New Insights Into Polymer Rheology in Porous Media

SPE Journal ◽  
2010 ◽  
Vol 16 (01) ◽  
pp. 35-42 ◽  
Author(s):  
R.S.. S. Seright ◽  
Tianguang Fan ◽  
Kathryn Wavrik ◽  
Rosangela de Carvalho Balaban
Keyword(s):  
Porous Media ◽  
Oil Recovery ◽  
Shear Thickening ◽  
Shear Thinning ◽  
Mechanical Degradation ◽  
Polymer Rheology ◽  
Resistance Factors ◽  
Polymer Component ◽  
Flow Through ◽  
Hydrolyzed Polyacrylamide

Summary This paper clarifies the rheology of xanthan and partially hydrolyzed polyacrylamide (HPAM) solutions in porous media, especially at low velocities. Previous literature reported resistance factors (effective viscosities in porous media) and an apparent shear thinning at low fluxes that were noticeably greater than what is expected on the basis of viscosity measurements. The polymer component that causes the latter behavior is shown to propagate quite slowly and generally will not penetrate deep into a formation. Particularly for HPAM solutions, this behavior can be reduced or eliminated for solutions that experience mechanical degradation or flow through a few feet of porous rock. Under practical conditions where HPAM is used for enhanced oil recovery (EOR), the degree of shear thinning is slight or nonexistent, especially compared to the level of shear thickening that occurs at high fluxes.

scholarly journals Polymer Injectivity: Investigation of Mechanical Degradation of Enhanced Oil Recovery Polymers Using In-Situ Rheology

Energies ◽  
2018 ◽  
Vol 12 (1) ◽  
pp. 49 ◽  
Author(s):  
Badar Al-Shakry ◽  
Tormod Skauge ◽  
Behruz Shaker Shiran ◽  
Arne Skauge
Keyword(s):  
Porous Media ◽  
Enhanced Oil Recovery ◽  
Oil Recovery ◽  
Shear Thickening ◽  
Water Soluble ◽  
High Rate ◽  
Low Flow ◽  
Mechanical Degradation ◽  
Flow Rates

Water soluble polymers have attracted increasing interest in enhanced oil recovery (EOR) processes, especially polymer flooding. Despite the fact that the flow of polymer in porous medium has been a research subject for many decades with numerous publications, there are still some research areas that need progress. The prediction of polymer injectivity remains elusive. Polymers with similar shear viscosity might have different in-situ rheological behaviors and may be exposed to different degrees of mechanical degradation. Hence, determining polymer in-situ rheological behavior is of great significance for defining its utility. In this study, an investigation of rheological properties and mechanical degradation of different partially hydrolyzed polyacrylamide (HPAM) polymers was performed using Bentheimer sandstone outcrop cores. The results show that HPAM in-situ rheology is different from bulk rheology measured by a rheometer. Specifically, shear thickening behavior occurs at high rates, and near-Newtonian behavior is measured at low rates in porous media. This deviates strongly from the rheometer measurements. Polymer molecular weight and concentration influence its viscoelasticity and subsequently its flow characteristics in porous media. Exposure to mechanical degradation by flow at high rate through porous media leads to significant reduction in shear thickening and thereby improved injectivity. More importantly, the degraded polymer maintained in-situ viscosity at low flow rates indicating that improved injectivity can be achieved without compromising viscosity at reservoir flow rates. This is explained by a reduction in viscoelasticity. Mechanical degradation also leads to reduced residual resistance factor (RRF), especially for high polymer concentrations. For some of the polymer injections, successive degradation (increased degradation with transport length in porous media) was observed. The results presented here may be used to optimize polymer injectivity.

Shear Degradation of Partially Hydrolyzed Polyacrylamide Solutions

1975 ◽  
Vol 15 (04) ◽  
pp. 311-322 ◽  
Author(s):  
J.M. Maerker
Keyword(s):  
Oil Recovery ◽  
Polymer Solutions ◽  
Significant Loss ◽  
Mobility Control ◽  
Mechanical Degradation ◽  
Elastic Solids ◽  
Shear Degradation ◽  
Flow Through ◽  
Hydrolyzed Polyacrylamide ◽  
Mobility Reduction

Abstract Partially hydrolyzed polyacrylamide solutions are highly shear degradable and may lose much of their effectiveness in reducing water mobility when sheared by flow through porous rock in the vicinity of an injection well. Degradation is investigated by forcing polymer solutions, prepared in brines of various salinities, through consolidated sandstone plugs differing in length and permeability, over a plugs differing in length and permeability, over a wide range of flow rates. A correlation for degradation based on a theoretical viscoelastic fluid model is developed that extends predictive capability to situations not easily reproduced in the laboratory. Mobility-reduction losses in field cores at reservoir flow rates are measured following degradation and are found to depend strongly on formation permeability. Consideration of field applications shows that injection into typical wellbore geometries can lead to more than an 80-percent loss of the mobility reduction provided by undegraded solutions. Also discussed are consequences for incremental oil recovery and the possibility of injecting through propped fractures. possibility of injecting through propped fractures Introduction Susceptibility of commercially available, partially hydrolyzed polyacrylamides to mechanical, or shear, degradation represents a serious problem regarding their applicability as mobility-control fluids for secondary and tertiary oil recovery applications. The approach taken in this work assumes that surface handling equipment in the field (pumps, flow controllers, etc.) have been adequately designed to minimize effects of shear degradation in all operations preceding actual delivery of the polymer solution to the sand face. The remaining problem is to assess the mechanical degradation a polymer solution experiences when it enters the porous matrix at the high fluxes prevailing around injection wells. Ability to predict the degree of mobility-control loss based on a laboratory investigation of the relevant parameters is desirable. White et al. were the first to attempt prediction of matrix-induced degradation, but the result was only a recommended injection-rate limit for minimizing polymer degradation for two specific wellbore completions. More recent papers offer limited data supporting the contention that matrix-induced degradation of polyacrylamide solutions results in significant loss polyacrylamide solutions results in significant loss of mobility control . This paper investigates the cause of mechanical degradation in dilute polymer solutions and presents experimental data on the effects of polymer concentration, water salinity, permeability, flow rate, and flow distance. permeability, flow rate, and flow distance. Several interesting and unexpected conclusions are drawn from the results. BACKGROUND - THEORETICAL CONCEPT The mechanical degradation of polymer solutions occurs when fluid stresses developed during deformation, or flow, become large enough to break the polymer molecular chains. Historically, the feeling has been that shearing stresses in laminar shear flow or turbulent pipe flow were responsible for chain scission. However, recent data reported by Culter et al. suggest that degradation of viscoelastic polymer solutions in capillary tubes may be dominated by large elongational or normal caresses occurring at the entrance to the squared-off capillaries. Such stresses result from Lagrangian unsteady flow, or elongational deformation, at the tube entrance. Flow through porous media also generates velocity fields that are sufficiently unsteady, in the Lagrangian sense, to lead one to anticipate large viscoelastic normal stresses. Viscoelastic fluids are materials that behave like viscous liquids at low rates of deformation and partially like elastic solids at high rates of partially like elastic solids at high rates of deformation. Several constitutive models are available for describing the stress-strain behavior of such fluids. SPEJ P. 311

scholarly journals Polymer Injectivity: Investigation of Mechanical Degradation of EOR Polymers Using In-Situ Rheology

2018 ◽  
Author(s):  
Badar Al-Shakry ◽  
Tormod Skauge ◽  
Behruz Shaker Shiran ◽  
Arne Skauge
Keyword(s):  
Porous Media ◽  
Oil Recovery ◽  
Flow Characteristics ◽  
Shear Thickening ◽  
Water Soluble ◽  
High Rate ◽  
Low Flow ◽  
Mechanical Degradation ◽  
Flow Rates

Water soluble polymers have gained an increasing interest in enhanced oil recovery (EOR) processes, especially as polymer flooding. Despite the fact that the flow of polymer in porous medium has been a research subject for many decades with numerous publications, there are still some research areas that need progress. The prediction of polymer injectivity remains elusive. Polymers with similar shear viscosity might have different in-situ rheological behaviors and may be exposed to different extent of mechanical degradation. Hence, determining polymer in-situ rheological behavior is of great significance for defining its utility. In this study, an investigation of rheological properties and mechanical degradation of different HPAM (partially hydrolyzed polyacrylamide) polymers was performed using Bentheimer sandstone outcrop cores. Results show that, HPAM in-situ rheology is different from bulk rheology measured in rheometer. Specifically, shear thickening behavior occurs at high rates, and near-Newtonian behavior is measured at low rates in porous media. This deviates strongly from measurements in the rheometer. Polymer molecular weight and concentration influence its viscoelasticity and subsequently its flow characteristics in porous media. Exposure to mechanical degradation by flow at high rate through porous media leads to significant reduction in shear thickening and thereby improved injectivity. More importantly, the degraded polymer maintained in-situ viscosity at low flow rates indicating that improved injectivity can be achieved without compromising viscosity at reservoir flow rates. This is explained by reduction in viscoelasticity. Mechanical degradation also leads to reduced residual resistance factor (RRF), especially for high polymer concentrations. For some of the polymer injections, successive degradation (increased degradation with transport length in porous media) was observed. The results presented here may be used to optimize polymer injectivity.

scholarly journals Impact of Mechanical Degradation on Polymer Injectivity in Porous Media

2018 ◽  
Author(s):  
Badar Al-Shakry ◽  
Tormod Skauge ◽  
Behruz Shaker Shiran ◽  
Arne Skauge
Keyword(s):  
Porous Media ◽  
Oil Recovery ◽  
Polymer Solutions ◽  
Shear Thickening ◽  
Economic Cost ◽  
High Viscosity ◽  
Polymer Flooding ◽  
Mechanical Degradation ◽  
Thickening Behavior

Polymer flooding is an established enhanced oil recovery (EOR) method, still many aspects of polymer flooding are not well understood. This study investigates the influence of mechanical degradation on flow properties of polymers in porous media. Mechanical degradation due to high shear forces may occur in the injection well and at the entrance to the porous media. The polymers that give high viscosity yields at a sustainable economic cost are typically large, MW > 10 MDa, and have wide molecular weight distributions. Both MW and the distributions are altered by mechanical degradation, leading to changes in the flow rheology of the polymer. The polymer solutions were subjected to different degrees of pre-shearing and pre-filtering before injected into Bentheimer outcrop sandstone cores. Rheology studies of injected and produced polymer solutions were performed and interpreted together with in-situ rheology data. The core floods showed a predominant shear thickening behavior at high flow velocities which is due to successive contraction/expansion flow in pores. When pre-sheared, shear thickening was reduced but with no significant reduction in in-situ viscosity at lower flow rates. This may be explained by reduction in the extensional viscosity. Furthermore, the results show that successive degradation occurred which suggests that the assumption of the highest point of shear which determines mechanical degradation in a porous media does not hold for all field relevant conditions.

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.

Flow Behavior and Viscous-Oil-Microdisplacement Characteristics of Hydrophobically Modified Partially Hydrolyzed Polyacrylamide in a Repeatable Quantitative Visualization Micromodel

SPE Journal ◽  
2017 ◽  
Vol 22 (05) ◽  
pp. 1448-1466 ◽  
Author(s):  
Yongjun Guo ◽  
Yan Liang ◽  
Miao Cao ◽  
Rusen Feng ◽  
Xinmin Zhang ◽  
...  
Keyword(s):  
Oil Recovery ◽  
Flow Behavior ◽  
Resistance Factors ◽  
Partially Hydrolyzed Polyacrylamide ◽  
Viscous Oil ◽  
Hydrophobically Modified ◽  
Quantitative Visualization ◽  
Monomer Content ◽  
Hydrolyzed Polyacrylamide ◽  
Flow Experiments

Summary To profoundly investigate the flow behavior and viscous-oil-microdisplacement characteristics of hydrophobically modified partially hydrolyzed polyacrylamides (HMHPAMs) as well as the effect of associating monomer content on those behaviors and characteristics, compared with partially hydrolyzed polyacrylamide (HPAM), the flow experiments through three serial mounted flat-sand-inclusion micromodels and the viscous-oil-microdisplacement experiments in both homogeneous and interstratified connected heterogeneous repeatable quantitative visualization micromodels were conducted by use of a series of polymers with varied associating monomer content (0–1.0 mol%) at similar viscosity within all shear rates concerned. The results obtained from flow experiments show that the resistance factors (RFs) and residual resistance factors (RRFs) generated by HMHPAMs were noticeably higher than those of HPAM, and the RFs and RRFs exhibited significant permeability dependence and increased with associating monomer content. The greater RFs and RRFs for associative polymer might not be mainly caused by polymer adsorption or retention but mostly caused by increasing aggregate sizes. At concerned permeabilities (1.1–6.1 µm2), all injections of HMHPAMs could tend to be stable, which indicates that all HMHPAMs could propagate deep into the porous media. The viscous-oil-microdisplacement experiments regarding the visualization micromodels with varied permeabilities (and permeability contrasts) provide new insights into the viscous-oil-microdisplacement characteristics of HMHPAMs, such as the piston-like displacement and profile modification. In homogeneous models, under different permeabilities (1.1–6.1 µm2), the variations of final viscous-oil recovery first increased and then decreased as a function of increasing hydrophobe content, and the hydrophobe content of the polymer to obtain maximum oil recovery enhanced with increasing permeability. This might qualitatively indicate that a constant permeability matches an optimal content of hydrophobic groups. At permeability contrast of approximately three, the HMHPAM with lower hydrophobe content (0.2 mol%) could obtain the maximum viscous-oil recovery. In contrast, the maximum viscous-oil recovery was achieved by the HMHPAM with higher hydrophobe content (1.0 mol%) at a contrast of approximately five. The HMHPAM with higher content of hydrophobic groups is suitable for the significant heterogeneity.

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

Sign in / Sign up

Export Citation Format

Share Document