Polymer Flow Through Porous Media: Numerical Prediction of the Contribution of Slip to the Apparent Viscosity.

The flow of polymer solutions in porous media is often described using Darcy’s law with an apparent viscosity capturing the observed thinning or thickening effects. While the macroscale form is well accepted, the fundamentals of the pore-scale mechanisms, their link with the apparent viscosity, and their relative influence are still a matter of debate. Besides the complex effects associated with the rheology of the bulk fluid, the flow is also deeply influenced by the mechanisms occurring close to the solid/liquid interface, where polymer molecules can arrange and interact in a complex manner. In this paper, we focus on a repulsive mechanism, where polymer molecules are pushed away from the interface, yielding a so-called depletion layer in the vicinity of the wall. This depletion layer acts as a lubricating film that may be represented by an effective slip boundary condition. Here, our goal is to provide a simple mean to evaluate the contribution of this slip effect to the apparent viscosity. To do so, we solve the pore-scale flow numerically in idealized porous media with a slip length evaluated analytically in a tube. Besides its simplicity, the advantage of our approach is also that it captures relatively well the apparent viscosity obtained from core-flood experiments, using only a limited number of inputs. Therefore, it may be useful in many applications to rapidly estimate the influence of the depletion layer effect over the macroscale flow and its relative contribution compared to other phenomena, such as non-Newtonian effects

The effects of concentration and salinity on polymer adsorption isotherm at sandstone rock surface

Adsorption of hydrolyzed polyacrylamide (HPAM) polymers on sandstone rock surface was studied by static adsorption experiments. Total of 10 Runs of static experiments were conducted in test tubes by mixing the desired solution with crushed rock sample, at temperature of 25 °C, and salinity range from 0-4 wt%. The results are in conformity with Langmuir's isotherm. Ten different isotherms were generated at each Run. The initial polymer concentration was varied from 0.3-2.1 g/l. The effects of salinity have been studied by observation on Langmuir adsorption coefficients (Y and K). The results show that the adsorption coefficient (Y) was found to have linear relationship with salinity. The adsorption coefficient (K) was found to be related to salinity by a quadratic relationship

The onset of dilatant behaviour in non-inertial flow of dilute polymer solutions through channels with varying cross-sections

The apparent viscosity of dilute polymer solutions in non-inertial flows through channels consisting of successive short tubes or slits separated by expansions displays a marked divergence from shear-thinning power-law behaviour beyond a critical shear rate calculated for constricted sections. The product of this critical shear rate by the Rouse relaxation time was found to be nearly constant for various coil polymers, solvent viscosities and polymer concentrations, independently of the exact geometric shape of the channels. When the critical shear rate is reached, the maximum stretch rate in the converging sections is greater than the inverse of the Rouse relaxation time. An elongation of macromolecules is thus expected and the dilatant behaviour can be attributed to the increased viscous dissipation due to the elongated state of macromolecules in the converging parts of flow.La viscosité apparente de solutions diluées de polymère lors d'écoulements non inertiels dans des canaux constitués de tubes courts ou de fentes séparées par des expansions cesse de suivre un comportement pseudoplastique en loi puissance au-delà d'une vitesse de cisaillement critique calculée pour la section contractée. Le produit de cette vitesse de cisaillement critique par le temps de relaxation de Rouse est à peu près constant pour différents polymères en pelote, différentes viscosités du solvant et différentes concentrations en polymère, indépendamment de la forme géométrique exacte des canaux. Quand la vitesse de cisaillement critique est atteinte, la vitesse d'élongation maximale dans les sections convergentes de l'écoulement est supérieure à l'inverse du temps de relaxation de Rouse. On s'attend dans ces conditions à une élongation des macromolécules et on peut interpréter le comportement dilatant par l'augmentation de la dissipation visqueuse accrue par suite de l'état allongé des macromolécules dans les parties convergentes de l'écoulement

Polyelectrolyte Complexation At Oxide-Water Interfaces : Influence on Colloidal Stability Complexation de polyelectrolytes aux interfaces oxydes-eau : influence sur la stabilité colloidale

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Reduction of Polymer Adsorption on Reservoir Rocks

The adsorption properties of polyacrylamides and xanthans on mineral surfaces carrying silanol and aluminol groups such as sand and kaolinite are described. The influence of the main parameters such as the nature of adsorption sites, surface charge, chemical structure and conformation of polymer and interactions of mono- and divalent ions with polymer and mineral surface has been investigated and interpreted. Some operating parameters in polymer flooding such as pH and salinity of injected solution, the nature of the polymer and its degree of ionicity were found to be determining factors from the adsorption level. The results give key elements for reducing adsorption by a proper choice of polymer nature and ionicity and of injection conditions

Permeability Damage Due to Asphaltene Deposition : Experimental and Modeling Aspects Endommagement d'un milieu poreux par dépôts d'asphaltènes : expériences et modélisation

The flow properties of several asphaltenic crudes were studied at reservoir temperature in rocks of different morphology and mineralogy. The experiments performed showed a progressive reduction in permeability to oil during injection, varying in rate according to the system considered. The existence of organic deposits was verified by Rock-Evalpyrolysis measurements made on sections of samples taken at the end of flow at different distances from the entry face. This technique enables the profile of the deposits to be quantified. The interpretation of the permeability damage experiments and their simulation are treated by comparing the asphaltenes in oil to colloidal particles in suspension, capable of being deposited at the surface of the pores and thus reducing the permeability of the porous medium. The first simulations were carried out using the PARISIFP particle damage model, which has recently been extended to the case of multi-layer deposition. A satisfactory qualitative agreement is observed with the experimental results. Les propriétés d'écoulement de plusieurs bruts asphalténiques ont été étudiées à la température du réservoir d'origine dans des roches de morphologie et minéralogie différentes. Les expériences réalisées mettent en évidence une réduction progressive de la perméabilité à l'huile au cours de l'injection, plus ou moins rapide selon les cas. L'existence de dépôts organiques a été vérifiée par des mesures de pyrolyse Rock-Evaleffectuées sur des sections d'échantillons prélevées en fin d'écoulement à différentes distances de la face d'entrée. Cette technique permet de quantifier le profil des dépôts. L'interprétation des expériences de colmatage et leur simulation sont traitées en assimilant les asphaltènes dans l'huile à des particules colloïdales en suspension, susceptibles de se déposer à la surface des pores et ainsi de réduire la perméabilité du milieu poreux. Les premières simulations ont été réalisées en utilisant le modèle IFP d'endommagement particulaire PARIS , qui a été récemment généralisé au cas de dépôt en multicouches. On observe un accord qualitatif satisfaisant avec les résultats expérimentaux