating monomer content, compared with that of partially hydrolyzed polyacrylamide (HPAM), a series of experiments were conducted that involved the filtration through screen viscometer, nucleopore membrane, and series-connection microporous membranes; the flow through three serial mounted artificial cores; and the displacement in the microetching model. The screen factors and the hydrodynamic sizes of polymers were obtained by screen viscometer and nucleopore membrane, respectively. The results show that the screen factors and hydrodynamic sizes of HMHPAMs were much-more sensitive to the polymer concentration, filtration pressure, and associating monomer content than HPAM. Moreover, the filtration experiment through series-connection microporous membranes indicates that there were moderate associating monomer content or greater flow pressure or pore size for HMHPAMs to easily pass and obtain equivalent differential pressure between membranes, which implies that the compatibility between the pore size and the hydrodynamic sizes of the microstructures is the most-important factor for the injectivity of HMHPAMs. The resistance factor (RF) established by HMHPAMs through three serial mounted artificial cores notably tended to be higher than HPAMs, and the HMHPAMs with higher associating monomer content could generate a greater RF. In contrast, when the associating monomer content was low enough and the permeability was high enough, the flow could obtain equilibrium easily and the RFs were almost in accordance, which indicate there was moderate associating monomer content for HMHPAMs to propagate deep into the cores. At the same viscosity, HMHPAMs had better microdisplacement efficiency than glycerol (no effect) and HPAM (a small portion) for displacing the residual oil trapped in the “dead” ends of flow channel. The pilot tests of the associative polymer AP-P4, which was developed for Bohai oil fields, have demonstrated the great application potential of HMHPAMs for enhanced oil recovery (EOR).

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